A modeling approach to ameliorate the energetic efficiency of reverses osmosis membrane for salt water desalination

Electromagnetic Environment Associated with Lightning Strikes to Tall Strike Objects

Magnetic and electric field variations during geomagnetically active days over Turkey

Bioinspired humic acid-based membranes for water desalination: Mechanistic insights from molecular simulations

Membranes are widely used in industrial separation processes, particularly for gas separation and desalination processes. To develop membrane materials with improved permeability, selectivity can achieve more energy-efficient membrane separations and reduce costs. Since composite membranes offer improved performance, the aim of this research is to develop polymer-based composite membranes with improved performance for gas separation and water desalination applications. First, in order to obtain a composite membranes with high chlorine tolerance, a carbonaceous poly(furfuryl alcohol) (PFA) composite membrane was synthesized at a low temperature carbonation by formation and post-treatment of a thin PFA layer on porous polymer substrates. The carbonaceous PFA membrane exhibits high selectivity and excellent chemical stability in seawater desalination. The low-temperature carbonization method developed in this study is promising for developing a wide range of other carbonaceous polymer composite membranes for water desalination. Next, in order to apply PFA to other applications, understanding the effects of polymerization conditions on the properties of the PFA composite membrane is required. The PFA membrane was fully characterized in terms of microstructure and separation properties. Suitable synthesis conditions for the preparation of PFA composite membranes with smooth surfaces and uniform structure were (1) FA/ H2SO4 molar ratios: 74-300, (2) polymerization temperatures: 80-100°C and (3) solvents: ethanol and acetone. The preparation conditions were also optimized. The PFA composite membrane prepared with a FA/ H2SO4 molar ratio of 250, a polymerization temperature of 80°C and with ethanol as the solvent exhibited the highest H2/N2 ideal selectivity (αH2/N2=24.9), and a H2 permeability of 206 Barrers. This work led to a better understanding of the effect of the preparation procedures on the membrane performance. In order to investigate the effects of the incorporation of molecular sieve nanoparticles on the membrane structure and membrane performance, silicalite-poly(furfuryl alcohol) (PFA) mixed matrix composite membranes were successfully synthesized based on the best synthesis condition obtained previously. The silicalite-PFA mixed matrix composite membrane with 20% w/w silicalite loading had a high ideal selectivity (αo2/N2= 3.5 and αco2/N2= 5.4) and a good permeability (Po2= 821.2, Pco2= 1263.7, PN2= 233.3 Barrers) at room temperature. This membrane can be a good candidate for oxygen enrichment applications. Finally, in order to investigate the effects of the incorporation of silicalite nanocrystals on the desalination property of polyamide membranes, silicalite nanocrystals were also incorporated into polyamide matrix to synthesize silicalite-polyamide mixed matrix membranes. With an increase in the loading of silicalite nanocrystals, the water flux of silicalite-polyamide mixed matrix composite membranes increased whereas the salt selectivity significantly decreased. The silicalite-polyamide mixed matrix composite membrane prepared from TMC-hexane with 0.5% (w/v) silicalite had water flux of 2.7×10-6 m3/m2·s and NaCl rejection of 50% at a feed pressure of 34.5 bar which 2000 ppm salt solution was used as the feed. The silicalite-polyamide mixed matrix composite membrane is promising for developing high water flux composite membranes for water desalination. In this research, composite membranes with improved permeability, selectivity and chemical resistance were successfully synthesized for desalination and gas separation. For desalination, carbonaceous PFA composite membranes with high chlorine tolerance and silicalite-PA mixed matrix composite membranes with high salt rejection and water flux were successfully obtained. For gas separation, an optimized composite membranes PFA synthesis condition was found and silicalite-PFA mixed matrix composite membranes with high O2/N2 separation were successfully synthesized.

Mechanical properties of water desalination and wastewater treatment membranes

Phase difference between electric and magnetic fields of the electromagnetic waves

SUMMARY Studied in this paper are the properties of seismoelectromagnetic waves radiated by a double couple in a saturated porous medium arising from the electrokinetic effect. First, using the Pride's equations, we derive the Green's function of the magnetic field due to a single point force as a complement of previous authors’ works, in which only the Green's functions of the solid displacement, the relative fluid–solid displacement and the electric field were expressed. Furthermore, we extend these Green's functions to cater for the moment tensor sources. Then we derive the Green's functions of the solid displacement, the electric and magnetic fields in the frequency-space domain excited by a double couple source, which is frequently used in earthquake seismology. To visualize these fields, the radiation patterns are calculated and displayed. The results illustrate that the radiation pattern of the electric far field for the longitudinal (or transverse) wave is the same in shape as that of the far field of the P (or S) wave in elastodynamics. For a transverse wave, the electric and magnetic far fields share the same radiation patterns in shape, while the electric and magnetic near fields do not. For each of the four body waves, the far, intermediate and near fields are compared at different receiver-to-source distances, respectively. The electromagnetic (EM) wave has a much longer near-field-dominating distance than the seismic waves. We calculate the waveforms in the time–space domain by numerically Fourier transforming the Green's functions into the time domain. In order to validate these Green's functions and the waveforms, we calculate the waveforms again by another method. The main idea of the method is regarding the source as a displacement–stress–EM discontinuity vector. The result shows that the waveforms from those two methods are in excellent agreement. In the waveforms, there are the electric fields accompanying both the P and S waves, as well as the magnetic field accompanying the S wave. We testify that the S wave generally has a weaker capacity than the P wave in inducing an electric field. In the waveforms, there is also an independently propagating EM wave, which has a much higher speed than the seismic waves, and reaches the observation point immediately after the source launched. By comparing the waveforms at different receiving locations, we find that waveforms differ at different observation orientations.

Recent laboratory and epidemiological results have stimulated interest in the hypothesis that human beings may exhibit biological responses to magnetic and/or electric field transients with frequencies in the range between 100 Hz and 100 kHz. Much can be learned about the response of a system to a transient stimulation by understanding its response to sinusoidal disturbances over the entire frequency range of interest. Thus, the main effort of this paper was to compare the strengths of the electric fields induced in homogeneous ellipsoidal models by uniform 100 Hz through 100 kHz electric and magnetic fields. Over this frequency range, external electric fields of about 25–2000 V/m (depending primarily on the orientation of the body relative to the field) are required to induce electric fields inside models of adults and children that are similar in strength to those induced by an external 1 μT magnetic field. Additional analysis indicates that electric fields induced by uniform external electric and magnetic fields and by the nonuniform electric and magnetic fields produced by idealized point sources will not differ by more than a factor of two until the sources are brought close to the body. Published data on electric and magnetic field transients in residential environments indicate that, for most field orientations, the magnetic component will induce stronger electric fields inside adults and children than the electric component. This conclusion is also true for the currents induced in humans by typical levels of 60 Hz electric and magnetic fields in U.S. residences. Bioelectromagnetics 18:67–76, 1997. © 1997 Wiley-Liss, Inc.

Recent laboratory and epidemiological results have stimulated interest in the hypothesis that human beings may exhibit biological responses to magnetic and/or electric field transients with frequencies in the range between 100 Hz and 100 kHz. Much can be learned about the response of a system to a transient stimulation by understanding its response to sinusoidal disturbances over the entire frequency range of interest. Thus, the main effort of this paper was to compare the strengths of the electric fields induced in homogeneous ellipsoidal models by uniform 100 Hz through 100 kHz electric and magnetic fields. Over this frequency range, external electric fields of about 25-2000 V/m (depending primarily on the orientation of the body relative to the field) are required to induce electric fields inside models of adults and children that are similar in strength to those induced by an external 1 microT magnetic field. Additional analysis indicates that electric fields induced by uniform external electric and magnetic fields and by the nonuniform electric and magnetic fields produced by idealized point sources will not differ by more than a factor of two until the sources are brought close to the body. Published data on electric and magnetic field transients in residential environments indicate that, for most field orientations, the magnetic component will induce stronger electric fields inside adults and children than the electric component. This conclusion is also true for the currents induced in humans by typical levels of 60 Hz electric and magnetic fields in U.S. residences.

In-plane omnidirectional magnetic field sensor based on Giant Magneto Impedance (GMI)

In two-valley semiconductors of the GaAs type, under the influence of external electric E0 and magnetic fields H0 at certain orientations and , a current oscillation with a specific frequency and growth rate was obtained. The orientation of the electric E0 and magnetic fields H0 plays a significant role in the excitation of growing waves in semiconductors of the GaAs type. The frequencies and growth increments are determined when exciting current oscillations in a circuit. The dimensions of the crystal are determined by Lz >> Lx, Ly, Lx = Ly. If the dimensions of the sample differ from the condition Lz >> Lx, Ly, Lx = Ly, the growing waves can fade or grow. And in this case, the frequencies of the oscillation growth and the value of the electric E0 and magnetic H0 fields will be different. The values of the magnetic field in the valley “a” are strong, i.e. μaH0 >> c, and in the valley “b” are weak μbH0 >> c. If the magnetic field values in the valleys “a” and “b” are strong, then electromagnetic waves with other frequencies will also be excited. The theory for other values of the magnetic, electric field and, of course, for other values of the crystal dimensions will show other values for the frequency and growth increment. When preparing semiconductor devices (generators, amplifiers, etc.), the dimensions of the sample play a significant role. In this work, analytical expressions for the electric and magnetic fields for certain sample sizes Lx, Ly, Lz were obtained.

Aim: To assess the influences of imaging variation (different photographic angle) on the measurement of retinal vascular fractal dimension (Df), using two segmentation methods.Materials and methods: Nonlinear orthogonal projection segmentation (International Retinal Imaging Software-Fractal, termed IRIS-Fractal) and curvature-based segmentation (Singapore Institute Vessel Assessment-Fractal, termed SIVA-Fractal) methods were used to measure Df and were assessed for their reproducibility in detecting retinal vessels of 30 stereoscopic pairs of optic disc color images. Each pair was taken from the same eye with slightly different angles of incidence. Each photograph of the pairs had subtle variations in brightness between areas temporal and nasal to the optic disc.Results: Intragrader reproducibility of Df measurement was similar (intraclass correlation 0.81 and 0.96, respectively) for IRIS-Fractal and SIVA-Fractal. Within-image pair Pearson’s correlation coefficients (r) of Df measurements were moderate for both methods (0.57 and 0.48, respectively).Conclusions: Both nonlinear orthogonal projection and curvature-based retinal vessel segmentation methods were found to be sensitive to variations in image brightness, resulting from iris shadowing associated with different angle of photographic incidence.

Dust storms have been observed to generate significant DC electric fields. Dust devils specifically are a subset of dust storm, with an ordered sense of rotation about a central axis. Observations in Arizona and Nevada have recorded both electric and magnetic fields associated with dust devils. These electromagnetic signatures are important for future space exploration, with charged dust presenting issues for solar power generation and optics as well as the possibility of communication disruption. The likelihood of lightning from dust devils also has implications for the origin of life, and the chemical composition of the Martian surface and atmosphere.Building upon terrestrial observations of dust devils, and other properties of triboelectrically charged particles, a lumped particle methodology for the generation of electromagnetic fields based on fundamental laws of physics is presented. In this model, the particle motion is constrained to a simple harmonic motion, tracing a circle in 2D, with parameterised relationships for the height variation of the dust devil, the charge profile with grain height and the velocity of the rotational motion determined.Results from the simulation of a dust devil with 3.5 metre radius are compared to the measurements from a terrestrial dust devil of the same size. With a tuned surface electron density input to an event-driven tribocharging model, calculated electrical and magnetic fields are within a factor of two of the measured values. An idealised 3.5 m radius dust devil with its centre passing directly over magnetic and electric field sensors, has an electric field approaching the terrestrial breakdown field strength. This is consistent with recent observations of electric discharge in the vicinity of a dust devil in the UAE. The vertical and horizontal variation of the electric and magnetic field in the vicinity of the dust devil can now be predicted, and the model can readibly be used to interpret field observations on Earth, lander measurements on Mars, and predict signals in future instrument deployments to inform sensor design.

In this century, water scarcity is one of the most crucial issues to be resolved. A practical substitute for resolving this problem is seawater desalination. Membrane-based technologies (e.g., membrane distillation, reverse osmosis, and pervaporation) are compelling and sufficiently proposed for water desalination purposes. However, polymers face some issues like degradation and low penetrability of water and increase energy consumption and overall water desalination costs. 2D nanoporous materials such as graphene oxide, MXenes, metal organic frameworks (MOFs), transition metal dichalcogenides (TMDCs), boron nitrides nanosheets, zeolite, MoS2, etc., with large surface area, mechanical strength, and having atomically thin structure are regarded to be the ideal substitution for water purification and desalination. 2D nanomaterials-based membranes have been used to increase the membrane's overall performance in desalination and water purification. Nevertheless, these nanomaterials’ exceptional properties can lower the energy consumption and increase the efficiency for desalination, which led to the immense attempt in fabrication and commercialization. Here, we have discussed the synthesis, properties, and water purification/desalination performance of 2D nanomaterials-based membranes.Keywords2D nanomaterialsMembranesWater desalinationWater purification

Despite the widespread use of reverse osmosis (RO) membranes in water desalination, the role of solute-membrane interactions in solute transport remains complex and relatively not well understood. This study elucidates the relationship between solute-membrane electrostatic interactions and solute permeability in RO membranes. The transport of salt and neutral molecules through charged polyamide (PA) and uncharged cellulose triacetate (CTA) RO membranes was examined. Results show that salt rejection and salt permeability in the PA membrane are highly dependent on the solution pH due to the variations of membrane charge density and the Donnan potential at the membrane-solution interface. Specifically, a higher salt rejection (and hence lower salt permeability) of the PA membrane is observed under alkaline conditions compared to acidic conditions. This observation is attributed to the enhanced Donnan potential at higher solution pH, which hinders co-ion partitioning into the membrane. In contrast, for salt transport through the CTA membrane and neutral solute transport through both membranes, solute permeability is independent of the solution pH and solute concentration due to the negligible Donnan effect. Overall, our results demonstrate the important role of solute-membrane electrostatic interactions, combined with steric exclusion, in regulating solute permeability in RO membranes.