Winding Modes Research Articles

Characterization of the biofouling and cleaning efficiency of nanofiltration membranes

The nanofiltration (NF) drinking water production unit of the Méry-sur-Oise plant (Val d'Oise, France) consists of eight identical filtration trains composed of three stages positioned in steps for a production capacity of 140,000 m3 day−1. To gain a better understanding of the irreversible fouling of the NF membranes, spiral wound modules in operation for 8 years from each of the three stages of the plant were autopsied before and after chemical cleaning and analysis by Attenuated Total Reflection Fourier Transform Infrared spectroscopy, Inductive Coupled Plasma-Atomic Emission Spectrometry, contact angles, adenosine triphosphate (ATP) content measurements, and rheometry. The fouled membranes from the three stages had similar contact angles of approximately 60°. Relative infrared signals typical of biofilms were classified in descending order from stage 1 to stage 3. The foulant matter of stages 1 and 2 contained similar but weaker ATP concentrations than stage 3. During rheometry experiments, rotation and oscillation analyses demonstrated that the biofilm of stage 3 was less viscous and less elastic than the biofilms of stages 1 and 2. After cleaning, all the parameters analyzed demonstrated a quantitative decrease in the fouling matter at the NF membrane surface, but a biofilm with intact viscoelastic properties (unchanged G′ and G″ values) remained at the membrane surface for the three stages. The persistence of biofilm material with intact mechanical properties at the NF membrane surface after chemical cleaning may result in permanent permeability decreases.

A loop of SU(2) gauge fields stable under the Yang-Mills flow

The gradient flow of the Yang-Mills action acts pointwise on closed loops of gauge fields. We construct a topologically nontrivial loop of SU(2) gauge fields on S that is locally stable under the flow. The stable loop is written explicitly as a path between two gauge fields equivalent under a topologically nontrivial SU(2) gauge transformation. Local stability is demonstrated by calculating the flow equations to leading order in perturbations of the loop. The stable loop might play a role in physics as a classical winding mode of the lambda model, a 2-d quantum field theory that was proposed as a mechanism for generating spacetime quantum field theory. We also present evidence for 2-manifolds of SU(3) and SU(2) gauge fields that are stable under the Yang-Mills flow. These might provide 2-d instanton corrections in the lambda model. For Isidore M. Singer in celebration of his eighty-fifth birthday.

Quantifying the Eddy Feedback and the Persistence of the Zonal Index in an Idealized Atmospheric Model

Abstract An idealized atmospheric model is employed to quantify the strength of the eddy feedback and the persistence of the zonal index. The strength of the surface frictional damping on the zonal index is varied, and an external zonal momentum forcing is included to compensate for the momentum change associated with the friction change such that the climatological jet latitude and shape are unchanged. The model can generate a nearly identical climatology and leading mode of the zonal mean zonal wind for different frictional damping rates, except when the jet undergoes a regime transition. For those experiments without a regime transition, as the surface friction is increased, the strength of eddy feedback is enhanced but the zonal index becomes less persistent. A simple feedback model suggests that the e-folding decorrelation time scale of the zonal index can be determined by the frictional damping rate and the strength of eddy feedback. The strength of eddy feedback is found to be related to the instantaneous vertical wind shears near the surface controlled by the frictional damping. Furthermore, the climate response to an external zonal torque is proportional to the decorrelation time scale, although the simple prediction used here overestimates the climate response by a factor of 2.

Effect of draw solution concentration and operating conditions on forward osmosis and pressure retarded osmosis performance in a spiral wound module

Forward osmosis (FO) and pressure retarded osmosis (PRO) are concentration-driven membrane processes. While they can be potentially used in water, wastewater, and energy applications, these processes suffer from the concentration polarization inside the porous membrane support resulting in severe flux decrease, a phenomenon known as internal concentration polarization (ICP). Researchers have investigated the effect of ICP both in theoretical and experimental studies. The current study extends the existing ICP model to include the effect of draw solution dilution by membrane permeate flow in a spiral wound FO module (SWFO). FO and PRO experiments were performed using a Hydrowell ® SWFO under both submerged and cross-flow conditions. The effect of draw solution concentration, draw solution flow rate, feed water flow rate, and membrane orientation on FO and PRO water flux performance was systematically investigated. Permeate flow increased with greater draw solution concentration in both FO and PRO modes. ICP was found to drastically limit the available membrane flux in the concentration-driven membrane processes, and its adverse effect was more severe at greater draw solution concentration. Membrane flux was also affected by the dilution of draw solution when the permeate flow rate was comparable or greater than the draw solution flow rate. The submerged FO configuration performed nearly as good as the cross-flow configuration with feed water circulating outside of the membrane envelope (shorter flow path). In this case, the feed water flow rate only had limited effect on membrane flux likely due to its low mass transfer resistance. In contrary, the membrane flux can be adversely affected at low feed water flow rate when it was circulated inside of the membrane envelope (longer flow path).

Properties of the average distribution of equatorial Kelvin waves investigated with the GROGRAT ray tracer

Abstract. Kelvin waves excited by tropospheric convection are considered to be one of the main drivers of the stratospheric quasi-biennial oscillation (QBO). In this paper we combine several measured data sets with the Gravity wave Regional Or Global RAy Tracer (GROGRAT) in order to study the forcing and vertical propagation of Kelvin waves. Launch distributions for the ray tracer at tropospheric altitudes are deduced from space-time spectra of European Centre for Medium-Range Weather Forecasts (ECMWF) operational analyses, as well as outgoing longwave radiation (OLR) and rainfall data measured by the Tropical Rainfall Measuring Mission (TRMM) satellite. The resulting stratospheric Kelvin wave spectra are compared to ECMWF operational analyses and temperature measurements of the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) satellite instrument. Questions addressed are: the relative importance of source variability versus wind modulation, the relative importance of radiative and turbulent damping versus wave breaking, and the minimum altitude where freely propagating waves dominate the spectrum.

QBO effects on Antarctic mesospheric winds and polar vortex dynamics

A dynamical link is demonstrated between the equatorial quasi‐biennial oscillation (QBO) and high‐latitude mesospheric zonal winds recorded by an Imaging Doppler Interferometer (IDI) at Halley, Antarctica. Above ∼80 km eastward winds in winter (an extension of the polar vortex into the mesosphere) are strengthened under easterly 50 hPa QBO conditions. This is similar to the Holton‐Tan effect in the stratosphere but working in opposition. The weak winter time zonal winds are shown to differ by up to 2.6 m/s dependent on QBO phase. In spring, zonal winds are most strongly correlated with the equatorial 25 hPa QBO and are significantly more westerly in November, an extension of the QBO response in the stratosphere below. It is suggested that QBO modulation of the vortex winds in the Antarctic mesosphere is dependent on planetary‐wave activity from the Antarctic in winter and Arctic in spring.

PERFORMANCE PREDICTION OF MEMBRANE MODULES INCORPORATING THE EFFECTS OF SUCTION IN THE MASS TRANSFER COEFFICIENT UNDER LAMINAR AND TURBULENT FLOW CONDITIONS FOR NON‐NEWTONIAN FLUIDS

ABSTRACT Design equations for spiral wound membrane modules in case of power law fluid are derived for the first time. The case is solved for both laminar and turbulent flow regimes considering orange juice as the model system. The governing equations are solved numerically and the profiles of transmembrane pressure drop, bulk velocity, concentration, permeate flux, membrane surface concentration and permeate concentration along the membrane module are obtained. A detailed parametric study is carried out to observe the effects of operating conditions on the permeate flux and permeate concentration. The present analysis is helpful to design and simulate the performance of the membrane modules adequately. For the model system, it is observed that the axial pressure drop is about 2 to 3% of the inlet transmembrane pressure drop for 1.0 m length of the module. The mass transfer coefficient increases by twofold when the flow regime becomes turbulent. In case of laminar flow, at 7,000‐kPa inlet transmembrane pressure drop, the average flux is about 22 L/m2·h and the flux value under turbulent flow condition becomes about 30 L/m2·h at the same pressure drop. For a slightly leaky membrane, at 7,000‐kPa pressure drop and 130 kg/m3 of feed soluble sugar concentration, the permeate stream contains about 10 kg/m3 of total sugar. PRACTICAL APPLICATIONThe application of membrane technology is one of the emerging areas in food industry. The major application includes fruit juice clarification and concentration. Therefore, appropriate design of membrane modules is of utmost importance. Most of the fruit juices are non‐Newtonian in nature and they obey, in general, power law rheology. The derivation of detailed design equations of a spiral wound module is carried out considering a power law fluid, both under laminar and turbulent flow regimes. The presented method provides a way to design the membrane modules in great detail (i.e., incorporating effects of suction in mass transfer coefficient, developing concentration boundary layer, non‐Newtonian fluid, etc.). This will be helpful to design a spiral wound module to meet a target productivity (i.e., permeate flux) and permeate quality (i.e., permeate concentration).

Gauge threshold corrections for local orientifolds

We study gauge threshold corrections for systems of fractional branes at local orientifold singularities and compare with the general Kaplunovsky-Louis expression for locally supersymmetric = 1 gauge theories. We focus on branes at orientifolds of the 3/4, 3/6 and 3/6' singularities. We provide a CFT construction of these theories and compute the threshold corrections. Gauge coupling running undergoes two phases: one phase running from the bulk winding scale to the string scale, and a second phase running from the string scale to the infrared. The first phase is associated to the contribution of = 2 sectors to the IR β functions and the second phase to the contribution of both = 1 and = 2 sectors. In contrast, naive application of the Kaplunovsky-Louis formula gives single running from the bulk winding mode scale. The discrepancy is resolved through 1-loop non-universality of the holomorphic gauge couplings at the singularity, induced by a 1-loop redefinition of the twisted blow-up moduli which couple differently to different gauge nodes. We also study the physics of anomalous and non-anomalous U(1)s and give a CFT description of how masses for non-anomalous U(1)s depend on the global properties of cycles.

Application and optimization in chromium-contaminated wastewater treatment of the reverse osmosis technology

Chromium (Cr) is the most important element used to plate other metals and electroplating factories are still considered to be the most important industries which pollute the environment to this metal. This paper describes a study conducted to determine the efficiency of reverse-osmosis (RO) as a membrane technique for removal of Cr from wastewater samples synthetically prepared to be similar to electroplating effluents. Methods: The RO unit used in this study was a spiral wound module of 2521 TE made by a Korean CSM company. Syn- thetic wastewater samples containing Cr ions at various concentrations of 1 to 20 mg/L were prepared and subjected to treatment by RO, and quantitative analysis had been accomplished by a colorimetric method. Evaluation of optimized conditions of treatment had also been carried out by determining the effects of changing operating pressure, temperature and pHS of samples. Results: Optimum conditions of Cr-treatment by RO in 10 g/L initial Cr concentration were determined to be in the pH range of 6 to 7 and in temperature of about 25oC at an applied pressure of 200 psi. Conclusion: Considering the efficiency of Cr removal which was as high as 99% at the optimized conditions it could be concluded that RO membrane process may be selected and developed as an effective alternative for treatment of metal- contaminated effluents of electroplating and similar industries.

Design, Development, and Field Testing of Sixteen Inch Diameter RO Modules in a Waste Water Reuse Application

Large diameter spiral wound modules enable significant reductions in reverse osmosis (RO) plant cost. A consortium of membrane manufacturers had identified sixteen inches as the optimum diameter for a new standard. In order to make full use of the cost saving potential of the large diameter, FilmTec's design considerations were based on a scale-up from the proven design of commercially available 8-inch modules. With the same materials and a leaf design as in 8-inch modules, the new 16-inch modules were built with a 4.3 times higher active membrane area and accordingly a 4.3 times higher permeate flow performance. The product water tube was designed for increased physical strength at even less permeate pressure drop. The endcaps feature interlocking technology without interconnectors and with internal brine seals for easier loading. The fiberglass shell was reinforced to resist axial compression arising from pressure drop and increased cross-section area. Sufficient safety margins were verified through extensive testing. A prototype tool for easy element loading and unloading was developed and applied to the demonstration plant at Bedok in Singapore. This plant is in operation since October 2007 to demonstrate equivalent performance of an 8-inch and a 16-inch RO system running side-by-side on a challenging waste water reuse application. Each system has three 7-element pressure vessels in a 2:1 arrangement and was operated at a constant flux of 17.3 lmh and a recovery of 75%. After some adjustments of the scaling inhibitor dosage the plant had come to a stable operation; at the time of this writing it was approaching 3 months without cleaning or rinsing. The normalized permeate flow of the 16-inch system was 4.3 times higher than the flow of the 8-inch system. A sustainable system flow performance at a fouling factor of 0.85 was demonstrated. The measured system salt rejection indicated an average module salt rejection of 99.65%.

Winding effects on brane/anti-brane pairs

We study a brane/anti-brane configuration which is separated along a compact direction by constructing a tachyon effective action which takes into account transverse scalars. Such an action is relevant in the study of HQCD model of Sakai and Sugimoto of chiral symmetry breaking, where the size of the compact circle sets the confinement scale. Our approach is motivated by string theory orbifold constructions and gives a route to model inhomogeneous tachyon decay. We illustrate the techniques involved with a relatively simple example of a harmonic oscillator on a circle. We will then repeat the analysis for the Sakai-Sugimoto model and show that by integrating out the winding modes will provide us with a renormalized action with a lower energy than that of truncating to zero winding sector.

The Use of MTM-SVD Technique to Explore the Joint Spatiotemporal Modes of Wind and Sea Surface Variability in the North Indian Ocean during 1993–2005

Sea surface height (SSH) and sea surface temperature (SST) in the North Indian Ocean are affected predominantly by the seasonally reversing monsoons and in turn feed back on monsoon variability. In this study, a set of data generated from a data-assimilative ocean model is used to examine coherent spatiotemporal modes of variability of winds and surface parameters using a frequency domain technique, Multiple Taper Method with Singular Value Decomposition (MTM-SVD). The analysis shows significant variability at annual and semiannual frequencies in these fields individually and jointly. The joint variability of winds and SSH is significant at interannual (2-3 years) timescale related to the ENSO mode—with a “/dipole/” like spatial pattern. Joint variability with SST showed similar but somewhat weaker behavior. Winds appear to be the driver of variability in both SSH and SST at these frequency bands. This offers prospects for long-lead projections of the North Indian Ocean climate.

Satellite Observations on Cyclone-Induced Upper Ocean Cooling and Modulation of Surface Winds—A Study on Tropical Ocean Region

In this letter, we evaluate the relationships between the sea-surface temperatures (SSTs) and meteorological parameters over the Bay of Bengal region, India, using microwave satellite remote sensing data. Most of the cyclones in this region occur during the premonsoon period in April-June and are associated with SSTs greater than 26degC. We particularly analyzed the data from two recent cyclonic events: Mala that occurred in April 24, 2006 and Tropical Cyclone 01B (TC 01B) that occurred in May 11, 2003. We used two different remote sensing data sets, sea surface temperature (SST) from the Tropical Rainfall Measurement Mission and the NASA QuikSCAT ocean surface wind vectors to characterize the ocean-atmosphere interactions in cold SST regions formed in the trail of the aforementioned two cyclone events. The results from the satellite data analysis suggested the systematic weakening of wind speed over the cold patch, along the trail of the cyclone. A cooling of around 4deg-5deg was observed to be associated with the passage of cyclone Mala. Wind speed gradually increased from 2 to 9 m/s from the center to the boundary of the cold patch and showed good correlation with SST (r = 0.97). These observations have been validated with another cyclone data (TC 01B) over the Bay of Bengal region that occurred during May 2003. Our results were consistent with the Wallace hypothesis that SST modulates the surface winds via stability.

Impacts of the Madden–Julian Oscillation on Australian Rainfall and Circulation

Abstract Impacts of the Madden–Julian oscillation (MJO) on Australian rainfall and circulation are examined during all four seasons. The authors examine circulation anomalies and a number of different rainfall metrics, each composited contemporaneously for eight MJO phases derived from the real-time multivariate MJO index. Multiple rainfall metrics are examined to allow for greater relevance of the information for applications. The greatest rainfall impact of the MJO occurs in northern Australia in (austral) summer, although in every season rainfall impacts of various magnitude are found in most locations, associated with corresponding circulation anomalies. In northern Australia in all seasons except winter, the rainfall impact is explained by the direct influence of the MJO’s tropical convective anomalies, while in winter a weaker and more localized signal in northern Australia appears to result from the modulation of the trade winds as they impinge upon the eastern coasts, especially in the northeast. In extratropical Australia, on the other hand, the occurrence of enhanced (suppressed) rainfall appears to result from induced upward (downward) motion within remotely forced extratropical lows (highs), and from anomalous low-level northerly (southerly) winds that transport moisture from the tropics. Induction of extratropical rainfall anomalies by remotely forced lows and highs appears to operate mostly in winter, whereas anomalous meridional moisture transport appears to operate mainly in the summer, autumn, and to some extent in the spring.

Effect of storage of NF membranes on fouling deposits and cleaning efficiency

The aim of this work was to investigate changes of the foulant deposit during storage and the impact of storage onto cleaning efficiency of a nanofiltration membrane. ATR-FTIR analysis and chemical cleaning tests were performed on membrane pieces cut from a NF spiral wound module extracted from a drinking water plant just after sampling or stored for 4 or 8 weeks in distilled water at 4°C. Membrane permeability of flat sheets was measured before and after cleaning with a cross flow lab-scale pilot. For the non stored membrane, an homogeneous biofouling deposit was observed on the membrane surface by ATR-FTIR analysis. During membrane storage, some heterogeneity between the spectra, corresponding to different areas of the membrane appeared. A decrease of IR signals of foulants was observed after the first 4 weeks of storage; thereafter the IR signals remained approximately the same. The membrane permeability of the fouled flat sheets increased slightly after 4 weeks and remained stable after 8 weeks of storage. After cleaning, the biofilm IR signals of the membrane samples analyzed immediately after sampling or stored for 4 weeks decreased significantly. Cleaning had no significant effects on the biofoulant deposit after a storage of 8 weeks. Increases in permeability of 10, 5, and 5% were obtained after cleaning of the fouled flat sheets not stored, stored for 4 or 8 weeks, respectively. In conclusion, the storage of fouled NF membrane cuts in distilled water at 4°C conducted to alterations of the biofouling deposit but was compatible with cleaning efficiency tests after a storage period of 4 weeks at the most.

Toluene recovery from simulated gas effluent using POMS membrane separation technique

Membrane with polyoctylmethyl siloxane (POMS) separation layer, in flat and spiral wound module, was tested to remove toluene from air by applying vacuum pressure at the permeate side of the membrane. Effect of vacuum pressure (0.02–0.1 MPa), feed flow rate (0.6–3.0 × 10 −2 m 3/h, linear velocity across the membrane at 4.3–21.5 m 3/(m 2 h)) and toluene concentration (1500–4000 mg/m 3, common for industrial effluents) on removal efficiency of the flat membrane module was determined. Under similar feed concentration and vacuum pressure, a higher toluene removal efficiency was obtained using the spiral wound membrane module than using the flat membrane, when flow rates in spiral wound unit ranged 0.15–0.27 m 3/h (linear velocities across the membrane at 2.0–3.15 m 3/(m 2 h), much lower than in flat membrane). Under 0.09 MPa vacuum, toluene removal in spiral wound unit ranged between 70 and 84%. The removal percentage of toluene did not change much when its concentration increased in feed. This result shows that the membrane used to recover toluene in effluent stream can achieve high removal efficiency.

Contact interactions in low scale string models with intersectingD6-branes

We evaluate the tree level four fermion string amplitudes in the TeV string mass scale models with intersecting $D6$-branes. The coefficient functions of contact interactions subsuming the contributions of string Regge resonance and winding mode excitations are obtained by subtracting out the contributions from the string massless and massive momentum modes. Numerical applications are developed for the standard-model-like solution of Cremades, Ibanez, and Marchesano for a toroidal orientifold with four intersecting $D6$-brane stacks. The chirality conserving contact interactions of the quarks and leptons are considered in applications to high-energy collider and flavor changing neutral current phenomenology. The two main free parameters consist of the string and compactification mass scales, ${m}_{s}$ and ${M}_{c}$. Useful constraints on these parameters are derived from predictions for the Bhabha scattering differential cross section and for the observables associated to the mass shifts of the neutral meson systems $K\ensuremath{-}\overline{K}$, $B\ensuremath{-}\overline{B}$, $D\ensuremath{-}\overline{D}$ and the lepton number violating three-body leptonic decays of the charged leptons $\ensuremath{\mu}$ and $\ensuremath{\tau}$.

Components of precipitation and temperature anomalies and change associated with modes of the Southern Hemisphere

AbstractA long simulation of climate by the CSIRO Mark 3 coupled atmosphere—ocean model is analysed to assess the role of three modes of the Southern Hemisphere (SH) circulation on the inter‐annual variability of precipitation and surface temperature and the contribution of the modes to patterns of change under global warming. Indices of El Niño‐southern oscillation (ENSO) and the high‐ and low‐latitude modes (HLM, LLM) of zonal mean zonal wind are extracted from monthly means during the period 1871–1970. The model El Niño brings mostly drier and warmer conditions to Australia—New Zealand (NZ), South America and southern Africa in both annual and seasonal means. The HLM and LLM modes impact rainfall and temperature in banded patterns. Positive HLM [which is closely related to the southern annular mode (SAM) in pressure] moistens and cools around 20–35°S particularly near the east coast of each continent. Farther south it mostly dries and warms, especially in the austral winter. The LLM has some impacts, including increased summer rain in western Australia, and temperature anomalies in eastern South America in autumn. Mostly similar patterns are found in the ERA40 observational data. Changes in the indices in the 22nd century, following warming forced by the A1B greenhouse gas (GHG) scenario, are positive, in most cases, and similar in magnitude to their inter‐annual variability. The drying and warming of Australia associated with an El Niño‐like change are largely countered by the HLM‐like change, and similar effects are seen in parts of the other continents. The far south of NZ and South America are dried and warmed by the HLM change, but these relative changes are countered by non‐modal effects in the Southern Ocean. Overall the impact of the simulated modes is largest on Australia, with the HLM being as important as ENSO in the mid‐latitudes. Copyright © 2008 Royal Meteorological Society

Partial Hydrogenation of Soybean Oil with Minimal Trans Fat Production Using a Pt‐Decorated Polymeric Membrane Reactor

AbstractPartial hydrogenation of vegetable oils is carried out to improve the chemical stability and raise the melting point to produce semi‐solid products such as margarine. Trans fatty acids formed during traditional hydrogenation have come under intense scrutiny with regard to human health. Here we report partial hydrogenation of soybean oil using a high performance integral‐asymmetric polyetherimide membrane sputtered with platinum to deliver hydrogen directly to or near the catalytic sites. Oil flows past the platinum‐coated “skin” side of the membrane while dissolved molecular and some atomic hydrogen is supplied from the highly porous substructure of the membrane. The membrane has a high hydrogen flux but is essentially impermeable to soybean oil. Hydrogenation using our metal/polymer catalytic composite membrane produced oil with only 4 wt.% total trans fatty acids and 14.5 wt.% C18:0 saturates at IV of 95 while the conventional Pt/C slurry reactor produced more than 10 wt.% TFA and the same amount of C18:0 saturates under similar conditions of temperature and pressure. Our concept requires hydrogen pressures of only about 65 psi and temperatures near 70 °C. The polymeric base membranes used here have been mass produced and can be packaged in spiral wound modules. The relatively mild reaction conditions and the direct pathway to produce useful membrane modules combine to make our concept promising for near‐term application.

High-Order Sliding Control for a Wind Energy Conversion System Based on a Permanent Magnet Synchronous Generator

This paper presents the output power control of a wind energy conversion system (WECS) based on a permanent magnet synchronous generator (PMSG). It is assumed that the considered wind module integrates a stand-alone hybrid generation system, jointly with a battery bank, a variable ac load, and other generation subsystems. The operation strategy of the hybrid system determines two possible operation modes for the WECS, depending on the power requirements of the load and the wind availability. The paper deals with the design of a combined high-order sliding mode (HOSM) controller for the power control of the WECS on both operational modes. The main features of the obtained controller are its chattering-free behavior, its finite-time reaching phase, its simplicity, and its robustness with respect to external disturbances and unmodeled dynamics. The performance of the closed-loop system is assessed through representative computer simulations.