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Aim: The application of compressed sensing (CS) has enabled breath-hold 3D-MRCP with a shorter acquisition time in clinical practice. Introduction: To compare the image quality of breath-hold (BH) and respiratory-triggered (RT) 3D-MRCP with or without CS application in the same study population. Methods: In this retrospective study, from February to July 2020, a total of 98 consecutive patients underwent four different acquisition types of 3D-MRCP.; 1) BH MRCP with the generalized autocalibrating partially parallel acquisition (GRAPPA) (BH-GRAPPA), 2) RT-GRAPPA-MRCP, 3) RT-CS-MRCP and 4) BH-CS-MRCP. Relative contrast of common bile duct, 5-scale visibility score of biliary pancreatic ducts, 3-scale artifact score and 5-scale overall image quality score were evaluated by two abdominal radiologists. Results: Relative contrast value was significantly higher in BH-CS or RT-CS than in RT-GRAPPA (0.90 ± 0.057 and 0.89 ± 0.079, respectively, vs. 0.82 ± 0.071, p < 0.01) or BH-GRAPPA (vs. 0.77 ± 0.080, p < 0.01). The area affected by artifact was significantly lower in BH-CS among 4 MRCPs (p < 0.08). Overall image quality score in BH-CS was significantly higher than BH-GRAPPA (3.40 vs. 2.71, p < 0.01). There were no significant differences between RT-GRAPPA and BH-CS (vs. 3.13, p = 0.67) in overall image quality. Conclusion: In this study, our results revealed BH-CS had higher relative contrast and comparable or superior image quality among four MRCP sequences.

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.

Hazardous gases threaten human health and the environment due to their toxicity and flammability. Managing such risks requires reliable gas detection techniques. However, accurate detection of target environmental gases remains challenging. Recent advances in materials science have enabled the combination of molecular separation membranes with chemical sensors to achieve high selectivity in the detection of target gas molecules. Herein, we discuss the underlying gas separation mechanisms for different types of membrane overlayers, including graphene oxide, metal-organic frameworks, and metal oxides, as well as their integration with sensing materials. Furthermore, we discuss the relationship between sensing performance and surface chemistry, catalytic properties, and membrane nanostructure. We conclude by highlighting future directions for selective detection of environmental gas species.

The ability to fundamentally describe nanoparticle (NP) transport in the subsurface underpins environmental risk assessment and successful material applications, including advanced remediation and sensing technologies. Despite considerable progress, our understanding of NP deposition behavior remains incomplete as there are conflicting reports regarding the effect of fluid flow velocity on attachment efficiency. To directly address this and more accurately describe NP attachment behavior, we have developed a novel protocol using a quartz crystal microbalance with dissipation monitoring (QCM-D) to separate and individually observe deposition mechanisms (diffusion and sedimentation), providing in situ, real-time information about particle diffusion (from the bulk liquid to solid surface). Through this technique, we have verified that the approaching velocity of NPs via diffusion increases (0.8-6.7 μm/s) with increasing flow velocity (6.1-106.0 μm/s), leading to an increased NP kinetic energy, thus affecting deposition processes. Further, in the presence of a secondary energy minimum associated with organic surface coatings, secondary minimum deposition decreases and primary minimum deposition increases with the flow velocity. NPs deposited at the primary minimum are relatively more resistant to hydrodynamic energies (including detachment associated energies), resulting in an increase of observed attachment efficiencies. Taken together, this work not only describes a novel method to delineate and quantify physical processes underpinning particle behavior but also provides direct measurements regarding key factors defining the relationship(s) of flow velocity and particle attachment. Such insight is valuable for next-generation fate and transport model accuracy, especially under unfavorable attachment regimes, which is a current and critical need for subsurface material applications and implication paradigms.

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.

Surface-functionalized Mn–Fe oxide nanocrystals (NCs) were evaluated for single- and multi-sorbate scenarios considering As(V), Cr(VI), and U(VI) in varied water chemistries (deionized (DI), ground, and sea water) at pH 7.0. Multi-sorbate scenarios were further examined for competitive and/or cooperative effects. Precisely synthesized manganese ferrite (MnFe2O4) NCs were compared with iron oxide (Fe3O4) and manganese oxide (MnxOy) nanocrystal cores in terms of sorption capacities and colloidal stabilities. Positively charged cetyltrimethylammonium bromide (CTAB) and negatively charged oleyl phosphate (OP) were evaluated and compared as organic coatings. MnFe2O4 NCs exhibited both enhanced sorption performance and colloidal stability compared with Fe3O4 and MnxOy NC cores when functionalized with the same surfactant coating. For MnFe2O4 NCs, maximum sorption of As(V), Cr(VI), and U(VI) were observed to be 2.62, 3.43, and 4.27 mmol g−1, respectively (in DI water). Relative sorption capacity enhancement (compared with Fe3O4 and MnxOy) is due to increased surface grafting densities of MnFe2O4 NCs, providing a larger number of sorption sites (functional group) for target sorbates and higher repulsive energy (osmotic and elastic–steric interaction) for increased stability, and thus maintaining available surface area. For As(V) and Cr(VI) multi-sorbate systems, all materials evaluated preferentially adsorbed As(V) over Cr(VI). This preference was further investigated and observed using a novel quartz crystal microbalance (QCM) technique.

The application of positively charged polymers is a common treatment strategy for the sorption and separation of dissolved hexavalent chromium Cr(VI). In particular, polyethylenimine (PEI) has been demonstrated as an effective polymer for Cr treatment due to abundant amine groups and cost-effectiveness. However, PEI as a photoactive polymer has not been previously explored for Cr treatment. Toward this, we demonstrate the significant photoactive potential of PEI for Cr sorption and reduction [to Cr (III)], delineating amine structure-function relationships. Overall, Cr(VI) photoreduction is enhanced dramatically as a function of amine group density. Additionally, among the types of amine groups evaluated, tertiary amines are observed to be the most reactive followed by secondary and primary amines. When PEI is incorporated onto graphene oxide (GO) as a stabilizing scaffold, mass loading of PEI is a key variable for Cr(VI) treatment performance, which is observed to be a function of PEI molecular weight and oxidation extent of GO. Finally, when combined with magnetic nanomaterials, low energy, high efficiency separation, and reuse are demonstrated. For these, sorption-based separation processes maintained excellent performance over five cycles. Taken together, this work demonstrates that PEI can serve as highly effective, multifunctional material coating(s) not only for chromium treatment but potentially for other oxidized aqueous species as well.

Inorganic-organic nanocomposites, typically as an inorganic core with surface organic coating(s), have received interest as potential platform materials for sensor, catalyst, sorbent, and environmental applications, among others. Here, we describe the critical role of organic surface coatings with regard to the colloidal stability of engineered manganese oxide nanoparticles (MnxOy NPs). Specifically, we prepared libraries of monodisperse MnxOy NPs with a serial selection of surface coatings (stearic acid (SA), oleic acid (OA), poly(maleic anhydride-alt-1-octadecene) (PMAO), linear polyethyleneimine (LPEI), and multibranched polyethyleneimine (BPEI)), which were chosen based on comparable structure(s) and functional group(s). We systematically evaluated the role of surface organic coatings via critical coagulation concentrations (CCCs), which were compared with theoretical calculations (Schulze-Hardy rule). Through a newly developed light scattering protocol, we observed that the effective density of nanoclusters can exceed NPs' primary (bulk) density depending on the open space(s) within organic coatings. Interestingly, PMAO-coated NPs were more stable at the point of zero charge (PZC) than at neutral pH (pH 7), despite the loss of effective surface charge potential. CCC was 334 mM in NaCl and 1.5 mM in CaCl2 at pH 7, compared to CCC values of 807 mM in NaCl and 210 mM in CaCl2 at PZC. This increase in stability is due to polymer (re)configuration (at PZC), which was further confirmed with a quartz crystal microbalance-based technique to evaluate surface-based polymer dynamics. Taken together, this work quantifies the role of organic coating dynamics, including structure, grafting density, and configuration on the colloidal stability of organic-coated NPs.

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.

In this work, we have developed and characterized flux-enhanced graphene oxide laminate (GOL) membranes by increasing interlayer (layer-to-layer) spacing using multibranched polyethylenimine (PEI) polymers with varied molecular weights and by controlling the graphene oxide (GO) oxidation extent. For these assemblies, water flux was demonstrated to increase by as much as ca. 30-fold compared to GO only laminate controls. PEI-embedded GOL membranes also had better methyl orange (MO) rejection performance than GO laminate controls due to the dilution effects (i.e., water is transported through the assembly much faster than MO). Further, boron removal is demonstrated via functionalized PEI with d-glucono-1,5-lactone, containing a high density of boron chelating groups, which can also be recycled/recovered with high efficiency.

Inorganic–organic nanoscale materials have recently received significant interest as tunable, next generation, sorbents for the separation of metal and metalloid contaminants, including arsenic (As) and chromium (Cr), among others. In this work, we have designed and synthesized IONCs coated with specific functionalized organic materials with the goal of variable explicit evaluation. Specifically, single domain, superparamagnetic, monodisperse IONCs were synthesized and transferred into water via surface functionalization by ligand exchange and encapsulation methods. The as synthesized hybrid materials showed high performance for both As(V) and Cr(VI) sorption when nanocrystals are coated with positively charged organic surface coatings such as polyethyleneimine (PEI) and cetyltrimethylammonium bromide (CTAB). IONC cores coated with negatively charged organic coating materials (polyethyleneglycol (PEG), oleic acid (OA), sodium dodecyl sulfate (SDS)) and silica (SiO2) demonstrated significantly lower sorption capacities. When silica coated IONCs (Fe3O4@SiO2, core–shell materials) were surface coated with PEI, sorption capacities for As(V) and Cr(VI) of Fe3O4@SiO2@PEI are comparable to Fe3O4@PEI, underscoring the importance of surface coating functionality. To complement these studies, real-time sorption behavior of As(V) and Cr(VI) with PEI was explored by quartz crystal microbalance with dissipation (QCM-D).

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...

Overview This chapter provides an overview and outlook of nanotechnology’s enabling roles in developing effective environmental remediation processes. Nanotechnology has the potential to substantially improve environmental remediation technologies. Here, instead of an exhaustive review of all developments related to nano-enabled environmental remediation processes/technologies, we present a brief overview and then specific comparison(s) between the two most common application approaches—individual (free) nanoparticles and those systems with integrated nanomaterials/nanotechnology. Specifically, we review examples of metal oxide nanoparticles (as nano-adsorbents) and graphene oxide enabled membranes to illustrate key technological aspects regarding their application potential in environmental remediation. Lastly, we highlight three key steps to further advance material development: the establishment of structure-property-function relationships, delineating the effects of environmental factors and the addressing of potential risk issues.

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.

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.

Developments in nanoscale engineering now allow for molecular scale optimization of reactivity, sorption, and magnetism, among other properties, for advanced, material-based environmental applications, including sorption, separation, and sensing of radionuclides. Herein, we describe novel, monodisperse nanoscale manganese ferrite crystals (MnFe2O4) for ultra-high capacity environmental sorption and subsequent separation of uranyl in water. System optimization was explored as a function of nanocrystal (core) composition, surface coating(s), and water chemistry. 11 nm MnFe2O4 nanocrystals, which were colloidally stabilized via engineered oleyl-based surface bilayers, demonstrate extreme, yet specific, uranium binding capacities while remaining monomerically stable under environmentally relevant conditions (water chemistries), which are key for application. In particular, MnFe2O4 cores with oleyl phosphate (as the outer facing layer) bilayers demonstrate preferential uranium binding of >150% (uranium weight)/(particle system weight) while being highly water stable in elevated ionic strengths/types and pH (up to 235.4 ppm (10.24 mM) of NaCl and 51.3 ppm (1.28 mM) of CaCl2, in addition to 60 ppm of uranyl, pH 5–9). Further, when normalized for size and surface coatings, MnFe2O4 nanocrystals had significantly enhanced sorption capacities compared to Mn2FeO4, Fe3O4 and manganese oxide core analogs. Mechanistically, we demonstrate that observed uranium sorption enhancement is due not only to thermodynamically favorable interfacial interactions (for both particle and selected bilayer coatings), but also due to significant uranyl reduction at the particle interface itself. Uranium sorption capacities for optimized systems described are the highest of any material reported to date.

For the first time, this work develops and demonstrates precisely engineered manganese oxide nanoscale particles for the sorption of uranium, as uranyl, in water. Size controlled monodisperse nanocrystalline manganese oxides (12 to 28 nm) were systematically synthesized via thermal decomposition of manganese oleate and phase-transferred into water by ligand exchange and bilayer stabilization methods. Resulting monodisperse suspensions demonstrate significantly enhanced uranyl adsorption as a function of size, surface coating chemistries, and solution pH. In particular, 12 nm particles coated with the unsaturated–unsaturated carbon chains linked bilayers, (e.g. oleic acid-oleyl phosphate linked bilayer coatings) have binding capacities well over 600 mg U per g of Mn, which is the highest reported uranium sorption capacity for any manganese based sorbent to date. Further, we spectrally identify significant uranyl reduction as part of the adsorption mechanism(s) for high capacity materials. Last, oleyl-based (phosphate and carboxylic) functionalized bilayered nanocrystals were extremely stable in the presence of high ionic strength/type (>800 mM); calcium (>19 mM), including the presence of uranyl cations (from 0.1 to 60 ppm). Taken together, these data demonstrate the potential for engineered monodisperse manganese oxide nanocrystals as ultra-high capacity platform sorbent materials for uranium separation at environmentally relevant ionic strengths and pH.

The sorption properties of TiO2 nanoparticles (NPs) on sand were investigated in the presence of Suwannee River humic acid (SRHA) as a surrogate for natural organic matter. SRHA drastically reduced the sorption preference regardless of the initial pH and ionic strength of the solution. Despite the higher SRHA loading onto sand versus the TiO2 NPs, the consequent zeta (ζ)-potential drop was more significant in the TiO2 NPs, indicating that the decreased sorption should be primarily ascribed to the fraction of SRHA sorbed onto the TiO2 NP surfaces. The hindering effect of SRHA on the sorption increased with SRHA concentration, but stabilized at the concentration equivalent to full surface coverage of the TiO2 NPs and sand in the reaction system. Interaction force measurements indicated that SRHA inhibits the approach of the TiO2 NPs to the sand surface, as expected by the Derjaguin–Landau–Verwey–Overbeek calculation. However, the adhesion force of TiO2 NPs to sand was not critically affected by the presence of SRHA. TiO2 NP sorption to natural sand was limited as to the acid-treated sand in the presence of SRHA, implying that the organics dissolved from natural sand might facilitate the transport of TiO2 NPs in aquifers by inhibiting TiO2 NP sorption to aquifer materials.

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.

This paper provides a comparison of high power semiconductor devices in 5MW-class Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) wind turbines. High power semiconductor devices of press-pack type IGCT, module type IGBT, press-pack type IEGT, and press-pack type IGBT of both 4.5kV and 6.5kV are considered in this paper. Benchmarking is performed based on neutral point clamped 3-level back-to-back type voltage source converter supplied from grid voltage of 4160V. The feasible number of semiconductor devices in parallel is designed through the loss analysis considering both conduction and switching losses under the given operating conditions of 5MW-class PMSG wind turbines, particularly for the application in offshore wind farms. The loss analysis is confirmed through PLECS simulations. The comparison result shows that press-pack IGCT type semiconductor device has the highest efficiency.

Previously identified relationships between the attachment efficiency ( α ) and seepage velocity ( U S ) of nanoparticles (NPs) were tested under simulated subsurface transport conditions, where the value of U S is typically much less than the U S on which they are based. This found an increase in the α value of TiO 2 NPs with respect to U S , which contradicts previous reports suggesting a constant value or decrease. By comparing the adhesion energy of the TiO 2 NPs to sand and the hydrodynamic energy required to detach them, the increase of α with respect to U S is found to be due to the difference in the magnitude of U S considered; with 6.1E−05 to 1.3E−03 m s −1 used in previous studies, whereas the current study uses a value in the range from 2.4E−06 to 4.9E−04 m s −1 . Only one of the previous models predicting α showed a similar increase of α with U S , which was the result of it employing low velocities to examine the effects of organic matter. The current findings therefore suggest that previously determined relationships between α and U S need to be further developed to incorporate more variables before they can be effectively used to describe or predict the subsurface transport of TiO 2 NPs.

This paper provides a comparison of high power semiconductor devices in 5MW-class Permanent Magnet Synchronous Generator (PMSG) Medium Voltage (MV) wind turbines. High power semiconductor devices of IGCT, module type IGBT, press-pack type IGBT, and press-pack type IEGT of both 4.5kV and 6.5kV are considered in this paper. Benchmarking is performed based on neutral point clamped 3-level back-to-back type voltage source converter supplied from grid voltage of 4160V. The feasible number of semiconductor devices in parallel is designed through the loss analysis considering both conduction and switching losses under the given operating conditions of 5MW-class PMSG wind turbines, particularly for the application in offshore wind farms. The loss analysis is confirmed through PLECS simulations. The comparison result shows that press-pack type IGBT and IGCT semiconductor device have the highest efficiency considering the snubber loss of IGCT.

Neutron reflectometry (NR) was employed to study the interaction of nanosized silica particles with a flat silica surface in aqueous solutions. Unlike other experimental tools that are used to study surface interactions, NR can provide information on the particle density profile in the solution near the interface. Two types of silica particles (25 and 100 nm) were suspended in aqueous solutions of varying ionic strength. Theoretical calculations of the surface interaction potential between a particle and a flat silica surface using the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory were compared to the experimental data. The theory predicts that the potential energy is highly dependent on the ionic strength. In high ionic strength solutions, NR reveals a high concentration of particles near the flat silica surface. Under the same conditions, theoretical calculations show an attractive force between a particle and a flat surface. For low ionic strength solutions, the particle concentration near the surface obtained from NR is the same as the bulk concentration, while depletion of particles near the surface is expected because of the repulsion predicted by the DLVO theory.

This paper presents a simple and cost-effective stand-alone rapid battery charging system of 30kW for electric vehicles. The proposed system mainly consists of active front-end rectifier of neutral point clamped 3-level type and non-isolated bi-directional dc-dc converter of multiphase interleaved half-bridge topology. The charging system is designed to operate for both lithium-polymer and lithium-ion batteries. The complete charging sequence is made up of three sub-interval operating modes; pre-charge mode, constant-current mode, and constant-voltage mode. The pre-charge mode employs the stair-case shaped current profile to accomplish shorter charging time while maintaining the reliable operation of the battery. The proposed system is able to reach the full-charge state within less than 16min for the battery capacity of 8kWh by supplying the charging current of 78A. The optimal discharging algorithm for Vehicle to the Grid (V2G) operation has been adopted to maintain the discharging current of 1C. Owing to the simple and compact power conversion scheme, the proposed solution has superior module-friendly mechanical structure which is absolutely required to realize flexible power expansion capability in a very high-current rapid charging system.

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

Soft phase magnetic Fe-B nanoparticles were prepared by coprecipitation and the hard phase magnetic Nd-Fe-B nanoparticles were obtained from mechanical ball mill of the bulk Nd-Fe-B with a shaker mill. Also mechanical ball mill technique was applied to the mixture of Nd-Fe-B and Fe-B nanoparticles to build up an exchange-coupled nanocomposite magnet. It was loaded in electronic furnace and annealed under a flow of hydrogen at 953 K for 30 min. The exchange coupled interaction of isotropic magnets was characterized by smooth hysteresis loop with a high value of remanence (Mr/Ms > 0.5).

High temperature solution phase decomposition of Fe(CO)5 and reduction of Pt(acac)2 in the presence of stabilizers of oleic acid and oleyl amine are employed to produce Fe1–xPtx alloy nanoparticles. The Fe and Pt composition of the nanosized materials can be tuned by adjusting the molar ratio of Fe(CO)5 to Pt(acac)2, and the compositions ranging from Fe40Pt60 to Fe80Pt20 are obtained. This study is to investigate the influence of the composition on Curie temperature (Tc) of Fe1–xPtx nanoparticles monitored by thermomagnetic analysis (TMA).