Form and Mechanism of Sulfate Attack on Cement-based Material Made of Limestone Powder at Low Water-binder Ratio under Low Temperature Conditions

The development of strength and the form of attack of cement-based material made of limestone powder at low water-binder ratio under low-temperature sulfate environment were studied. The results indicate that when water-binder ratio is lower than 0.40, the cement-based material with limestone powder has insignificant change in appearance after being soaked in 10% magnesium sulfate solution at low temperature for 120 d, and has significant change in appearance after being soaked at the age of 200 d. Expansion damage and exfoliation occur on the surface of concrete test cube at different levels. When limestone powder accounts for about 28 percent of cementitious material, with the decrease of water-binder ratio, the compressive strength loss has gradually decreased after the material is soaked in the magnesium sulfate solution at low temperature at the age of 200 d. After the specimen with the water-binder ratio of less than 0.4 and the limestone powder volume of greater than 20% is soaked in 10% magnesium sulfate solution at low temperature at the age of 200 d, gypsum attack-led destruction is caused to the concrete test cube, without thaumasite sulfate attack.

Relationship between adjustment of low water level and utilization of water depth in Shashi Reach in middle Yangtze River

Hydrological,sediment,and bathymetric data of the Shashi Reach in the middle Yangtze River for the period of 1975-2018 were collected,and the characteristics of low water level changes and their impacts on utilization of water depth for navigation were investigated.The results showed that,during the study period,the Shashi Reach riverbed was significantly scoured and incised,with cross-sectional profiles showing overall narrowing and deepening.This indicated a strong potential to improve the water depth of the channel.The analysis of the temporal variation of in-channel topographical features showed that the Taipingkou diara underwent siltation and erosion,with its head gradually scoured and relocated downstream after 2008,and the Sanbatan diara continued to shrink and migrate leftwards.Low water levels with the same flow rate over the study period decreased.For instance,from 2003 to 2020,the water level at the Shashi hydrological station decreased to 1.37 m with a flow rate of 6000 m^(3)/s.Furthermore,the designed minimum navigable water level of the Shashi Reach was approximately 2.11m lower than the recommended level.In terms of utilization of the channel water depth,continuous scouring of the river channel is expected to result in a reduction in discharge at the Taipingkou mouth,which will improve the water depth conditions of the channel during the dry season in the Shashi Reach.With several channel regulation projects,the 3.5-m depth of the Shashi Reach would basically be unobstructed.This promotes utilization of the shipping route from the Taipingkou south branch to the Sanbatan north branch as the main navigation channel during the dry season.Considering the factors of current water depth and the clear width limitation of the navigation hole at the Jingzhou Yangtze River Bridge,this route can still be favored as the main navigation channel with a 4.5-m depth during the dry season.

Hydromechanical Behavior of Low-Swelling Soils Compacted at Low Water Content: Laboratory Study

Fine unsaturated soils are used in many applications, particularly in road infrastructure and in construction. These materials undergo deformations according to the stresses to which they are subjected. The purpose of this paper is to study the influence of hydromechanical stresses on the behavior of low swelling soils compacted at low water content in accordance with the French standard GTR 92 (Guide des Terrassements Routiers). Then, various experimental tests on an oedometer were carried out in the laboratory. Two types of low swelling soil sampled in Nasso on the outskirts of the town of Bobo Dioulasso (Burkina Faso) were used. After shuffling, each sample was moistened to its optimum water content and then compacted to 90% and 95% of its optimum density. Behavior tests show that these soils deform very little when subjected to hydromechanical stresses. However, these deformations are swelling in nature for low mechanical stresses and when the stresses are high, they tend to collapse. When these soils are subjected to a vertical stress of 420 kPa, the primary consolidation time is of the order of one minute for NH2 (a silty soil) and about ten minutes for NH3 (a silty-clayed soil).

Tidal Analysis of High and Low Water Data

The harmonic analysis method based on high and low water levels is discussed in this paper. In order to make full use of the information of high and low water observations (the time derivative of water level at the observation time is zero), the weight coefficient, w, is introduced to control the importance of the part related to this information in the error formula. The major diurnal constituents, O 1 and K 1, and semi diurnal constituents, N 2, M 2 and S 2 are selected directly from the monthly data analysis, and some other important constituents, P 1, ν 2 and K 2, are included as the inferred constituents. The obtained harmonic constants of the major constituents are very close to those obtained from the analysis of hourly data, and this shows that high and low water data can be used to extract tidal constants with high accuracy. The analysis result also shows that the inference and the weighting coefficient are important in the high and low water data analysis, and it is suggested that w ≥1 should be taken in monthly high and low water data analysis. This analysis method can be used directly to analyze altimetric data with w =0.

Gas chromatographic thermodynamics on hydration processes of magnesium chloride with low water

The dehydration and hydration processes of magnesium chloride hydrates were studied by means of frontal chromatography analysis, calorimetry, thermogravimetry and chemical analysis. The mathematical imitation for the adsorption isotherms of MgCl 2·4H 2O and MgCl 2·2H 2O at different temperatures indicates that Boltzmann Function is the ideal equation to describe those adsorption isotherms. Its adsorption heat is -13.06 kJ/mol and -16.11 kJ/mol, respectively. The adsorption equilibrium constants are also given. From the data obtained, there is a thermodynamical possibility to use partial dehydrated magnesium chloride hydrates as an absorbance to clean water vapor contained in bischophite dehydration equipment and let the protection gas HCl recycle in the fluid bed reaction system.

A study of low water consumption patterns from the perspective of water footprint:A case of residents' food consumption in Zhangye City

Population growth,technological change and increased consumption are considered to be the main causes of the three environmental crisis.Environmental problems which are due to population growth and technology have already caused widespread concern,and the environmental problems caused by consumption,did not get enough attention and in-depth research.Is consumption a problem? What is the environmental conflict brought about by the consumption? What factors have contributed to the growing consumers? How do the resources meet the high levels of consumption? What is the relationship between consumption and quality of life? How can we alter consumption patterns? From the water footprint theory,this paper discusses the necessity of advocacy at meeting basic human needs while reducing the consumption of water footprint low water consumption patterns,and recommended by the German Nutrition Society DGE healthy eating pattern as a reference,compared with the normal mode of Australia diet county area of Zhangye City in food consumption,water consumption and total consumption of water footprint component characteristics.

The R&D of a Novel Sulfur Tolerant CO Shift Catalyst and Its Application in the Integrated Low Water Gas Ratio Process

The QDB-5 sulfur tolerant CO shift catalyst, with anti-methanation property by supported compositing alkali promoters, has been proved to effectively reduce the outlet methane content in the condition of a low water gas ratio. Thus, a new technology based on a lower water/gas ratio than before has been developed with the new catalyst. The CO conversion at lower temperatures and catalyst stability were confirmed by long term industrial application. The high temperature catalyst performance also showed a better result than the conventional commercial catalyst, with higher CO conversion and well controlled methane outlet. Our research and the industrial application of catalyst have shown the importance of alkali metals as core promoters for such kind of catalysts.

Investigation of low water recovery based on gas-water two-phase low-velocity Non-Darcy flow model for hydraulically fractured horizontal wells in shale

Various mechanisms are employed to interpret the low water recovery during the shale-gas production period,such as extra-trapped water in the fracture network,water imbibition due to osmotic pressure and capillary pressure.These lead to the difficulty of water flow,which could be described by lowvelocity non-Darcy's law known as threshold pressure gradient(TPG).In this paper we firstly employ the low-velocity non-Darcy's law to describe the water flow and use Darcy flow accounting for slip flow and free molecular flow mechanisms to model gas flow in the shale formation.The sensitive study using numerical simulation shows that the proposed flow model could model the low fracturing liquid recovery and that large pseudo TPG leads to lower fracturing liquid recovery.Thus,the proposed model would give new insight to model the low water recovery in shale formations.

Hybrid low salinity water and surfactant process for enhancing heavy oil recovery

Combining low salinity water (LSW) with surfactants has an enormous potential for enhancing oil recovery processes. However, there is no consensus about the mechanisms involved, in addition to the fact that several studies have been conducted in model systems, while experiments with rocks and reservoir fluids are scarce. This study presents a core-flooding experiment of LSW injection, with and without surfactant, using the core and heavy oil samples obtained from a sandstone reservoir in southeastern Mexico. The effluents and the crude oil obtained at each stage were analyzed. The study was complemented by tomographic analysis. The results revealed that LSW injection and hybrid process with surfactants obtained an increase of 11.4 percentage points in recovery factor. Various phenomena were caused by LSW flooding, such as changes in wettability and pH, ion exchange, mineral dissolution, detachment of fines and modification of the hydrocarbon profile. In the surfactant flooding, the reduction of interfacial tension and alteration of wettability were the main mechanisms involved. The findings of this work also showed that the conditions believed to be necessary for enhanced oil recovery with LSW, such as the presence of kaolinite or high acid number oil, are not relevant.

Effects of sediment parameters on the low frequency acoustic wave propagation in shallow water

The integral expression for acoustic field due to a point source in shallow waterwhile sediment is either a liquid or a solid is derived. The synthetic full waveforms are simulatedusing real axis integration and FFF method. The effects of the seabed sediment parametersand center frequency of the source on the low frequency acoustic wave propagation in shallowwater are investigated. The conclusion is that the wave groups received in far field are thoseof the mode waves of the source center frequency. The possibility for inversely deducing thecompressional and shear sound speeds of sediment using the least square optimum through themeasured group velocities of a selected mode at different frequencies is discussed.

Contributions of annual and semiannual tidal constituents to chart datum in the China seas and adjacent waters

Global uniform chart datum(CD)surface construction is the basic upon which to realize various vertical datums transformation,and is of great importance for geospatial data expression under the same vertical datum.Generally,the CD level is computed by developing the function between tidal constituents’harmonic constants and time,i.e.,the lowest astronomical tide is taken as the lowest predicted tide level by adopting the major constituents over a 19-a period.The CD surface prescribed in China is the theoretical lowest tide(TLT)and is calculated using 13 tidal constituents,i.e.,short-period(Q_(1),O_(1),P_(1),K_(1),N_(2),M_(2),S_(2),K_(2),M_(4),MS_(4)and M_(6))and long-period(Sa and Ssa)tidal constituents.Although the accuracy in determining short-period tidal constituents has improved gradually,the long-period tide has not been studied thoroughly owing to nonstationary and temporal variations.Previous studies have intended to evaluate the effect of Sa and Ssa tides in the determination of the TLT level for the purpose of determining a more accurate CD surface for the China seas and adjacent waters.Here,the parameters of long-period tidal correction and long-period tidal correction rate were treated as the effect of both Sa and Ssa on the TLT,and the TOPEX/Poseidon and Jason series satellite altimetry data ranged from October 1992 to April 2022 were adopted to analyze the contribution of long-period tidal constituents.Results showed that the average long-period correction value is 10.10 cm(range from 8.57 cm to 14.98 cm),and that the average long-period tidal contribution rate is 14.56%(range from 9.09%to 23.97%)in the China seas and adjacent waters.Finally,data from 82 tide gauge station with at least a 1-a record of hourly observations were compared with satellite-derived result.We concluded that the long-period tidal contribution should not be neglected in TLT construction.Furthermore,to reduce tidal datum uncertainty,accurate extraction of long-period tidal constituents should receive closer attentions.

Enhanced oil recovery from carbonate reservoirs by spontaneous imbibition of low salinity water

An experimental study was performed to investigate the impact of low salinity water on wettability alteration in carbonate core samples from southern Iranian reservoirs by spontaneous imbibition. In this paper, the effect of temperature, salinity,permeability and connate water were investigated by comparing the produced hydrocarbon curves. Contact angle measurements were taken to confirm the alteration of surface wettability of porous media. Oil recovery was enhanced by increasing the dilution ratio of sea water, and there existed an optimum dilution ratio at which the highest oil recovery was achieved. In addition, temperature had a very significant impact on oil recovery from carbonate rocks. Furthermore, oil recovery from a spontaneous imbibition process was directly proportional to the permeability of the core samples. The presence of connate water saturation inside the porous media facilitated oil production significantly. Also, the oil recovery from porous media was highly dependent on ion repulsion/attraction activity of the rock surface which directly impacts on the wettability conditions. Finally, the highest ion attraction percentage was measured for sodium while there was no significant change in pH for all experiments.

Performance of low-salinity water flooding for enhanced oil recovery improved by SiO_2 nanoparticles

Low-salinity water injection has been utilized as a promising method for oil recovery in recent years. Low-salinity water flooding changes the ion composition or brine salinity for improving oil recovery. Recently, the application of nanoparticles with low-salinity water flooding has shown remarkable results in enhanced oil recovery(EOR). Many studies have been performed on the effect of nanofluids on EOR mechanisms. Their results showed that nanofluids can improve oil recovery when used in low-salinity water flooding. In this work, the effects of injection of low-salinity water and low-salinity nanofluid(prepared by adding SiO_2 nanoparticles to low-salinity water) on oil recovery were investigated. At first, the effects of ions were investigated with equal concentrations in low-salinity water flooding. The experimental results showed that the monovalent ions had better performance than the divalent ions because of them having more negative zeta potential and less ionic strength. Also, low-salinity water flooding recovered 6.1% original oil in place(OOIP) more than the high-salinity flooding. Contact angle measurements demonstrated that low-salinity water could reduce the contact angle between oil and water. Then in the second stage, experiments were continued by adding SiO_2 nanoparticles to the K+ solution which had the highest oil recovery at the first stage. The experimental results illustrated that the addition of Si02 nanoparticles up to 0.05 wt% increased oil recovery by about 4% OOIP more than the low-salinity water flooding.

Pilot scale treatment of low turbidity water using compound bioflocculant and polymerized aluminium ferrum chloride

To investigate the application of compound bioflocculant (CBF) in drinking water treatment at pilot plant,CBF and polymerized aluminium ferrum chloride (PAFC) coagulant were used to treat raw water taken from Longhupao Reservoir in Heilongjiang Province for the removal of turbidity,COD,UV254 and residual Al. Coagulation test shows that the coagulation enhanced by CBF and PAFC exhibits more effective performance than that enhanced by the individual of them,and the total combination dosage is lower than that of the individual. The residual Al from PAFC can be removed efficiently by CBF. The removal efficiency of turbidity reaches 76.6% by combining CBF of 2 mg/L and PAFC of 15 mg/L,COD is decreased from 3.80 mg/L to 1.62 mg/L,and the concentration of residual Al is only 0.033 mg/L in the product water. It can be speculated that adsorption-bridging and sweep-coagulation processes are predominant in the flocculation process by the combination of CBF and PAFC.

Numerical Simulation and Dynamical Analysis for Low Salinity Water Lens in the Expansion Area of the Changjiang Diluted Water

The low salinity water lenses（LSWLes） in the expansion area of the Changjiang diluted water（CDW） exist in a certain period of time in some years. The impact of realistic river runoff, ocean currents and weather conditions need to be taken into account in the dynamical analysis of LSWL, which is in need of research. In this paper, the POM-σ-z model is used to set up the numerical model for the expansion of the CDW. Then LSWL in summer 1977 is simulated, and its dynamic mechanism driven by wind, tide, river runoff and the Taiwan Warm Current is also analyzed. The simulated results indicate that the isolated LSWL detaches itself from the CDW near the river mouth, and then moves towards the northeast region outside the Changjiang Estuary. Its maintaining period is from July 26 to August 11. Its formation and development is mainly driven by two factors. One is the strong southeasterly wind lasting for ten days. The other is the vertical tidal mixing during the transition from neap tide to spring tide.

How much would silica nanoparticles enhance the performance of low-salinity water flooding?

Nanofluids and low-salinity water(LSW)flooding are two novel techniques for enhanced oil recovery.Despite some efforts on investigating benefits of each method,the pros and cons of their combined application need to be evaluated.This work sheds light on performance of LSW augmented with nanoparticles through examining wettability alteration and the amount of incremental oil recovery during the displacement process.To this end,nanofluids were prepared by dispersing silica nanoparticles(0.1 wt%,0.25 wt%,0.5 wt% and 0.75 wt%)in 2,10,20 and 100 times diluted samples of Persian Gulf seawater.Contact angle measurements revealed a crucial role of temperature,where no wettability alteration occurred up to 80 ℃.Also,an optimum wettability state(with contact angle 22°)was detected with a 20 times diluted sample of seawater augmented with 0.25 wt% silica nanoparticles.Also,extreme dilution(herein 100 times)will be of no significance.Throughout micromodel flooding,it was found that in an oil-wet condition,a combination of silica nanoparticles dispersed in 20 times diluted brine had the highest displacement efficiency compared to silica nanofluids prepared with deionized water.Finally,by comparing oil recoveries in both water-and oil-wet micromodels,it was concluded that nanoparticles could enhance applicability of LSW via strengthening wettability alteration toward a favorable state and improving the sweep efficiency.

Efficiency of enhanced oil recovery by injection of low-salinity water in barium-containing carbonate reservoirs

When low-salinity water containing sulfate ions is injected into carbonate reservoirs, rock dissolution and in situ precipitation occur, altering rock permeability and wettability. Particularly, when barium ions are present in formation water,they react chemically with SO;, and BaSO;is precipitated. These reactions can cause a serious impact on the efficiency of enhanced oil recovery（EOR）. Therefore, the main purpose of this study was to identify EOR efficiency induced by lowsalinity waterflooding（LSWF） when Ba;is present in carbonate reservoirs. From the experimental results, it was confirmed that the permeability calculated by the measured pressure difference was improved because of rock dissolution predominating over in situ precipitation for the case of low Ba;concentrations. In the analysis of wettability alteration through the measurements of relative permeabilities before and after LSWF, the higher Ba;concentration case consumed more SO;in precipitating the BaSO;, resulting in weaker wettability alteration due to the reduction of sulfate activity.These phenomena ultimately influenced EOR efficiency, i.e., the oil recovery was greater for the lower Ba;concentration.

Enhanced treatment of water with low turbidity:Combined effects of permanganate, PAM and recycled sludge

The effectiveness of enhancing treatment of water with low turbidity through combined effects of permanganate oxidation, PAM aiding coagulation and sludge recycling was investigated through continuous bench scale studies. In comparing with ferric chloride coagulation, only recycling sedimentation sludge was ineffective in enhancing treatment of water with low turbidity. PAM with recycled sludge showed positive effects, and the additional permanganate dosing exhibited the best potential of favoring coagulation, which leaded to much lower effluent turbidity and CODMn. Additionally, it was observed that the optimal permanganate dosage was 0.4 mg/L and the higher permanganate dosage exhibited inhibiting effects for pollutants removal. SEM analysis indicated that the flocs were loosely formed and the particle diameter was critically low for ferric chloride coagulation process. Comparatively, the addition of PAM and permanganate with recycled sludge facilitated the aggregation of tinny particles onto compact PAM polymer chains, therefore contributing to the formation of compact flocs with high particle diameter. The combined employment of recycled sludge, PAM and permanganate showed the best potential of favoring coagulation, mainly through synergistic effects between seeding, polymer bridging and increasing effective collision in mechanism. Additionally, the variation of Fe and Mn concentration after recycling and sedimentating units was studied for the processes, and the main species was also investigated for elements Fe and Mn. Sludge recycling and permanganate addition did not increase Fe and Mn concentration in the sedimented water.

Impact of Untreated Sedimentation Tank Sludge Water Recycle on Water Quality During Treatment of Low Turbidity Water

The overall purpose of this research is to examine the impact of untreated sedimentation tank sludge water( USTSW) recycle on water quality during treatment of low turbidity water in coagulation—sedimentation processes. 950 m L of raw water and different concentrations of 50 m L USTSW are injected into six 1 000 m L beakers without coagulant.The results indicate that USTSW characterized as accumulated suspended solids and organic matter has active ingredients,which possess the equivalent function of coagulant. The optimal blended water turbidity is in the range of 10-20 NTU,within which USTSW recycle achieves the highest save coagulant rate. The mechanism of strengthening coagulation effect when USTSW recycle mainly depends on the chemical effect and physical effect. What is more,through scanning electron microscopy( SEM),it is found that the floc structures with USTSW recycle are more compact than those without USTSW recycle. Besides,the water quality parameters of color,NH3-N,CODMn,UV254,total aluminum,total manganese when USTSW recycle is better than the raw water without recycle,indicating that USTSW recycle can improve water quality with strengthening coagulation effect.

Effect of various Na/K ratios in low-salinity well water on growth performance and physiological response of Pacific white shrimp Litopenaeus vannamei

To investigate the influence of sodium to potassium(Na/K) ratios on the growth performance and physiological response of the Pacific white shrimp( Litopenaeus vananmei), various concentrations of KCl were added to low-salinity well water(salinity 4) in an 8-week culture trial. Six treatments with Na/K ratios of 60:1, 42:1, 33:1, 23:1, 17:1, and 14:1 were replicated in triplicate. The highest weight-gain rate(3 506±48)% and survival rate(89.38±0.88)% was observed in well water with Na/K ratios of 23:1 and 42:1, respectively, while the feed conversion ratio(1.02±0.01), oxygen consumption, and ammonia-N excretion rate was the lowest in the medium with a Na/K ratio of 23:1. Gill Na +-K +-ATPase activity, as an indicator of osmoregulation, peaked in the treatment where the Na/K ratio was 17:1. The total hemocyte count, respiratory burst, and immune-related enzyme activities(ALP, LSZ, PO, and SOD) of L. vananmei were affected significantly by Na/K ratios( P <0.05). After challenged with Vibrio harveyi, the cumulative mortality of shrimp reared in a Na/K ratio of 23:1(30±14.14)% was significantly lower than the control(75±7.07)%. In conclusion, the addition of K + to low-salinity well water in L. vannamei cultures is feasible. Na/K ratios ranging from 23:1 to 33:1 might improve survival and growth. Immunity and disease resistance are also closely related to the Na/K ratio of the low-salinity well water. The findings may contribute to the development of more efficient K + remediation strategies for L. vananmei culture in low-salinity well water.