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Smart water flooding is one of the most promising methods for Enhanced Oil Recovery (EOR). However, the exact mechanism beyond is still unknown and the comprehensive knowledge for ...optimization of the composition of the ions needed for an effective flooding process is not available. In this manner, the interactions of different ions present in the aqueous phase with those components of the oil that can have a certain affinity to water (e.g. asphaltene and maltene) are of great importance. In this research work, the effects of monovalent and divalent ions of different charges (Na+, Cl−, Ca2+, Mg2+, and SO42-) on dynamic interfacial properties of the water/oil system have been studied using profile analysis tensiometry (PAT) experimental method. It is demonstrated that participation of the ions from the water phase into the electrostatic interactions with oil, depends on the surface charge of different components of the oil that adsorb at interface. For a better understanding of this matter, separate solutions of the extracted asphaltene in toluene and maltene (de-asphalted oil using heptane) were prepared and used for comparative studies. The results illustrate a major role for the cations, while changes of the anions show negligible effects in our case studies. Among the cations, Mg2+ and Ca2+ show very significant effects on interfacial properties of the related brine-oil interface while Na+ shows negligible effects. The results also demonstrate more significant interaction of the resin components with divalent cations (Mg2+ and Ca2+) in comparison with the asphaltene components. In particular, Mg2+ shows a stronger interaction with both resin and asphaltene molecules in comparison with Ca2+. The measured interfacial elasticity results provide us very helpful complementary data for better understanding of the approximate size and concentration of the adsorbed molecules/aggregates, that support these findings well.
A quantum emitter efficiently coupled to a nanophotonic waveguide constitutes a promising system for the realization of single-photon transistors, quantum-logic gates based on giant single-photon ...nonlinearities, and high bit-rate deterministic single-photon sources. The key figure of merit for such devices is the β factor, which is the probability for an emitted single photon to be channeled into a desired waveguide mode. We report on the experimental achievement of β=98.43%±0.04% for a quantum dot coupled to a photonic crystal waveguide, corresponding to a single-emitter cooperativity of η=62.7±1.5. This constitutes a nearly ideal photon-matter interface where the quantum dot acts effectively as a 1D "artificial" atom, since it interacts almost exclusively with just a single propagating optical mode. The β factor is found to be remarkably robust to variations in position and emission wavelength of the quantum dots. Our work demonstrates the extraordinary potential of photonic crystal waveguides for highly efficient single-photon generation and on-chip photon-photon interaction.
Seawater intrusion (SWI) is one of the most challenging and widespread environmental problems that threaten the quality and sustainability of fresh groundwater resources in coastal aquifers. The ...excessive pumping of groundwater, associated with the lack of natural recharge, has exacerbated the SWI problem in arid and semi-arid regions. Therefore, appropriate management strategies should be implemented in coastal aquifers to control the impacts of SWI problems, considering acceptable limits of economic and environmental costs. The management of coastal aquifers involves the identification of an acceptable ultimate landward extent of the saline water body and the calculation of the amount of seaward discharge of freshwater that is necessary to keep the saline–freshwater interface in a seacoast position. This paper presents a comprehensive review of available hydraulic and physical management strategies that can be used to reduce and control SWI in coastal aquifers. Advantages and disadvantages of the different approaches are presented and discussed.
A large amount of coal fly ash produced in thermal power plants is disposed of in landfills which causes many environmental problems. The utilization of fly ash can be encouraged in geotechnical ...engineering projects. In this paper, the effects of class C and class F fly ash on the mechanical and microstructural behavior and stabilization of clay soil were evaluated through a program of laboratory experiments. The experiments included compaction, unconfined compressive strength, consolidated-undrained triaxial, one-dimensional consolidation tests, and scanning electron microscopy analysis on samples of fly ash-stabilized clay soil after 1, 7, and 28 days of curing. The tests were conducted on mixtures of clay with class C or class F fly ash, ranging from 0% to 30% of the soil. Experimental results showed that the strength parameters and permeability of the stabilized soil improved while the compression and swelling indices decreased by the addition of fly ash and by the increase of curing days. The results obtained from the mechanical tests agreed with the results from the SEM analysis. Based on the results, the soil could be successfully stabilized by using class C fly ash. The improvements in strength, swelling, and permeability parameters of the stabilized soil were higher with the class C fly ash compared with class F fly ash.
In this paper, a typical combined cycle power generation unit in Iran is simulated by a mathematical method in order to perform sensitivity analysis on environmental emission and electricity price. ...The results of this study demonstrate that the efficiency of the power plant depends on both gas turbine design parameters such as gas turbine inlet temperature, compressor pressure ratio and steam cycle design parameters such as HRSG pinch point temperature, condenser pressure. The results demonstrate that an increase in TIT and compressor pressure ratio have a significant effect on exergy efficiency and destruction.
We demonstrate a single-photon collection efficiency of (44.3 + or - 2.1)% from a quantum dot in a low-Q mode of a photonic-crystal cavity with a single-photon purity of g super((2)) (0) = (4 + or - ...5)% recorded above the saturation power. The high efficiency is directly confirmed by detecting up to 962 + or - 46 kilocounts per second on a single-photon detector on another quantum dot coupled to the cavity mode. The high collection efficiency is found to be broadband, as is explained by detailed numerical simulations. Cavity-enhanced efficient excitation of quantum dots is obtained through phonon-mediated excitation and under these conditions, single-photon indistinguishability measurements reveal long coherence times reaching 0.77 + or - 0.19 ns in a weak-excitation regime. Our work demonstrates that photonic crystals provide a very promising platform for highly integrated generation of coherent single photons including the efficient out-coupling of the photons from the photonic chip.
Strong non-linear interactions between photons enable logic operations for both classical and quantum-information technology. Unfortunately, non-linear interactions are usually feeble and therefore ...all-optical logic gates tend to be inefficient. A quantum emitter deterministically coupled to a propagating mode fundamentally changes the situation, since each photon inevitably interacts with the emitter, and highly correlated many-photon states may be created. Here we show that a single quantum dot in a photonic-crystal waveguide can be used as a giant non-linearity sensitive at the single-photon level. The non-linear response is revealed from the intensity and quantum statistics of the scattered photons, and contains contributions from an entangled photon-photon bound state. The quantum non-linearity will find immediate applications for deterministic Bell-state measurements and single-photon transistors and paves the way to scalable waveguide-based photonic quantum-computing architectures.
The use of electro-osmosis for treatment of soft clay soils is a common ground improvement technique. A number of chemical, physical and mechanical interactions occur during the improvement of soil ...by this technique. This paper presents the results of an experimental study on the effects of treatment on the settlement and chemical and physical reactions of a clay soil. A series of experiments were conducted in a designed apparatus with electrical vertical drains (EVD) under different voltages. The experimental results showed that pH, electrical conductivity (EC) and Atterberg limits changed during the tests. In addition, electro-osmosis caused a significant increase in the settlement and undrained strength of the soil.
•pH and EC of anode and cathode reservoirs are dependent on the applied voltage.•Efficiency factor (β) is dependent on the applied voltage.•Electro-osmotic permeability (Ke) is dependent on the time and applied voltage.•Changes of the Atterberg limits leading to an increase in shear strength of the soil
Nature-based solutions (NBS) support the provision of multiple benefits for the environment and society. First idealised in 2008, NBS are recommended by worldwide reports and guidelines as strategies ...to protect, sustainably manage and restore ecosystems. However, their operationalisation is still in the early stages, especially in developing countries, and only a few studies consider their full potential. This article contributes to this context by developing an integrated framework, with spatial and participatory tools, for analysing flood risk mitigation in Brazil. The approach enables a deep understanding of the societal challenges and vulnerabilities of the area (i.e., NEEDS) for subsequently planning the appropriate NBS (i.e., ACTIONS), with the participation of 255 stakeholders of Campina Grande municipality. Results show mappings of flood-prone areas, in which approximately 52% of the flooded areas will see an increase in the future. Hotspots (i.e., hazard, vulnerability, and exposure) are shown and discussed with four application cases. Finally, multiple benefits of seven NBS alternatives are analysed in 53 scenarios of application, in which the higher rates of reductions are found to combined alternatives. The discussion emphasizes the importance of spatially assessing the 'needs' and 'multiple benefits' of NBS, including reducing vulnerabilities and increment of resilience.
The persistent motility of individual constituents in microbial suspensions represents a prime example of the so-called active matter systems. Cells consume energy, exert forces and move, overall ...releasing the constraints of equilibrium statistical mechanics of passive elements and allowing for complex spatio-temporal patterns to emerge. Moreover, when subject to physico-chemical stimuli their collective behaviour often drives large-scale instabilities of a hydrodynamic nature, with implications for biomixing in natural environments and incipient industrial applications. In turn, our ability to exert external control of these driving stimuli could be used to govern the emerging patterns. Light, being easily manipulable and, at the same time, an important stimulus for a wide variety of microorganisms, is particularly well suited to this end. In this paper, we will discuss the current state, developments and some of the emerging advances in the fundamentals and applications of light-induced bioconvection with a focus on recent experimental realizations and modelling efforts. This article is part of the theme issue 'Stokes at 200 (part 2)'.
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