Initial Volume Ratio Research Articles

Dynamic analysis of oil-water interface, taking Shunbei oilfield as an example

The oil-water interface changes dynamically as oil is produced. The dynamic analysis of oil-water interface is the key to oil stabilization and water control in Shunbei oilfield. This paper presents a way to investigate oil-water interface behavior by using dynamic data. In this paper, we validated this method available with the actual data. Sensitivity analyses about the effects of the main parameters are also presented in detail. The water breaking time of oil wells is fully investigated. The oil-water interface movement chart under different development conditions is established to predict the oil-water interface in the late stage of oil well production and extend the waterless developing period. Being based on this chart, a water breakthrough warning can be realized, and oil recovery can be improved. The findings of the research have led to the conclusion that the rising speed of oil-water interface is proportional to the production rate, on the contrary, it is inversely proportional to cave volume and initial oil-water volume ratio. This method is not only suitable for any well type; but also has the function of calculating the real-time oil-water interface of multi-wells. This method can be further developed as its great applicability in fracture-cavity reservoir. • The law of oil-water interface movement in Shunbei oilfield is clarified. • The calculation process is simple without measuring the permeability of oil and water phases. • According to the rising rate of oil-water interface, measures to stabilize oil and control water can be developed quickly to improve single well recovery.

Treatment of fishery wastewater by co-culture of Thalassiosira pseudonana with Isochrysis galbana and evaluation of their active components

Microalgae can synthesize their own active substances by absorbing nitrogen, phosphorus in wastewater to provide the nourishing bait for the aquatic organisms, when purifying the aquaculture wastewater. This research Thalassiosira pseudonana (Tp) and Isochrysis galbana (Ig) were selected to treat fishery wastewater and then evaluation of their active components. The results showed that the highest biomass productivity of Tp and Ig was 0.11 g·L−1·day−1 and 0.14 g·L−1·day−1, respectively, at the optimal initial inoculum biomass of 0.4 g·L−1. Furthermore, the two strains were co-cultured in different initial inoculum volume ratios, and the highest biomass was at the volume ratio of 1:1. With the most suitable inoculum biomass and volume ratio, the removal rates of NH4+-N, TN and TP were 80.65%, 85.29% and 92.75%, respectively. Moreover, the cells after wastewater treatment showed high contents of carbohydrate, protein, and lipid, which were 36.62%, 8.72% and 23.11%, respectively. This study showed that co-culturing Thalassiosira pseudonana with Isochrysis galbana to treat fishery wastewater is feasible, and algae cells have high nutritional value, which may provide a feasible technology for ecological protection and resource utilization of aquaculture.

Developing a reclamation strategy for softening nanofiltration brine: A scaling-free conversion approach via continuous two-stage electrodialysis metathesis

A significant amount of concentrated, scaling-prone brine can be generated during the conversion of unconventional water resources to freshwater, thus necessitating the zero discharge of concentrated brine to meet environmental and resource requirements. In this study, a two-stage feed-and-bleed electrodialysis metathesis (FB-EDM) process was implemented to reclaim softening nanofiltration (SNF) brine. To determine the optimized process parameters, experiments were conducted with various initial diluate to concentrate volume ratios (VD:VC), applied voltages, replenishment flow rates (Qrp), and initial diluate compartment concentration ratios (CD1:CD2). The results indicated that these parameters (except for the initial volume ratio) significantly influenced the FB-EDM process. The optimized conditions included a VD:VC of 2:1, voltage of 1.5 V per repeating unit, Qrp of 4 L/h, and CD1:CD2 of 1.5:1. The two-stage FB-EDM process operating under the optimized conditions achieved an energy consumption of <0.9 kWh/kg salt, and the total dissolved solids (TDS) in terms of Cl-type and Na-type salts reached 199.1 and 224.4 g/L, respectively; the corresponding overflow rates were 1.17 and 1.14 L/h, respectively. The developed system thus demonstrated approximately 85% TDS removal and ionic conversion of the brine; additionally, the self-crystallization of CaSO4·2H2O was realized by blending the Cl-type and Na-type salts. This process therefore represents a suitable method for converting SNF brine into highly-concentrated liquid salts, and provides a reclamation strategy for miscellaneous salts.

Improved Operation of Continuous Ozone Hydrate Production

AbstractIn a previous study, we have experimentally demonstrated the continuous formation of O3+O2+CO2 hydrate. Here, improved results for the O3+O2+CO2 hydrate formation are reported. By forming O3+O2+CO2 hydrate at a low temperature and higher O3 gas concentration in the gas phase, the O3 concentration in the hydrates was increased to be 0.41 mass %, which was 1.6 times higher than our past record. One‐quarter reduction of the induction time for O3+O2+CO2 hydrate formation was also achieved by raising the initial volume ratio of CO2 in the feed gas in the range of 2–2.9 times that of our previous study. Also, the overall heat transfer coefficient during O3+O2+CO2 hydrate continuous formation was experimentally determined.

Separation of sodium hydroxide from post-carbonation brines by bipolar membrane electrodialysis (BMED)

Desalination brine is composed of two-fold higher Ca and Mg than seawater and is a promising candidate for the mineral carbonation process to reduce CO2. We previously obtained post-carbonation brine containing Na (2.6–2.8 wt%), Mg (60–147 mg/L), and Ca (4–7 mg/L) after mineral carbonation, followed by a conventional electrodialysis process using desalination brine. In the mineral carbonation process, NaOH was used as an essential reactant. This study aimed to use bipolar membrane electrodialysis (BMED) to produce NaOH solutions (>1.0 M to be recycled during mineral carbonation) from post-carbonation brine containing bivalent Mg ion concentrations >10 mg/L. In this study, we monitored the effects of applied voltage, temperature, the initial volume ratio of solutions (feed, base, and acid compartments), and the initial concentration of the acid/base solution on BMED performance. Proton leakage through the anionic exchange membrane could be utilized for the production of NaOH in the BMED process from Mg-containing brine by varying the volume ratio of the solutions. A total of 2.0 mol/L of NaOH was obtained from a brine containing 147 mg/L of Mg ions. These findings suggest potential efficiencies in the mineral carbonation processing of desalination brines. A further refinement of this method in a cyclic manner can help sequestrate CO2 through the mineral carbonation of desalination brines.

Enhancement of the biohydrogen production performance from mixed substrate by photo-fermentation: Effects of initial pH and inoculation volume ratio

Co-digestion of substrates can improve hydrogen yield (HY) by adjusting carbon nitrogen ratio (C/N) of fermentation substrates. This study evaluated the enhancement of hydrogen production from co-digestion of duckweed and corn straw via photo-fermentation. The maximum HY of 78.0 mL/g Total solid (TS) was obtained from the mixed ratio of 5:1 (C/N of 13.2), which was 25.4% and 29.6% higher than those of single substrate of duckweed and corn straw, respectively. The effects of initial pH and inoculation volume ratio (IVR) on co-digestion photo-fermentative hydrogen production (CD-PFHP) from duckweed and corn straw were further studied. A maximum HY of 85.6 mL/g TS was achieved under the optimal condition (initial pH 8, IVR 20%, mix ratio of duckweed and corn straw of 5:1). Additionally, both mix ratio and initial pH showed statistical difference (p < 0.05). Acetic acid and butyric acid were found to be the main metabolic by-products during CD-PFHP.

Separation of soluble saccharides from the aqueous solution containing ionic liquids by electrodialysis

Ionic liquids are extensively used in many separation processes due to excellent dissolving ability for organic compounds and polymer materials, such as cellulose dissolution, Keratin dissolution. However, during the dissolution process, a small amount of degraded organic saccharides was produced, which could affect the strength of the regenerated fibers. Thus, it is required to find a suitable method for the removal of these saccharide molecules during the process of IL recovery. In this study, electrodialysis (ED) was used for the separation of these saccharide molecules from IL aqueous solution. In order to evaluate the separation performance of ED process, the influences of applied voltage, initial concentrations of IL and saccharide, and the initial volume ratio of the dilute solution to the concentrated solution on the current efficiency (η), recovery ratio (RIL), removal ratio (RS) and energy consumption (E) were systematically investigated. Experimental results showed that ED played a dual role in removing saccharides from the IL aqueous solution and concentrating IL. Under the optimized conditions, the removal efficiency of saccharides was 98.11% and IL concentration ratio is 2.63. Especially, the characterization results identified that the structure of the recovered IL was in well agreement with that of the fresh IL. All of these proved that ED might be an effective and green method to realize the separation of saccharides from the IL aqueous solution.

Biohydrogen production with lipid-extracted Dunaliella biomass and a new strain of hyper-thermophilic archaeon Thermococcus eurythermalis A501

Economic feasibility is important for the development of microalgae bioenergy industry. Dark fermentation of microalgal residue in a biorefinery context can improve the energy conversion efficiency of biomass and reduce the cost of microalgae industry. The present study proposes a promising dark fermentation model that combines thermophilic hydrogen-producing bacteria with algal residue substrates. Lipid-extracted Dunaliella residue can greatly improve hydrogen production by Thermococcus eurythermalis A501, the yields of which are more than four times higher than with algal cells as substrates. Under the optimal conditions of 2.5 g/L algal residue concentration and a 2:1 initial volume ratio of gas to liquid, the highest hydrogen yields of 192.35 and 183.02 mL/g volatile solid (VS) with algal residue of Dunaliella primolecta and D. tertiolecta are obtained, respectively, in less than 19 h without any pretreatment. This work may provide a biorefinery approach for comprehensive utilization of microalgae resources.

A cavity expansion–based solution for interpretation of CPTu data in soils under partially drained conditions

SummaryA cavity expansion–based solution is proposed in this paper for the interpretation of CPTu data under a partially drained condition. Variations of the normalized cone tip resistance, cone factor, and undrained‐drained resistance ratio are examined with different initial specific volume and overconsolidation ratio, based on the exact solutions of both undrained and drained cavity expansion in CASM, which is a unified state parameter model for clay and sand. A drainage index is proposed to represent the partially drained condition, and the critical state after expansion and stress paths of cavity expansion are therefore predicted by estimating a virtual plastic region and assuming a drainage‐index–based mapping technique. The stress paths and distributions of stresses and specific volume are investigated for different values of drainage index, which are also related to the penetration velocity with comparisons of experimental data and numerical results. The subsequent consolidation after penetration is thus predicted with the assumption of constant deviatoric stress during dissipation of the excess pore pressure. Both spherical and cylindrical consolidations are compared for dissipation around the cone tip and the probe shaft, respectively. The effects of overconsolidation ratio on the stress paths and the distributions of excess pore pressure and specific volume are then thoroughly investigated. The proposed solution and the findings would contribute to the interpretation of CPTu tests under a random drained condition, as well as the analysis of pile installation and the subsequent consolidation.

Data-Acquisition Optimization Maximizes Value of Mature Oil-Rim Reservoirs

This article, written by JPT Technology Editor Judy Feder, contains highlights of paper SPE 196208, “Value Creation From the Reservoir, Well, and Facilities Management (RWFM) Planning in Multistacked Mature Oil-Rim Reservoir, Offshore Sarawak, Malaysia,” by Yeek Huey Ho, SPE, Nor Baizurah Ahmad Tajuddin, SPE, Muhammed Mansor Elharith, SPE, Hui Xuan Dan, Kwang Chian Chiew, Kok Liang Tan, SPE, Raj Deo Tewari, SPE, and Rahim Masoudi, SPE, Petronas, prepared for the 2019 SPE Annual Technical Conference and Exhibition, Calgary, 29 September–2 October. The paper has not been peer previewed. The XamXung field offshore Sarawak, Malaysia, is a 47-year brownfield with thin remaining oil rims that have made field management challenging. The dynamic oil-rim movement has been a key subsurface uncertainty, particularly with the commencing of a redevelopment project. A reservoir, well, and facilities-management (RWFM) plan was implemented to optimize development decisions. This paper is a continuation of paper SPE 174638 and outlines the outcome of the RWFM plan and the results’ effect on development decisions such as infill well placement and gas/water injection-scheme optimization (Fig. 1). Key decisions affected by the RWFM findings are highlighted in the complete paper. Introduction The XamXung field was discovered in 1967, with commercial production established in 1972. The field is a simple faulted anticline bounded by two major faults in the north and south. The field consists primarily of clastic deposits characterized by thick sands interbedded with thin shale layers of late Miocene to Pliocene age. The field consists of multiple stacked gas and oil reservoirs, with key producing intervals being the oil-rim reservoirs XE/XF and XH/XI, and the deeper oil reservoir XL, as well as major nonassociated gas reservoirs XA, XC, XD, XM, and XN. The main discussion of the complete paper focuses on XE/XF and XH/XI reservoir redevelopment. XE/XF is a saturated oil-rim reservoir with initial oil-rim thicknesses of 95 and 85 ft, respectively. The XE/XF oil rim is overlain by a gas cap with m size (ratio of initial free-gas reservoir volume to initial reservoir oil volume) of 1.1 and 0.4, respectively. XE and XF reservoirs are separated by a fieldwide sealed shale layer of 10–20-ft thickness. Initial reservoir pressure and well log data acquired during the early production his-tory suggested that XE/XF reservoirs originally shared a common gas/oil con-tact (GOC) but different free-water levels. XE/XF reservoirs have an average porosity of 27–32% and average permeability of 500–1500 md. They started production in 1974 and reached peak production in 1977. The reservoir pressure has declined by only 200 psi after 45 years of production, indicating that the reservoir is under a strong aquifer drive. Gas injection into XE reservoir commenced in 1995 following an increasing water-cut trend in most of the producers, with the objective to counteract the aquifer influx and to allow uniform gas-cap gas expansion throughout the reservoir. However, the reservoir historically has produced more free gas compared with the amount of gas reinjected, resulting in the reservoir gas-cap shrinkage.

Natural Wool for Removal of Oil Spills from Water Surface

Romanian Merino wool was tested as a natural sorbent for oil spill cleanup. Rebco crude oil placed in distilled water was used as an oily water model. Experiments of batch sorption were performed under various conditions. The effects of process factors, i.e., initial density of packed bed sorbent (0.05-0.99 g/cm3), initial volume ratio of oil and water (0.25 and 0.14 cm3/cm3), and contact surface between adsorbent and oily water, on wool sorption capacity (6.4-11.8 g/g) were evaluated. Experimental data were fitted using pseudo-first order rate and pseudo-second order rate models.

Natural Wool for Removal of Oil Spills from Water Surface

Romanian Merino wool was tested as a natural sorbent for oil spill cleanup. Rebco crude oil placed in distilled water was used as an oily water model. Experiments of batch sorption were performed under various conditions. The effects of process factors, i.e., initial density of packed bed sorbent (0.05-0.99 g/cm3), initial volume ratio of oil and water (0.25 and 0.14 cm3/cm3), and contact surface between adsorbent and oily water, on wool sorption capacity (6.4-11.8 g/g) were evaluated. Experimental data were fitted using pseudo-first order rate and pseudo-second order rate models. Keywords: oil spill, kinetic model, sorption capacity, wool fibre

Obstetric and neonatal outcomes in pregnancies complicated by fetal lung masses: does final histology matter?#

Purpose Fetal lung masses complicate approximately 1 in 2000 live births. Our aim was to determine whether obstetric and neonatal outcomes differ by final fetal lung mass histology. Materials and methods A review of all pregnancies complicated by a prenatally diagnosed fetal lung mass between 2009 and 2017 at a single academic center was conducted. All cases included in the final analysis underwent surgical resection and histology diagnosis was determined by a trained pathologist. Clinical data were obtained from review of stored electronic medical records which contained linked maternal and neonatal records. Imaging records included both prenatal ultrasound and magnetic resonance imaging. Fisher’s exact test was used for categorical variables and the Kruskal–Wallis test was used for continuous variables. The level of significance was p<.05. Results Of 61 pregnancies complicated by fetal lung mass during the study period, 45 cases underwent both prenatal care and postnatal resection. Final histology revealed 10 cases of congenital pulmonary airway malformation (CPAM) type 1, nine cases of CPAM type 2, and 16 cases of bronchopulmonary sequestration. There was no difference in initial, maximal, or final CPAM volume ratio between groups, with median final CPAM volume ratio of 0.6 for CPAM type 1, 0.7 for CPAM type 2, and 0.3 for bronchopulmonary sequestration (p = .12). There were no differences in any of the maternal or obstetric outcomes including gestational age at delivery and mode of delivery between the groups. The primary outcome of neonatal respiratory distress was not statistically different between groups (p = .66). Median neonatal length of stay following delivery ranged from 3 to 4 days, and time to postnatal resection was similar as well, with a median of 126 days for CPAM type 1, 122 days for CPAM type 2, and 132 days for bronchopulmonary sequestration (p = .76). Conclusions In our cohort, there was no significant association between histologic lung mass subtypes and any obstetric or neonatal morbidity including respiratory distress.

A new application area of electrochemical limiting diffusion current technique: measurement of mixing time and effect of some parameters

In this study, the electrochemical limiting diffusion current technique, which was employed first time for the mixing time measurement in the stirred tank system by the authors, was applied to determine the effect of some parameters on the global and local mixing times in the range of 3500 ≤ Re ≤ 10,000. The technique well sensed that increasing Reynolds number (Re), blade angle and blade number decreased the mixing time. The most effective parameter was observed to be Re, and the blade number and blade angle, in order. In addition, the mixing time was also investigated for solutions added in various volume fractions having different viscosity and density by using local mixing time measurement. It was determined that the mixing time decreased with the Reynolds number, the ratio of the initial solution volume to the total solution volume and the ratio of kinematic viscosity of the solution in the vessel initially to that of the added one viscosity. The ratio of initial solution volume to total solution volume was found to be a more effective parameter than the others in terms of mixing time.

Experimental study on the deflagration characteristics of methane-ethane mixtures in a closed duct

For the study of premixed methane/ethane/air explosion propagation characteristics, the explosion overpressure parameters and flame propagation process images of premixed methane/ethane at different initial stoichiometric and volume ratios were obtained by using a horizontal closed duct and a high-speed camera. The numerical simulation method was used to study the evolution characteristics of the flow field inside the duct during explosion propagation. Parameters such as the maximum explosion pressure (Pmax), maximum pressure rise rate (dP/dt)max and combustion time tc of the premixed system were acquired. The premixed system flame front position was detected based on a self-written program of the Canny operator, and the variations in the premixed flame propagation speed were obtained. The results show that with increasing ethane volume fraction, the premixed system explosion process is more rapid and drastic. Each premixed system can be divided into three combustion stages according to the different ethane volume fractions: the methane-dominant combustion stage (I), transition stage (II) and ethane-dominant combustion stage (III). When a tulip flame is generated, a vortex is created inside the duct. After a plane flame is formed by the flame front, the pressure rise rate (dp/dt) sharply oscillates. Based on the GRI-Mech3.0 mechanism, the chemical kinetics analysis of the premixed gas showed that the production rate of key free radicals (H*,O* and OH*) gradually increased with the increase of ethane volume fraction, thus enhancing the explosion reaction intensity.

Janus emulsions formed with organic solvents as inner phases

Organic solvents are used as oil phases to prepare oil in water Janus emulsions by one-step vortex mixing. The categories of organic solvents cover alkanes, cycloalkanes, aromatics, alcohols and esters. Micrograph images show the well-defined Janus morphology composed by organic solvents and the corresponding immiscible oils. Topologies of “snowman”, “dumbbell” and “perfect Janus” are obtained, which depends on the category of organics. It is worth mention that two different topologies are obtained in one system, which is mainly determined by the density difference of two inner phases. In addition, the adjustment of oil/oil interface curvature is achieved by changing the surfactant concentration and also by the initial volume ratio of two inner phases. Moreover, the droplet size decreased significantly, from hundreds of micrometers continuously down to several micrometers is realized and more importantly, the topology of Janus droplets remains. The reported organic Janus emulsions with droplets constructed by two separated domains and sharp domain boundary would be ideal microreactors, templates for materials synthesis.

Empirical investigation of friction weakening of terrestrial and Martian landslides using discrete element models

Understanding what controls the travelling distance of large landslides has been the topic of considerable debate. By combining observation and experimental data with depth-averaged continuum modelling of landslides and generated seismic waves, it was empirically observed that lower effective friction had to be taken into account in the models to reproduce the dynamics and runout distance of larger volume landslides. Moreover, such simulation and observation results are compatible with a friction weakening with velocity as observed in earthquake mechanics. We investigate here as to whether similar empirical reduced friction should be put into discrete element models (DEM) to reproduce observed runout of large landslides on Earth and on Mars. First we show that, in the investigated parameter range and for a given volume, the runout distance simulated by 3D DEM is not much affected by the number (i.e. size) of grains once this number attains ~ 8000. We then calibrate the model on laboratory experiments and simulate other experiments of granular flows on inclined planes, making it possible for the first time to reproduce the observed effect of initial volume and aspect ratio on runout distances. In particular, the normalised runout distance starts to depend on the volume involved only above a critical slope angle > 16–19°, as observed experimentally. Finally, based on field data (volume, topography, deposit), we simulate a series of landslides on simplified inclined topography. The empirical friction coefficient, calibrated to reproduce the observed runout for each landslide, is shown to decrease with increasing landslide volume (or velocity), going down to values as low as 0.1–0.2. No distinguishable difference is observed between the behaviour of terrestrial and Martian landslides.

Preparation and characterization of microemulsion fuels from diesel and model compound of walnut shell pyrolysis oil

In this study, a bio-oil model compound of walnut shell pyrolysis oil was selected. The microemulsions of diesel and model compound were produced using Span80 and Tween 80 as surfactants. The microemulsions were quantificationally analyzed to investigate the solubilization capacity of bio-oil characteristic components in diesel. The effects of surfactant concentration and initial volume ratio of bio-oil model compound to diesel (B/D ratio) on the solubilization capacity of bio-oil characteristic components in diesel were investigated. The heating value, kinematic viscosity, elemental analysis and thermogravimetric analysis of microemulsion were also conducted. Experimental results indicated that the suitable concentration of surfactant was 0.3 mol/L–0.45 mol/L, and the optimum B/D ratio was 4:12 for the bio-oil model compound. The dissolubility of m-cresol and guaiacol in microemulsion was much better than that of water and acetic acid. The heating value and the kinematic viscosity of microemulsion decreased slightly as the B/D ratio increased. Increasing the surfactant concentration contributed to a more pronounced increase in the kinetic viscosity and a significant decrease in the heating value. The influence of surfactant concentration on the fuel properties and thermogravimetric characteristics was stronger than that of B/D ratio.

Flight performance simulation and station-keeping endurance analysis for stratospheric super-pressure balloon in real wind field

For the absence of the propeller system to resist wind load, the balloon will float everywhere with unstable position. In order to fix the balloon within a specific district and extend the station-keeping endurance, an effective approach that utilizes the wind from different directions by altering the float altitude was proposed. A program was developed to simulate the flight performance and the station-keeping endurance of the stratospheric super-pressure balloon in the real wind field. The influences of the initial Helium volume ratio and the float altitude on the traveled horizontal distance of the balloon were analyzed. The results indicate that the altitude of the balloon fluctuates with the change of the volume of the balloon during the day-night cycle, providing the possibility to catch the wind from different directions. By choosing the appropriate Helium volume ratio and float altitude, the traveled horizontal distance of the balloon can be shortened greatly. Our study can provide guidance for investigation on active control algorithm for station-keeping of the balloon that can fix the balloon within the desired district for months and years.

Bipolar membrane electrodialysis for the recycling of ammonium chloride wastewater: Membrane selection and process optimization

Here, bipolar membrane electrodialysis (BMED) with BP-A configuration is employed to convert ammonium chloride wastewater into hydrochloric acid and ammonium hydroxide to overcome the shortcomings of conventional treatment methods First, different commercial anion exchange membranes (TWEDA2, AMV, JAM-II and CJMA-2) and bipolar membranes (BP-1, BPM-I and FBM) were used to conduct the BMED process. Results show that AMV and BPM-I are regarded as the optimum membranes in consideration of process performance, energy consumption and process cost comprehensively. Second, BMED process is optimized by changing current density, initial NH4Cl concentration and initial volume ratio of acid solution and NH4Cl solution. Results indicate that as current density increases from 70 to 90mA/cm2, energy consumption and generated HCl concentration can increase from 1.51 to 2.83 kWh/kg HCl and 2.45 to 2.84mol/L respectively, and the total process cost of 70mA/cm2 is the highest (0.80$/kg HCl); meanwhile, increasing initial NH4Cl concentration can increase energy consumption, generated acid concentration and total process cost; in addition, with the increment of initial volume ratio from 0.5 to 1.0, energy consumption varies between 1.46 and 1.62 kWh/kg HCl and generated acid concentration improves from 1.95 to 2.71mol/L, while total process cost decreases from 0.63 to 0.42$/kg HCl. In short, based on these results, the optimum operation condition is that current density is 80mA/cm2, initial NH4Cl concentration is 1mol/L and initial volume ratio of acid solution and NH4Cl solution is 0.67–0.83.