Wetting sub-nanochannels via ionic hydration effect for improving charging dynamics

The ionic transport in sub-nanochannels plays a key role in energy storage,yet suffers from a high energy barrier.Wetting sub-nanochannels is crucial to accelerate ionic transport,but the introduction of water is challenging because of the hydrophobic extreme confinement.We propose wetting the channels by the exothermic hydration process of pre-intercalated ions,the effect of which varies distinctly with different ionic hydration structures and energies.Compared to the failed pre-intercalation of SO_(4)^(2-),HSO_(4)^(-) with weak hydration energy results in a marginal effect on the HOMO(Highest Occupied Molecular Orbital)level of water to avoid water splitting during the electrochemical intercalation.Meanwhile,the ability of water introduction is reserved by the initial incomplete dissociation state of HSO_(4)^(-),so the consequent exothermic reionization and hydration processes of the intercalated HSO_(4)^(-) promote the water introduction into sub-nanochannels,finally forming the stable confined water through hydrogen bonding with functional groups.The wetted channels exhibit a significantly enhanced ionic diffusion coef-ficient by~9.4 times.

Characterization and modeling of long-term stress-strain behavior of water confined pre-saturated gypsum rock in Kurdistan Region,Iraq

In order to understand the effects of soaking time and confined water pressure on the strength of rock due to dissolution of gypsum,rock samples with 96% of gypsum content collected from Kurdistan Region in northern Iraq were investigated.Laboratory tests were then performed on the normal gypsum rock samples under pre-saturated condition to obtain their uniaxial compressive strength(UCS) values.The pre-saturated samples were submerged in distilled water for 35 d,70 d and 105 d,respectively,under confined water pressures of 0-0.5 MPa.The gypsum content decreased by 11% after 105 d of soaking under confined water pressure of 0.5 MPa.The UCS of the normal gypsum rock was 19.6 MPa and it decreased to 6.3 MPa and 2 MPa after 105 d of soaking under confined water pressures of 0 and 0.5 MPa,respectively.A nonlinear constitutive model was used to simulate the experimental stress-strain relationships of rock samples under various conditions.The constitutive model parameters were sensitive to the gypsum content.

Nano-/Micro-confined Water in Graphene Hydrogel as Superadsorbents for Water Purification

Confined water has been proven to be of great importance due to its pervasiveness and contribution to life and many fields of scientific research.However,the control and characterization of confined water are a challenge.Herein,a confined space is constructed by flexibly changing the pH of a graphene oxide dispersion under the self-assembly process of a graphene hydrogel(GH),and the confined space is adjusted with variation from 10.04 to 3.52 nm.Confined water content in GH increases when the pore diameter of the confined space decreases;the corresponding adsorption capacity increases from 243.04 to 442.91 mg g−1.Moreover,attenuated total reflectance Fourier transform infrared spectroscopy and Raman spectroscopy are utilized to analyze the hydrogen bonding structure qualitatively and quantitatively,and correlation analysis reveals that the improvement in the adsorption capacity is caused by incomplete hydrogen bonding in the confined water.Further,confined water is assembled into four typical porous commercial adsorbents,and a remarkable enhancement of the adsorption capacity is achieved.This research demonstrates the application potential for the extraordinary properties of confined water and has implications for the development of highly effective confined water-modified adsorbents.

Vibrational features of confined water in nanoporous TiO_2 by Raman spectra

Raman spectra of confined water adsorbed in nanoporous TiOare obtained in experiment. TiOsamples with different pore diameters under different humidity conditions are investigated. The results indicate that the symmetric vibrational mode of water molecule is destroyed when relative humidity decreases. This indicates that the interaction between water molecules and surface of TiObecomes stronger when the distance between water molecules and surface turns smaller, and the interaction plays a major role in depressing the symmetric vibrational peak. The spectra of confined water in TiOand Vycor are compared. When filling fractions are the same, their spectra show distinctions no matter whether they are in partial filling condition or in full filling condition. The spectra of HDO confined in TiOwith different filling fractions are compared with each other. There is no clear distinction among their vibrational peaks, and the peaks mainly relate to asymmetric vibration. Therefore, the interaction between water molecules and the wall of pore decouples the symmetric vibrational mode only, and the influences on asymmetric vibrational mode show little differences among different filling fractions.

Layering of confined water between two graphene sheets and its liquid-liquid transition

Molecular dynamics （MD） simulations are performed to explore the layering structure and liquid-liquid transition of liquid water confined between two graphene sheets with a varied distance at different pressures. Both the size of nanoslit and pressure could cause the layering and liquid-liquid transition of the confined water. With increase of pressure and the nanoslit＇s size, the confined water could have a more obvious layering. In addition, the neighboring water molecules firstly form chain structure, then will transform into square structure, and finally become triangle with increase of pressure. These results throw light on layering and liquid-liquid transition of water confined between two graphene sheets.

Investigation on the relation between the gravity anomaly，crustal deformation and underground water

Trough the practice of earthquake prediction we have found that sometimes an earthquake doesn' t occur in the gravity anomaly region or the magnitude of earthquake that has occurred does not corrrespond to the value of gravity anomaly. The main reason of this is related to crust deformation or behavior of undergroud water.In this paper, based on the theory of elasticity and dynamics, the gravity effect associated with the elevation variation, density change and mass migration under the observation point as well as the relationshipe between gravity of feet and crustal activity are studied. The relationship between the variation of gravity and crust vertical deformation, underground water, precipitation are researched; besides the order of magnitude, time and pattern of the influence are studied in order to obtain the gravitational precursors directly related to earthquakes.Theory and practice have proved that crust deformation caused by pumping underground water or extracting petroleum and gravity changes are linearly related. This paper shows that the effect and influence produced by different aquifers to the gravity changes are also different. Phreatic water is the main factor which causes the gravity changes. The second factor is precipitation which influences the humidity of soil, as a result the gravity changes. The confined water, when there is no pumping, whatsoever the rise or fall of its level almost has no influence on the gravity changes.Observation data of Northern China and areas of South-western China verified the consistency of practice with theory.

1D/2D composite subnanometer channels for ion transport:The role of confined water

As a mass transport media,water is an alternative of organic solvent applied in rechargeable batteries,due to its unique properties,including fast ionic migration,easy-processibility,economic/environmental friendliness,and flame retardancy.However,due to the high activity of water molecules in aqueous electrolytes,the corrosion of metal anode,side reactions,and inferior metal electrodeposition behavior leads to unstable cycling performance,poor Coulombic efficiency(CE),and early-staged failure of batteries.Despite several attempts to regulate the activity of water,migration of ions is sacrificed,due to the limited methods to control the water states.Herein,we developed a subnanoscale confinement strategy based on a nacre-like structure to modulate the activity of water in the solid electrolytes.By tuning the ratio between the two-dimensional(2D)vermiculite and one-dimensional(1D)cellulose nanofibers(CNFs),the capillary size in the 1D/2D structure is altered to achieve a fast Zn^(2+)transport.Our dielectric relaxation and molecular dynamics studies indicate that the enhanced Zn^(2+)conductivity is attributed to the fast water relaxation in the precisely defined 1D/2D capillary.Taking advantage of the regulated activity of the confined water in 2D capillary,the composite vermiculite membrane can suppress the corrosion and side reactions between Zn electrode and water molecular,endowing a reversible Zn^(2+)stripping/plating behavior and a stable cycling performance for 900 h.Based on our confinement strategy to control the water states by 1D/2D structures,this work will open an avenue toward aqueous energy storage devices with excellent reversibility,high safety,and long-term stability.

Dynamics of supercooled confined water measured by deep inelastic neutron scattering

In this paper, we present the results of deep inelastic neutron scattering （DINS） measurements on supercooled water confined within the pores （average pore diameter - 20A） of a disordered hydrophilic silica matrix obtained through hydrolysis and polycondensation of the alkoxide precursor Tetra-Methyl- Ortho-Silicate via the sol-gel method. Experiments were performed at two temperatures （250 K and 210 K, i.e., before and after the putative liquid-liquid transition of supercooled confined water） on a ＂wet＂ sample with hydration h -40% w/w, which is high enough to have water-filled pores but low enough to avoid water crystallization. A virtually ＂dry＂ sample at h - 7% was also investigated to measure the contribution of the silica matrix to the neutron scattering signal. As ：is well known, DINS measurements allow the determination of the mean kinetic energy and the momentum distribution of the hydrogen atoms in the system and therefore, allow researchers to probe the local structure of supercooled confined water. The main result obtained is that at 210 K the hydrogen mean kinetic energy is equal or even slightly higher than at 250 K. This is at odds with the predictions of a semi-empirical harmonic model recently proposed to describe the temperature dependence of the kinetic energy of hydrogen in water. This is a new and very interesting result, which suggests that at 210 K, the water hydrogens experience a stiffer intermolecular potential than at 250 K. This is in agreement with the liquid-liquid transition hypothesis.

Centrifuge model test and field measurement analysis for foundation pit with confined water

The similarity law of centrifuge test was developed for the seepage field and stress field of a foundation pit with confined water by analyzing control equations,and a similarity index and a similarity coefficient of centrifuge test were obtained.Based on the deep foundation pit of the Huangxing Road Station of the Shanghai metro line M8,the deformation stability of the pit was tested.Finally,a comparative study was conducted on the test results of the pit deformation and the field measurement results.Comparison results show that the pit deformation regularity of the test is basically identical with that of the field measurement,and the difference in pit deformation between the test and the field measurement is within 50%.The centrifuge model test can effectively simulate the displacement response of the ground and retaining structure during dewatering and excavation for the pit with confined water,which provides a reliable basis for the design and construction of the pit with confined water.

Graphene oxide film for efficient solar desalination under one sun with a confined 2D water path

Subject Code:A04With the support by the National Natural Science Foundation of China and the State Key Program for Basic Research of China,the research team led by Prof.Zhu Jia(朱嘉)at the National Laboratory of Solid State Microstructures,College of Engineering and Applied Sciences,Nanjing University,improved the efficiency of solar desalination using graphene oxide film through suppressing the conduction loss。

Structural properties of water confined by phospholipid membranes

Biological membranes are essential for cell life and hydration. Water provides the driving force for the assembly and stability of many cell components. Here, we study the structural properties of water in a phospholipid membrane. We characterize the local structures, inspecting the intermediate range order （IRO） and adopting a sensitive local order metric recently proposed by Martelli et al. that measures and grades the degree of overlap of the local environment with the structures of perfect ice. Close to the membrane, water acquires a high IRO and changes its dynamical properties; i.e., its translational and rotational degrees of freedom slow in a region that extends over - 1 nm from the membrane interface. Surprisingly, we show that at distances as far as -~ 2.5 mn from the interface, although the bulk-like dynamics are recovered, the IRO of water is still slightly higher than that in the bulk under the same thermodynamic conditions. Therefore, the water-membrane interface has a structural effect at ambient conditions that propagates further than the often-invoked 1-nm length scale. Consequently, this should be considered when analyzing experimental data of water confined by membranes and could help us to understand the role of water in biological systems.

Evaluating acoustic communication performance of micro autonomous underwater vehicles in confined spaces

Micro-sized autonomous underwater vehicles(μAUVs) are well suited to various applications in confined underwater spaces. Acoustic communication is required for many application scenarios of μAUVs to enable data transmission without surfacing. This paper presents the integration of a compact acoustic communication device with a μAUV prototype. Packet reception rate(PRR) and bit error rate(BER) of the acoustic communication link are evaluated in a confined pool environment through experiments while the μAUV is either stationary or moving.We pinpoint several major factors that impact the communication performance. Experimental results show that the multi-path effect significantly affects the synchronization signals of the communication device. The relative motion between the vehicle and the base station also degrades the communication performance. These results suggest future methods towards improvements.

Environmentally sustainable groundwater control during dewatering with barriers:A case study in Shanghai

This paper presents a case study on groundwater control and environmental protection during a deep excavation of the foundation pit for the Liyang Road Station of Metro Line 10 in Shanghai.A three-dimensional finite element simulation model was constructed to quantify the effects of a dewatering process on the environment around the excavation pit.To understand the decrease in the groundwater level around the foundation pit,the ground settlement and groundwater level were studied.During the excavation,environmental protection methods were used in the design of the optimal watering system to check its detrimental environmental effects.The effects of the diaphragm wall and horizontal barrier system were analyzed by varying their insertion depths and the resulting changes in the ground settlement and groundwater level were studied.It was found that increasing the insertion depth of the diaphragm wall reduced settlement near the excavation site but increased the construction costs.The diaphragm wall used in combination with a horizontal barrier was found to be effective in arresting the decrease in groundwater level and reducing settlement around the excavation site.

Flow field simulation of supercritical carbon dioxide jet: Comparison and sensitivity analysis

As a new jet technology developed in recent years, the supercritical carbon dioxide（SC-CO2） jet technology enjoys many advantages when applied in oil and gas explorations. In order to study the properties and parametric influences of the SC-CO2 jet, the flow fields of the SC-CO2 jet are simulated using the computational fluid dynamics method. The flow field of the SC-CO2 is compared with that of the water jet. The influences of several parameters on the flow field of the SC-CO2 jet are studied. It is indicated that like the water jet, the velocity and the pressure of the SC-CO2 jet could be converted to each other, and the SC-CO2 jet can generate a significant impact pressure on the wall, the SC-CO2 jet has a stronger impact pressure and a higher velocity than those of the water jet under the same conditions, the maximum velocity and the impact pressure of the SC-CO2 jet increase with the increase of the nozzle pressure drop, under the stimulation condition of this study, the influence of the SC-CO2 temperature on the impact pressure can be neglected in engineering applications, while the maximum velocity of the SC-CO2 jet increases with the increase of the fluid temperature. This paper theoretically explores the properties of the SC-CO2 jet flow field, and the results might provide a theoretical basis for the application of the SC-CO2 jet in oil and gas well drillings and fracturing stimulations.

Effects of finite water depth and lateral confinement on ships wakes and resistance

Wash waves produced by ships disintegrate river banks and coastal lines. This phenomenon of bank erosion is mainly due to the height of the waves. Various factors govern the formation of these waves and their amplitudes: the geometry of the water channel, the shape and the speed of the boat, etc.. These factors play an important role on the wave generation, in addition on the resistance of the ship and so on its fuel consumption. Whether to study the impact of wash waves on the ship's environment or its resistance, the analysis of the generated wake is essential. Hence a fine characterization of the wave field is necessary. This study proposes a comparison of wakes generated by two generic ships based on a Wigley hull with block coefficients 0.67 and 0.89 respectively representative of maritime and fluvial ships. The wakes generated in deep water and confined water configurations have been measured for different Froude numbers by a non-intrusive optical stereo-correlation method, giving access to a detailed and complete definition of the generated wave fields. The resistance of the ship hulls has been measured in deep and confined water configurations with a hydrodynamic balance. The results permit one to study the influence of both hull and water channel geometries on the ship wake, on the amplitude of the far-field generated waves and on the near-field hydrodynamic response. Moreover, resistance curves are obtained for both configurations and highlight the effect of both hull and water channel geometries on the resistance coefficient of the ship. A comparison of the resistance curves with or without the ship trim is conducted and shows the influence of the trim on the resistance coefficient in the different ship speed regimes.

Responses of the Strata and Supporting System to Dewatering in Deep Excavations

In order to prevent the inrushing caused by deep excavations, dewatering measure has to be adopted to decrease the confined water level. In this study, the responses of the strata and supporting system to dewatering in deep excavations are investigated through numerical simulations and case studies. Coupled fluid-mechanical analyses are performed by the use of the numerical software, FLAC3 D. The responses of the ground settlement,base heave and interior columns to the excavation and dewatering are analyzed. Numerical results indicate that the dewatering measure can effectively reduce the uplift of the subsurface soil in the excavation, and decrease the vertical displacement of the supporting system. In addition, field data of two case histories show the similar responses and confirm the validation of the numerical results. Based on the analyses, dewatering in the confined aquifer is recommended as a construction method for controlling the vertical displacement of the strata and supporting system in deep excavations.