scholarly journals Benefits and drawbacks of applied direct currents for soil improvement via carbonate mineralization

2020 ◽  
Vol 195 ◽  
pp. 05007
Author(s):  
Dimitrios Terzis ◽  
Patrick Hicher ◽  
Lyesse Laloui
Keyword(s):  
Spatial Distribution ◽  
Electric Fields ◽  
Soil Improvement ◽  
Transport Processes ◽  
Particle Charge ◽  
Electric Currents ◽  
Electrically Assisted ◽  
New Vision ◽  
Chemical Conditions ◽  
Specific Line

The study presented herein adopts a new vision of the processes involved in carbonate mineralization induced by MICP from an electrochemical and crystal growth perspective. More precisely a specific line of focus refers to the species involved in the bio-chemical reactions and especially their net particle charge. By altering electro-chemical conditions via the application of direct electric currents, we observe distinctive trends related to: (i) overall reaction efficiency; (ii) carbonate mineralization/dissolution and (iii) spatial distribution of precipitates. The study introduces the concept of EA-MICP which stands for Electrically Assisted MICP as a means of improving the efficiency of soil bio-consolidation and overcoming various challenges which were previously reported in conventional MICP-based works. Results reveal both the detrimental and highly beneficial role that electric currents can hold in the complex, reactive and transport processes involved. An interesting finding is the “doped” morphology of calcite crystals, precipitated under electric fields, validated by microstructural observations.

scholarly journals Direct currents stimulate carbonate mineralization for soil improvement under various chemical conditions

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Dimitrios Terzis ◽  
Patrick Hicher ◽  
Lyesse Laloui
Keyword(s):  
Electric Fields ◽  
Textural Properties ◽  
Soil Improvement ◽  
Transport Processes ◽  
Electric Currents ◽  
Electric System ◽  
Beneficial Effects ◽  
Treatment Conditions ◽  
Microbially Induced Carbonate Precipitation ◽  
Chemical Conditions

Abstract The present study integrates direct electric currents into traditional calcium carbonate mineralization to investigate electrochemical interactions and the subsequent crystalline growth of CaCO3 bonds in sand. A specific line of focus refers to the effect of three chemical reactive species involved in the stimulated geo-chemo-electric system, namely CaCl2, Ca(CH3COO)2 and Ca(CH3CH2(OH)COO)2. By altering treatment conditions and the applied electric field, we capture distinctive trends related to the: (i) overall reaction efficiencies and distribution of CaCO3 crystals is sand samples; (ii) promotion of CaCO3 mineralization due to DC (iii) crystallographic and textural properties of mineralized bonds. The study introduces the concept of EA-MICP which stands for Electrically Assisted Microbially Induced Carbonate Precipitation as a means of improving the efficiency of soil bio-cementation compared to traditional MICP-based works. Results reveal both the detrimental and highly beneficial effects that electric currents can hold in the complex, reactive and transport processes involved. An interesting observation refers to the “doped” morphology of CaCO3 crystals, which precipitate under electric fields, validated by crystallographic analyses and microstructural observations.

A Case for Magneto Hydro Dynamics (MHD)

2001 ◽  
Author(s):  
Haim H. Bau
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Flux ◽  
Lorentz Force ◽  
Electric Fields ◽  
Biological Fluids ◽  
Fluid Volume ◽  
Chaotic Advection ◽  
Complex Flows ◽  
Electric Currents

Abstract In this paper, I review some of our work on the use of magneto hydrodynamics (MHD) for pumping, controlling, and stirring fluids in microdevices. In many applications, one operates with liquids that are at least slightly conductive such as biological fluids. By patterning electrodes inside flow conduits and subjecting these electrodes to potential differences, one can induce electric currents in the liquid. In the presence of a magnetic field, a Lorentz force is generated in a direction that is perpendicular to both the magnetic and electric fields. Since one has a great amount of freedom in patterning the electrodes, one can induce forces in various directions so as to generate complex flows including “guided” flows in virtual, wall-less channels. The magnetic flux generators can be either embedded in the device or be external. Despite their unfavorable scaling (the magnitude of the forces is proportional to the fluid volume), MHD offers many advantages such as the flexibility of applying forces in any desired direction and the ability to adjust the magnitude of the forces by adjusting either the electric and/or magnetic fields. We provide examples of (i) MHD pumps; (ii) controlled networks of conduits in which each conduit is equipped with a MHD actuator and by controlling the voltage applied to each actuator, one can direct the liquid to flow in any desired way without a need for valves; and (iii) MHD stirrers including stirrers that exhibit chaotic advection.

Atomic origins of molecular polarizabilities

1996 ◽  
Vol 74 (6) ◽  
pp. 1131-1138 ◽  
Author(s):  
Keith E. Laidig
Keyword(s):  
Carbon Monoxide ◽  
Spatial Distribution ◽  
Quantum Mechanics ◽  
Key Words ◽  
Electric Fields ◽  
Polarizability Tensor ◽  
Electronic Charge ◽  
Field Gradients ◽  
Carbon Sulfide ◽  
Molecular Polarizabilities

We demonstrate that the multipole polarizability tensors of a molecule are expressible as a sum of atomic contributions, each of which is based upon the change in the spatial distribution of electronic charge within each atom resulting from the application of electric fields and field gradients. The use of the spatially defined atoms of subsystem quantum mechanics correctly partitions molecular polarizabilities into physically meaningful atomic contributions. It is shown that the origin of any molecular polarizability tensor may be understood from an investigation of these contributions and the general expressions for the summation of atomic components to yield molecular polarizabilities are presented. Their use is demonstrated by the construction and investigation of the axial components of the dipole–dipole dipole–quadrupole, and quadrupole–quadrupole polarizability tensors of carbon monoxide and carbon sulfide. Key words: atomic polarizabilities, atoms-in-molecules, molecular polarizabilities.

Electrically Assisted Aerosol Reactors using Ring Electrodes

1998 ◽  
Vol 520 ◽  
Author(s):  
H. Briesen ◽  
A. Fuhrmann ◽  
S. E. Pratsinis
Keyword(s):  
Particle Size ◽  
Electric Fields ◽  
Optical Fibers ◽  
Total Production ◽  
Electrical Fields ◽  
Synthesis Of Nanoparticles ◽  
Practical Applications ◽  
Electrically Assisted ◽  
Aerosol Reactors ◽  
Electrostatic Dispersion

ABSTRACTNanostructured materials have distinctly different properties than the bulk because the number of atoms or molecules on their surface is comparable to that inside the particles creating a number of new materials and applications. Despite this potential for nanoparticles, very few practical applications have been developed because of the current high cost of these materials ($100/lb). On the other hand, flame aerosol reactors are routinely used for inexpensive production (∼$1/lb) of submicron sized commodities such as carbon blacks, pigmentary titania, fumed silica and preforms for optical fibers in telecommunications. Flame technology can be used also for synthesis of nanoparticles with precisely controlled characteristics. In these reactors, gas mixing is used to widely control the primary particle size and crystallinity of product powders while electric fields can be used to narrowly control the primary, and aggregate particle size and crystallinity. Here the application of axial electrical fields on a silica producing flame using hexamethyldisiloxane (HMDS) as precursor is presented. Experiments varying the precursor delivery rate corresponding to total production rates of 10, 20 and 30 g/h are presented. Electric fields decreased the particle size by electrostatic dispersion and repulsion of charged particles and by the reduced particle residence time inside the flame.

Spatial distribution of active sites on a ferroelectric PbTiO3 photocatalyst for photocatalytic hydrogen production

2017 ◽  
Vol 198 ◽  
pp. 463-472 ◽  
Author(s):  
Rengui Li ◽  
Yue Zhao ◽  
Can Li
Keyword(s):  
Spatial Distribution ◽  
Hydrogen Production ◽  
Solar Energy ◽  
Energy Conversion ◽  
Electric Fields ◽  
Charge Separation ◽  
Active Sites ◽  
Solar Energy Conversion ◽  
Photogenerated Electrons ◽  
The Right

The separation of photogenerated charge carries is a challenging issue in artificial photocatalyst systems for solar energy conversion. It has been reported that spatial charge separation can take place between different facets of semiconductor-based crystals with regular morphology and facets, which could be used to rationally deposit cocatalysts on the right facets. However, the spatial separation of photogenerated electrons and holes is still a big challenge for a particulate photocatalyst without regular morphology and specific facets. In this work, we demonstrated that photogenerated electrons and holes can be regularly separated on ferroelectric PbTiO3 photocatalyst even without regular morphology and facets. The reduction cocatalyst and oxidation cocatalyst could be selectively formed on different sites via an in situ photochemical deposition method. It is found that the photoactivity and hydrogen production for PbTiO3 with spatially separated dual-cocatalysts is remarkably enhanced to more than 100 times greater compared to native PbTiO3, which is much higher than that the case of dual-cocatalysts with a random distribution. The intrinsic electric fields and spontaneous electric polarization in the bulk of PbTiO3 are proposed to play important roles in the spatial distribution of active sites on irregular PbTiO3 particles. Our work emphasizes the essential roles of two important factors, efficient charge separation strategy and the location of dual-cocatalysts on the right sites, to construct integrated artificial photocatalyst systems for solar energy conversion.

The origin of fluctuations and cross-field transport in idealized magnetic confinement systems

1981 ◽  
Vol 300 (1456) ◽  
pp. 547-557 ◽  
Keyword(s):  
Electric Fields ◽  
High Frequency ◽  
Scaling Laws ◽  
Scaling Law ◽  
Low Frequency ◽  
Magnetic Confinement ◽  
Upper Bounds ◽  
Transport Processes ◽  
General View ◽  
Long Wavelength

The study of plasma fluctuations and confinement in idealized systems such as octupoles and levitrons has contributed to the understanding of cross-field transport processes. The linear theory of plasma instabilities that cause fluctuations is well developed and can predict growth rates γ and wavelengths θ x around lines of force. However, the theoretical prediction of cross-field transport coefficient D ± is restricted to quasilinear estimates of upper bounds (for example, D = 1 2 γ λ x 2 ) because of the complexity of the full nonlinear calculation. Such quasilinear estimates usually far exceed the measured values and are of limited worth. A general view of the results from octupole and levitron experiments shows that under collisional conditions ( λ ei / L < 0 ) the diffusion coefficient, D , scales in the same way as classical collisional diffusion ( D α n / T e 1 2 B 2 ). Agreement is closely approached in many cases, sometimes even in the presence of fluctuations. Under collisionless conditions ( D α n / T e 1 2 B 2 ), Bohm diffusion scaling ( D α T e / B ) is found in the few cases where the scaling law has been determined. This behaviour is consistent with the general scaling laws of Connor & Taylor (1977) but is not understood in detail. In addition there is evidence, both experimental and theoretical, that long-wavelength low-frequency electric fields (convection cells) can be generated nonlinearly from high-frequency fluctuations and can contribute to cross-field transport

scholarly journals Spatial distribution of salinity, mud thickness and slope along mangrove ecosystem of the coast of Kupang District, East Nusa Tenggara, Indonesia

2019 ◽  
Vol 20 (6) ◽  
Author(s):  
JERIELS MATATULA ◽  
ERNY POEDJIRAHAJOE ◽  
SATYAWAN PUDYATMOKO ◽  
RONGGO SADONO
Keyword(s):  
Spatial Distribution ◽  
Sea Water ◽  
Mangrove Ecosystem ◽  
Scientific Data ◽  
Systematic Sampling ◽  
Mangrove Forests ◽  
Entire Study ◽  
Distribution Maps ◽  
Physico Chemical ◽  
Chemical Conditions

Abstract. Matatula J, Poedjirahajoe E, Pudyatmoko S, Sadono R. 2019. Spatial distribution of salinity, mud thickness and slope along mangrove ecosystem of the coast of Kupang District, East Nusa Tenggara, Indonesia. Biodiversitas 20: 1624-1632. Mangrove ecosystem is suffering from continuous damage in terms of quality as well as quantity. Rapid mangrove conversion triggered by the ever-growing human population and activities have affected them adversely and caused mangrove deterioration in the coastal areas of Kupang District, Indonesia. The decline of quality and quantity of mangrove environment has caused highly alarming effects, such as an increase in abrasion, decrease of marine products, and sea-water intrusion. Although various efforts have been deployed for the rehabilitation of mangrove forests, there are no significant results yet. One of the reasons is such efforts are not based on scientific data on suitability of the physico-chemical conditions of the mangrove habitats. The objectives of this study was to analyse the physico-chemical conditions, such as salinity, mud thickness and slope of five selected mangrove locations, namely Tarus, Mata Air, Tanah Merah, Oebelo and Merdeka in Kupang District by systematic sampling method and to prepare spatial distribution maps for each of these parameters. Salinity conditions showed a wide variation in the study locations, starting from 10 ppm to 38.33 ppm. Mud thickness ranged from 20.11 cm to 84.77 cm in the entire study area. The highest mud thickness of 84.77 cm was found in Tanah Merah, followed by Oebelo with the maximum thickness of 74.66 cm, Mata Air with 56.22 cm, Merdeka with 53.66 cm, and the lowest mud thickness was in Tarus with 53.55 cm. Mangrove locations in Kupang District are dominated with 2-3% slope. The study indicated that the habitat conditions in the coastal area of Kupang District are suitable for the growth of mangroves. This study will also provide the basis to plan future mangrove rehabilitation programs in the study area.

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