Numerous laboratory experiments and field cases show that even very small amount of oil in injected water can cause severe injectivity damage. Although injectivity decline caused by oil droplets has been studied exper...Numerous laboratory experiments and field cases show that even very small amount of oil in injected water can cause severe injectivity damage. Although injectivity decline caused by oil droplets has been studied experimentally, there is still lack of an easy-to-use and widely accepted model to predict the decline behavior. In this work, we developed an analytical model to predict the time-dependent progress of the water permeability reduction in linear flow by analyzing experimental data obtained from linear core flooding. The model considers mass transfer of the oil phase from the produced water to the rock due capture effects by dispersion, advection and adsorption inside the rock. As the captured oil saturation increases, permeability reduces following the relative permeability drainage relationship. The reduction stabilizes when the oil saturation comes to an equilibrium value controlled by oil droplet size and injection velocity. The model is calibrated using published experimental data from prolonged core floods with oil- contaminated waste water. Theoretical runs of the model replicate all the effects known from experimental observations. Resulting from the model is a distributed change of permeability vs. time and distance from the point of injection that can be converted to the overall injectivity damage.展开更多
Foam is utilized in enhanced oil recovery and CO_(2) sequestration.Surfactant-alternating-gas(SAG)is a preferred approach for placing foam into reservoirs,due to it enhances gas injection and minimizes corrosion in fa...Foam is utilized in enhanced oil recovery and CO_(2) sequestration.Surfactant-alternating-gas(SAG)is a preferred approach for placing foam into reservoirs,due to it enhances gas injection and minimizes corrosion in facilities.Our previous studies with similar permeability cores show that during SAG injection,several banks occupy the area near the well where fluid exhibits distinct behaviour.However,underground reservoirs are heterogeneous,often layered.It is crucial to understand the effect of permeability on fluid behaviour and injectivity in a SAG process.In this work,coreflood experiments are conducted in cores with permeabilities ranging from 16 to 2300 mD.We observe the same sequence of banks in cores with different permeabilities.However,the speed at which banks propagate and their overall mobility can vary depending on permeability.At higher permeabilities,the gas-dissolution bank and the forced-imbibition bank progress more rapidly during liquid injection.The total mobilities of both banks decrease with permeability.By utilizing a bank-propagation model,we scale up our experimental findings and compare them to results obtained using the Peaceman equation.Our findings reveal that the liquid injectivity in a SAG foam process is misestimated by conventional simulators based on the Peaceman equation.The lower the formation permeability,the greater the error.展开更多
In this note,some characterizations of hereditary rings using injectivity classes and projectivity classes are given.These results unify many well known results.
With increasing CO_(2)concentration in the atmosphere,CO_(2)geo-aequestration has become a popular technique to counter the dangers of global warming resulting from high levels of CO_(2)in the atmosphere.This paper ex...With increasing CO_(2)concentration in the atmosphere,CO_(2)geo-aequestration has become a popular technique to counter the dangers of global warming resulting from high levels of CO_(2)in the atmosphere.This paper examins sequestration parameters such as CO_(2)plume behaviour,residual gas trapping and injectivity as a means of achieving safe and successful CO_(2)storage in saline aquifers.Mineral precipitation/dissolution rates are used to establish a relationship between these parameters and geochemical reactions in saline aquifers.To achieve this,mechanistic models(6 models with different inputs,created using CMG e GEM,2016 and WINPROP,2016)are simulated using input data from literature and studying changes in fluids and formation properties as well as mineral precipitation/dissolution rates in aquifers when subjected to different conditions in the different models.The results from the models show that high CO_(2)dissolution,which creates large CO_(2)plume,leads to high mineral dissolution/precipitation as results of increased fluid-rock interactions(geochemical reactions);whereas injectivity,although enhanced by CO_(2)-water cyclic injection,does not show much increase in bottom hole pressure when mineral trapping(thus geochemical reactions)is introduced into the model.Sensitivity study on residual gas trapping shows that high residual gas saturation leads to reduced mineral precipitation/dissolution due to the reduced amount of dissolved CO_(2)in brine.Also,rapid changes in the bottom hole pressure at high residual gas saturation means that a formation that fosters high residual gas trapping,rather than CO_(2)dissolution in brine,is more likely to experience injectivity issues during the sequestration process.展开更多
The attenuation of CO_(2)injectivity has become the biggest technical barrier for the application of CO_(2)enhanced coalbed methane recovery(CO_(2)-ECBM).Commonly,the intermittent CO_(2)injection,N2 displacing CO_(2)a...The attenuation of CO_(2)injectivity has become the biggest technical barrier for the application of CO_(2)enhanced coalbed methane recovery(CO_(2)-ECBM).Commonly,the intermittent CO_(2)injection,N2 displacing CO_(2)and pre-fracturing are the potential CO_(2)enhanced injectivity methods for coal reservoirs,but their mechanism and effectiveness remain to be clarified.This paper thus conducted small-scale experiments to simulate the working process of these engineering measures by an independently developed experimental device.Results show that the CO_(2)injectivity of coal is remarkably improved by the intermittent injection mode since the CO_(2)injection time is increased by folds and the loss of reservoir pressure can be complemented in time.The N_(2)displacing CO_(2)method promotes the desorption of CO_(2)and reduces the swelling strain,with the result that the permeability of coal is improved by 74.82%and 64.95%compared with the methods of the primary subcritical CO_(2)(Sub CO_(2))and supercritical CO_(2)(Sc CO_(2))injection.However,the permeability reduces again with the secondary CO_(2)injection.The permeability of the coal sample after pre-fracturing is averagely improved by 1-2 orders of magnitude,the irreversible permeability loss rate,average stress sensitivity coefficient and the permeability loss rate due to adsorption are averagely reduced by 95.885%,61.538%and 96.297%,respectively.This indicates that the permeability of coal after pre-fracturing is no longer sensitive to both the effective stress and Sc CO_(2)adsorption,the injectivity is thus improved and stable.The CO_(2)enhanced injectivity effects of the intermittent CO_(2)injection,the N_(2)displacing CO_(2)and the pre-fracturing are various,which thus can be selected individually or jointly to improve the CO_(2)injectivity according to the reservoir physical properties and geological conditions.This research deepens the understanding of the functional mechanism of CO_(2)enhanced injectivity methods and provides some guidance for their selection and application in engineering practices.展开更多
Well injectivity decline during waterflooding is primarily attributed to retention of injected particles within pores,subsequently blocking flow channels in near-wellbore regions.Developing a predictive model to descr...Well injectivity decline during waterflooding is primarily attributed to retention of injected particles within pores,subsequently blocking flow channels in near-wellbore regions.Developing a predictive model to describe this problem holds significant value as it can inform the development of strategies aimed at preventing or mitigating such damage.Previous research has typically assumed a linear suspension flow or a constant filtration coefficient,which does not represent the near-wellbore suspension flow very well.In this paper,an analytical model for the radial suspension transport in porous media is derived based on the Langmuirian blocking filtration mechanism.Considering the dimensionless distance from the wellbore as a small parameter,we attain the analytical solution through an asymptotic expansion.To provide a basis for comparison,we also obtain numerical solutions using Shampine's code,which is based on the explicit central finite difference method.Comparison of the analytical and numerical solutions shows that their difference errors remain below 5%under waterflooding conditions.Based on the analytical solution for retained particle concentration,expressions for injection pressure,damage factor and damaged zone radius are also derived and are also expressed explicitly.In the end,we discuss two practical applications of our model:evaluation of existing acidizing jobs and designing new acidizing jobs,based on real field data from Tarim Basin,western China.The results indicate our model is practical in field operations.展开更多
We consider an associated Riemannian metric induced by a rigging defined on a neighborhood of the null hypersurface in a Lorentzian manifold,and we connect this null geometry with the associated Riemannian geometry.Us...We consider an associated Riemannian metric induced by a rigging defined on a neighborhood of the null hypersurface in a Lorentzian manifold,and we connect this null geometry with the associated Riemannian geometry.Using a rigging defined on some open set containing the lightlike hypersurface,we introduce a global geometric invariant Rad^(ζ)(M)related to injectivity radius to a closed complete noncompact null hypersurface in a Lorentzian manifold.Using some comparison theorems from non-degenerated geometry,we give the relationship between geometry and topology of a closed complete noncompact null hypersurface with associated Riemannian metric and the asymptotic properties of injectivity radiuses at infinity.展开更多
For a commtative ring R and an injective cogenerator E in the category of R-modules, we characterize QF rings, IF rings and semihereditary rings by using the properties of the dual modules with respect to E.
A right R-module E over a ring R is said to be maximally injective in case for any maximal right ideal m of R, every R-homomorphism f ： m → E can be extended to an R-homomorphism f^1 ： R → E. In this paper, we fir...A right R-module E over a ring R is said to be maximally injective in case for any maximal right ideal m of R, every R-homomorphism f ： m → E can be extended to an R-homomorphism f^1 ： R → E. In this paper, we first construct an example to show that maximal injectivity is a proper generalization of injectivity. Then we prove that any right R-module over a left perfect ring R is maximally injective if and only if it is injective. We also give a partial affirmative answer to Faith＇s conjecture by further investigating the property of maximally injective rings. Finally, we get an approximation to Faith＇s conjecture, which asserts that every injective right R-module over any left perfect right self-injective ring R is the injective hull of a projective submodule.展开更多
Regarding the enormous demands of numerous industries to fossil fuels,it is essential to select the proper enhanced oil recovery approaches for vertical and horizontal wells to supply the demands with the optimum expe...Regarding the enormous demands of numerous industries to fossil fuels,it is essential to select the proper enhanced oil recovery approaches for vertical and horizontal wells to supply the demands with the optimum expenditure.Water and gas injectivity as the secondary enhanced oil recovery techniques would be preferentially considered regarding their low costs of performances rather than chemical recovery and thermal techniques.Injected gas tends to push oil through pores or cracks in the matrix block and lead them to the production well.Therefore,injection of gas may significantly increase the recovery factor in these reservoirs.In this research,different injection scenarios in a fractured carbonate reservoir in the west of Iran are being simulated by the PVT modules of Eclipse software.The purpose of this research is to analyze the possibility of gradually increasing the extent of recovery by injecting carbon dioxide,methane,and water,and different injectivity patterns are considered in this research.The selection of injectivity patterns is severely based on the highest recycling rate of gas injection on different injection scenarios,and the injectivity scenarios were being compared with the natural depletion scenario.Consequently,Co2 injection(about 60%)had the highest oil recovery factor and CH4 and TB(about 54%and 53%)injectivity scenarios had the second and third highest rate of the oil recovery factor.展开更多
Depleted gas reservoirs are used for a large-scale carbon dioxide(CO_(2))storage and reduction of the greenhouse gas released into the atmosphere.To identify a suitable depleted reservoir,it is essential to do a preli...Depleted gas reservoirs are used for a large-scale carbon dioxide(CO_(2))storage and reduction of the greenhouse gas released into the atmosphere.To identify a suitable depleted reservoir,it is essential to do a preliminary and comprehensive assessment of key storage factors such as storage capacity,injectivity,trapping mechanisms,and containment.However,there are a limited number of studies providing a preliminary assessment of CO_(2) injectivity potential in depleted gas reservoirs prior to a CO_(2) storage operation.The aim of this study is to provide a preliminary assessment of a gas field located in Malaysia for its storage potential based on subsurface characterization prior to injection.Evaluation of the reservoir interval based on the facies,cores,and wireline log data of a well located in the field indicated that the pore type and fabrics analysis is very beneficial to identify suitable locations for a successful storage practice.Although the results obtained are promising,it is recommended to combine this preliminary assessment with the fluid-mineral interactions analysis before making any judgment about reliability of storage sites.展开更多
With its growth in spacecraft control applications,the microcontroller(MCU)becomes increasingly sensitive to radiation and the risks of system failure.In a radiation environment,the MCU is vulnerable to impacts from h...With its growth in spacecraft control applications,the microcontroller(MCU)becomes increasingly sensitive to radiation and the risks of system failure.In a radiation environment,the MCU is vulnerable to impacts from high-energy particles,which can lead to single-event effect(SEE)that disrupt normal system operations.The pipeline of MCU,being the core structure of the system,is particularly susceptible to single-event upset(SEU)and potentially causes execution failures.However,existing radiation-hardening techniques offer limited effectiveness for pipelines.To enhance SEU resistance,this study focused on a 32-bit MCU core with eight pipeline stages,proposing a pipeline hardening approach that utilizes lockstep technology to improve fault tolerance.Signals from two processors were compared including register write data,register contents and pre-fetched instructions.Any discrepancies triggered error flags to indicate faults.When an error flag was raised,recovery was initiated through an interrupt.The interrupt handler then retrieved state information from the advanced peripheral bus(APB)slave module to restore the CPU's operational state and resume execution.By combining hardware-based state preservation with software-driven error recovery,the proposed solution demonstrated significant improvements in fault tolerance rates and performance compared to traditional checkpoint-based techniques.After completing the pipeline hardening design,a fault injection platform was utilized in this paper to simulate real-world error conditions on internal processor modules.The platform was developed based on the circuit's register-transfer-level(RTL)design and statistical results.The fault injection platform was performed by automatically finding all registers within the target design.The register values were forced to upset at the tens of nanoseconds scale in the RTL description of the circuit's design.After running the circuit's functional simulation,the statistics of the faults in registers were displayed on the platform,which evaluated the influence of SEU.The vulnerability of SEU in the circuit could be observed from the results of the soft error statistics.The post-hardening soft error rates were then measured and compared to pre-hardening data,providing a quantitative evaluation of the improvements.Using this method,the soft error rates of the modules in the MCU core such as PFU,DPU,and Cache AXIM are 40.07%,26.36%,and 27.29%respectively before hardening.The soft error rates of modules mentioned above are reduced to 0%,0.69%,and 1.11%after hardening.The hardened and non-hardened designs of the entire core were implemented in FPGA.The total resource utilization of the triple mode redundancy(TMR)is 111984,as indicated by the number of look-up tables(LUTs)and registers consumed in the FPGA.The total resource utilization of this work is 78034,and the ratio of resource utilization between this work and TMR is approximately 69.68%.The error recovery time for the hardened MCU processor was analyzed using the completion cycles of a bubble sort algorithm as a benchmark.In this paper,the average recovery cycle using the software checkpoint roll-back method is 36479.06,and the average recovery cycle using this work is 26922.5.The ratio of recovery cycles between this work and checkpoint roll-back is about 73.8%.Assessments through random fault injection and FPGA implementation indicate that this approach effectively reduces processor faults caused by soft errors while optimizing resource utilization and efficiency over triplemodular redundancy.展开更多
We use analytic methods in this paper to prove some new Enoki type injeetivity theorems on compact complex manifolds which generalize more or less the original Enoki injectivity theorem.
We study the injectivity radius bound for 3-d Ricci flow with bounded curvature. As applications, we show the long time existence of the Ricci flow with positive Ricci curvature and with curvature decay condition at i...We study the injectivity radius bound for 3-d Ricci flow with bounded curvature. As applications, we show the long time existence of the Ricci flow with positive Ricci curvature and with curvature decay condition at infinity. We partially settle a question of Chow-Lu-Ni [Hamilton＇s Ricci Flow, p. 302].展开更多
BACKGROUND The previous studies have primarily focused on the influence of botulinum toxin A(BoNT-A)injection on emotions during the period of peak motor symptom improvement in blepharospasm patients,based on facial f...BACKGROUND The previous studies have primarily focused on the influence of botulinum toxin A(BoNT-A)injection on emotions during the period of peak motor symptom improvement in blepharospasm patients,based on facial feedback hypothesis.AIM To evaluate the sustained anxiolytic and antidepressant effects of BoNT-A in blepharospasm patients beyond motor symptom control.METHODS We recruited benign essential blepharospasm patients with BoNT-A treatment and collected their data to compare scale scores of Jankovic Rating Scale,Blepharospasm Disability Index,Self-rating Anxiety Scale(SAS),Self-rating Depression Scale(SDS),Hamilton Anxiety Scale and Hamilton Depression Scale between pretreatment(baseline)and pre-reinjection(treatment),to further assess the effects of repeated treatments with BoNT by using sub-group analyses in the certain special states.RESULTS A total of 21 eligible blepharospasm patients were with the mean age of 58.4 years and a male-to-female ratio of 1:6.Significantly decreases in the subscale scores of SDS and SAS,including SDS well-being index,decreased capacity and hard to decide,SAS inability to sit still and headache were showed at post-a single BoNT-A injection when scale scores of Jankovic Rating Scale and Blepharospasm Disability Index were matched between baseline and posttreatment.With each additional BoNT-A injection,the odds ratio of patients with the moderate depressive symptoms decreased by 92.6%.Moreover,BoNT treatment remained a decrease in the subscale scores of SDS and SAS in patients with repeated injections.CONCLUSION This study is to demonstrate that repeated BoNT-A injection have a long-lasting relief for anxiety and depressive symptoms in blepharospasm even after its motor symptom-modulating effects have diminished.展开更多
Early knee osteoarthritis(KOA)is characterized by progressive degeneration of the articular cartilage,synovial inflammation,and excessive accumulation of reactive oxygen species(ROS).At present,intra-articular injecti...Early knee osteoarthritis(KOA)is characterized by progressive degeneration of the articular cartilage,synovial inflammation,and excessive accumulation of reactive oxygen species(ROS).At present,intra-articular injection of hyaluronic acid(HA)is widely used to alleviate symptoms;however,its lubrication persistence,antioxidant,and anti-inflammatory abilities are limited,and it is difficult to effectively delay the early process of cartilage degeneration.Based on this,hyaluronic acid-g-lipoic acid(HA-LA)was synthesized by esterification reaction,and HA-LA microspheres were prepared by a reversed-phase emulsion method,which was combined with a macromolecular HA-LA solution to form injectable hydrogels.The objective of this study was to evaluate the efficacy of an injectable hydrogel based on hyaluronic acid-g-lipoic acid microspheres(HA-LA MS)for the treatment of KOA and to verify its injectability,lubricity,reactive oxygen species(ROS)scavenging ability,and anti-inflammatory effects.The results show that the HA-LA MS hydrogel has excellent shear thinning characteristics and continuous injectability,and its microsphere structure significantly reduces the interfacial friction coefficient through the rolling effect.In vitro experiments have shown that the hydrogel can efficiently scavenge ROS,reduce the expression of inflammatory factors,and is non-cytotoxic.The HA-LA MS injectable hydrogel has excellent lubricity,ROS scavenging ability,and anti-inflammatory effects in vivo,which can effectively delay the degeneration of early KOA cartilage,and its efficacy is significantly better than that of traditional hyaluronic acid,making it a promising intra-articular injection preparation.展开更多
Objective:To compare the clinical efficacy and safety of intravitreal injection of faricimab and conbercept in the treatment of diabetic macular edema(DME).Methods:A total of 50 patients diagnosed with DME in our hosp...Objective:To compare the clinical efficacy and safety of intravitreal injection of faricimab and conbercept in the treatment of diabetic macular edema(DME).Methods:A total of 50 patients diagnosed with DME in our hospital from January 2023 to May 2025 were selected and randomly divided into an observation group and a control group,with 25 cases in each group,using a random number table method.The observation group received intravitreal injection of faricimab,while the control group received intravitreal injection of conbercept.Both groups adopted a loading phase plus maintenance phase treatment regimen.The best-corrected visual acuity(BCVA,expressed in logMAR)and central subfield thickness(CST)of the two groups were compared before treatment and at 1,3,and 6 months after treatment,and the incidence of adverse events during treatment was recorded.Results:The logMAR BCVA in the observation group was lower than that in the control group at 3 and 6 months after treatment(both p<0.05).The CST in the observation group was smaller than that in the control group at 1,3,and 6 months after treatment(all p<0.05).There was no statistically significant difference in the overall incidence of adverse events between the two groups(χ^(2)=0.189,p=0.663).Conclusion:Both intravitreal injections of faricimab and conbercept are effective in improving visual acuity and reducing macular edema in patients with DME,with good safety profiles.However,faricimab demonstrates superior efficacy in the medium to long term(3 and 6 months)compared to conbercept,making it more suitable for long-term treatment of patients with DME.展开更多
In this paper,we study two types of the Ding injective dimensions of complexes.First,we provide some equivalent characterizations of the dimension related to the special Ding injec-tive preenvelopes.Furthermore,we con...In this paper,we study two types of the Ding injective dimensions of complexes.First,we provide some equivalent characterizations of the dimension related to the special Ding injec-tive preenvelopes.Furthermore,we consider the relationship between the dimensions Dipd(Y)and Did(Y)of the complex Y,where Dipd(Y)denotes the dimension associated with special Ding injective preenvelopes,and Did(Y)denotes the dimension associated with DG-injective resolutions.It is demonstrated that Dipd(Y)=Did(Y)for any bounded complex Y.展开更多
To address the kinetic constraints inherent in the catalytic combustion of pulverized coal injection under low heating-rate conditions within conventional air atmospheres,a drop tube furnace was utilized to simulate t...To address the kinetic constraints inherent in the catalytic combustion of pulverized coal injection under low heating-rate conditions within conventional air atmospheres,a drop tube furnace was utilized to simulate the catalytic combustion of pulverized coal(PC).The effects of gas composition,oxygen concentration,the type,and the content of catalysts on the combustion reactivity were systematically analyzed.Furthermore,the structural changes of unburned pulverized coal were also examined.Experimental results indicate that as the oxygen concentration increased from 21%to 79%,compared with the O_(2)/N_(2)condition,the increment in the burnout rate of PC under the O_(2)/CO_(2)condition increased from 3%to 23%.After the addition of catalysts,including hematite,metallurgical oil sludge,and light-burnt dolomite(LBD),under the condition of 21%oxygen concentration,the effects of the three catalysts under the O_(2)/CO_(2)condition were superior to those under the O_(2)/N_(2)condition.This trend was reversed under the conditions of 38%and 79%oxygen concentrations.In all atmospheres,the three catalysts can enhance the burnout rate of PC.Among them,LBD exhibits the most favorable effect,and there exists an optimal dosage.Mechanistic analysis through scanning electron microscopy,X-ray diffraction,and N_(2)adsorption-desorption reveals that under 21%O_(2)/79%CO_(2)conditions,high-concentration CO_(2)leads to the formation of pores,and additives accelerate the oxidation of C and the gasification of CO_(2)through oxygen transfer,thereby enhancing the burnout rate of PC.展开更多
基金part of a research program, Downhole Water Sink Technology Initiative (DWSTI) ―a Joint Industry Project (JIP) at LSU
文摘Numerous laboratory experiments and field cases show that even very small amount of oil in injected water can cause severe injectivity damage. Although injectivity decline caused by oil droplets has been studied experimentally, there is still lack of an easy-to-use and widely accepted model to predict the decline behavior. In this work, we developed an analytical model to predict the time-dependent progress of the water permeability reduction in linear flow by analyzing experimental data obtained from linear core flooding. The model considers mass transfer of the oil phase from the produced water to the rock due capture effects by dispersion, advection and adsorption inside the rock. As the captured oil saturation increases, permeability reduces following the relative permeability drainage relationship. The reduction stabilizes when the oil saturation comes to an equilibrium value controlled by oil droplet size and injection velocity. The model is calibrated using published experimental data from prolonged core floods with oil- contaminated waste water. Theoretical runs of the model replicate all the effects known from experimental observations. Resulting from the model is a distributed change of permeability vs. time and distance from the point of injection that can be converted to the overall injectivity damage.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.U2240210,52279098)the Natural Science Foundation of Jiangsu Province(Grant No.BK20200525)the Fundamental Research Funds for the Central Universities(Grant No.B230201021).We express our gratitude to PETRONAS and Shell Global Solution International B.V.for their support of this work.
文摘Foam is utilized in enhanced oil recovery and CO_(2) sequestration.Surfactant-alternating-gas(SAG)is a preferred approach for placing foam into reservoirs,due to it enhances gas injection and minimizes corrosion in facilities.Our previous studies with similar permeability cores show that during SAG injection,several banks occupy the area near the well where fluid exhibits distinct behaviour.However,underground reservoirs are heterogeneous,often layered.It is crucial to understand the effect of permeability on fluid behaviour and injectivity in a SAG process.In this work,coreflood experiments are conducted in cores with permeabilities ranging from 16 to 2300 mD.We observe the same sequence of banks in cores with different permeabilities.However,the speed at which banks propagate and their overall mobility can vary depending on permeability.At higher permeabilities,the gas-dissolution bank and the forced-imbibition bank progress more rapidly during liquid injection.The total mobilities of both banks decrease with permeability.By utilizing a bank-propagation model,we scale up our experimental findings and compare them to results obtained using the Peaceman equation.Our findings reveal that the liquid injectivity in a SAG foam process is misestimated by conventional simulators based on the Peaceman equation.The lower the formation permeability,the greater the error.
文摘In this note,some characterizations of hereditary rings using injectivity classes and projectivity classes are given.These results unify many well known results.
文摘With increasing CO_(2)concentration in the atmosphere,CO_(2)geo-aequestration has become a popular technique to counter the dangers of global warming resulting from high levels of CO_(2)in the atmosphere.This paper examins sequestration parameters such as CO_(2)plume behaviour,residual gas trapping and injectivity as a means of achieving safe and successful CO_(2)storage in saline aquifers.Mineral precipitation/dissolution rates are used to establish a relationship between these parameters and geochemical reactions in saline aquifers.To achieve this,mechanistic models(6 models with different inputs,created using CMG e GEM,2016 and WINPROP,2016)are simulated using input data from literature and studying changes in fluids and formation properties as well as mineral precipitation/dissolution rates in aquifers when subjected to different conditions in the different models.The results from the models show that high CO_(2)dissolution,which creates large CO_(2)plume,leads to high mineral dissolution/precipitation as results of increased fluid-rock interactions(geochemical reactions);whereas injectivity,although enhanced by CO_(2)-water cyclic injection,does not show much increase in bottom hole pressure when mineral trapping(thus geochemical reactions)is introduced into the model.Sensitivity study on residual gas trapping shows that high residual gas saturation leads to reduced mineral precipitation/dissolution due to the reduced amount of dissolved CO_(2)in brine.Also,rapid changes in the bottom hole pressure at high residual gas saturation means that a formation that fosters high residual gas trapping,rather than CO_(2)dissolution in brine,is more likely to experience injectivity issues during the sequestration process.
基金sponsored by the National Natural Science Foundation of China(Grant nos.41727801,41972281,51979170,11902208,U1967208 and 41330638)the National Key Research and Development Plan Project of China(2018YFB0605600)+2 种基金the Natural Science Foundation of Hebei Province(E2021210077)the Autonomous subject of State Key Laboratory of Mechanical Behavior and System Safety of Traffic Engineering Structures(ZZ2020-29)Science and Technology Research Project of Hebei Province Colleges and Universities(QN2021129)。
文摘The attenuation of CO_(2)injectivity has become the biggest technical barrier for the application of CO_(2)enhanced coalbed methane recovery(CO_(2)-ECBM).Commonly,the intermittent CO_(2)injection,N2 displacing CO_(2)and pre-fracturing are the potential CO_(2)enhanced injectivity methods for coal reservoirs,but their mechanism and effectiveness remain to be clarified.This paper thus conducted small-scale experiments to simulate the working process of these engineering measures by an independently developed experimental device.Results show that the CO_(2)injectivity of coal is remarkably improved by the intermittent injection mode since the CO_(2)injection time is increased by folds and the loss of reservoir pressure can be complemented in time.The N_(2)displacing CO_(2)method promotes the desorption of CO_(2)and reduces the swelling strain,with the result that the permeability of coal is improved by 74.82%and 64.95%compared with the methods of the primary subcritical CO_(2)(Sub CO_(2))and supercritical CO_(2)(Sc CO_(2))injection.However,the permeability reduces again with the secondary CO_(2)injection.The permeability of the coal sample after pre-fracturing is averagely improved by 1-2 orders of magnitude,the irreversible permeability loss rate,average stress sensitivity coefficient and the permeability loss rate due to adsorption are averagely reduced by 95.885%,61.538%and 96.297%,respectively.This indicates that the permeability of coal after pre-fracturing is no longer sensitive to both the effective stress and Sc CO_(2)adsorption,the injectivity is thus improved and stable.The CO_(2)enhanced injectivity effects of the intermittent CO_(2)injection,the N_(2)displacing CO_(2)and the pre-fracturing are various,which thus can be selected individually or jointly to improve the CO_(2)injectivity according to the reservoir physical properties and geological conditions.This research deepens the understanding of the functional mechanism of CO_(2)enhanced injectivity methods and provides some guidance for their selection and application in engineering practices.
基金supported by the CNPC Scientific Research and Technology Development Project“Integration and industrialization of Improved Waterflooding Development Technologies for Thin Carbonate Reservoirs in Ahdab and Oman Block 5”(NO.2023ZZ19-08)for which we express our sincere gratitude-。
文摘Well injectivity decline during waterflooding is primarily attributed to retention of injected particles within pores,subsequently blocking flow channels in near-wellbore regions.Developing a predictive model to describe this problem holds significant value as it can inform the development of strategies aimed at preventing or mitigating such damage.Previous research has typically assumed a linear suspension flow or a constant filtration coefficient,which does not represent the near-wellbore suspension flow very well.In this paper,an analytical model for the radial suspension transport in porous media is derived based on the Langmuirian blocking filtration mechanism.Considering the dimensionless distance from the wellbore as a small parameter,we attain the analytical solution through an asymptotic expansion.To provide a basis for comparison,we also obtain numerical solutions using Shampine's code,which is based on the explicit central finite difference method.Comparison of the analytical and numerical solutions shows that their difference errors remain below 5%under waterflooding conditions.Based on the analytical solution for retained particle concentration,expressions for injection pressure,damage factor and damaged zone radius are also derived and are also expressed explicitly.In the end,we discuss two practical applications of our model:evaluation of existing acidizing jobs and designing new acidizing jobs,based on real field data from Tarim Basin,western China.The results indicate our model is practical in field operations.
文摘We consider an associated Riemannian metric induced by a rigging defined on a neighborhood of the null hypersurface in a Lorentzian manifold,and we connect this null geometry with the associated Riemannian geometry.Using a rigging defined on some open set containing the lightlike hypersurface,we introduce a global geometric invariant Rad^(ζ)(M)related to injectivity radius to a closed complete noncompact null hypersurface in a Lorentzian manifold.Using some comparison theorems from non-degenerated geometry,we give the relationship between geometry and topology of a closed complete noncompact null hypersurface with associated Riemannian metric and the asymptotic properties of injectivity radiuses at infinity.
基金Supported by National Natural Science Foundation of China (10001017)Scientific Research Foundation for Returned Overseas Chi
文摘For a commtative ring R and an injective cogenerator E in the category of R-modules, we characterize QF rings, IF rings and semihereditary rings by using the properties of the dual modules with respect to E.
基金the Natural Science Foundation of Education Department of Sichuan Province.and the Youth Science Foundation of Sichuan Province
文摘A right R-module E over a ring R is said to be maximally injective in case for any maximal right ideal m of R, every R-homomorphism f ： m → E can be extended to an R-homomorphism f^1 ： R → E. In this paper, we first construct an example to show that maximal injectivity is a proper generalization of injectivity. Then we prove that any right R-module over a left perfect ring R is maximally injective if and only if it is injective. We also give a partial affirmative answer to Faith＇s conjecture by further investigating the property of maximally injective rings. Finally, we get an approximation to Faith＇s conjecture, which asserts that every injective right R-module over any left perfect right self-injective ring R is the injective hull of a projective submodule.
文摘Regarding the enormous demands of numerous industries to fossil fuels,it is essential to select the proper enhanced oil recovery approaches for vertical and horizontal wells to supply the demands with the optimum expenditure.Water and gas injectivity as the secondary enhanced oil recovery techniques would be preferentially considered regarding their low costs of performances rather than chemical recovery and thermal techniques.Injected gas tends to push oil through pores or cracks in the matrix block and lead them to the production well.Therefore,injection of gas may significantly increase the recovery factor in these reservoirs.In this research,different injection scenarios in a fractured carbonate reservoir in the west of Iran are being simulated by the PVT modules of Eclipse software.The purpose of this research is to analyze the possibility of gradually increasing the extent of recovery by injecting carbon dioxide,methane,and water,and different injectivity patterns are considered in this research.The selection of injectivity patterns is severely based on the highest recycling rate of gas injection on different injection scenarios,and the injectivity scenarios were being compared with the natural depletion scenario.Consequently,Co2 injection(about 60%)had the highest oil recovery factor and CH4 and TB(about 54%and 53%)injectivity scenarios had the second and third highest rate of the oil recovery factor.
基金The authors would like to acknowledge“Curtin University Sarawak Malaysia”for funding this research through the Curtin Sarawak Research Institute(CSRI)Flagship scheme under the grant number CSRI 6015.We would like to thank Senergy Limited for the license of Interactive Petrophysics tool.
文摘Depleted gas reservoirs are used for a large-scale carbon dioxide(CO_(2))storage and reduction of the greenhouse gas released into the atmosphere.To identify a suitable depleted reservoir,it is essential to do a preliminary and comprehensive assessment of key storage factors such as storage capacity,injectivity,trapping mechanisms,and containment.However,there are a limited number of studies providing a preliminary assessment of CO_(2) injectivity potential in depleted gas reservoirs prior to a CO_(2) storage operation.The aim of this study is to provide a preliminary assessment of a gas field located in Malaysia for its storage potential based on subsurface characterization prior to injection.Evaluation of the reservoir interval based on the facies,cores,and wireline log data of a well located in the field indicated that the pore type and fabrics analysis is very beneficial to identify suitable locations for a successful storage practice.Although the results obtained are promising,it is recommended to combine this preliminary assessment with the fluid-mineral interactions analysis before making any judgment about reliability of storage sites.
文摘With its growth in spacecraft control applications,the microcontroller(MCU)becomes increasingly sensitive to radiation and the risks of system failure.In a radiation environment,the MCU is vulnerable to impacts from high-energy particles,which can lead to single-event effect(SEE)that disrupt normal system operations.The pipeline of MCU,being the core structure of the system,is particularly susceptible to single-event upset(SEU)and potentially causes execution failures.However,existing radiation-hardening techniques offer limited effectiveness for pipelines.To enhance SEU resistance,this study focused on a 32-bit MCU core with eight pipeline stages,proposing a pipeline hardening approach that utilizes lockstep technology to improve fault tolerance.Signals from two processors were compared including register write data,register contents and pre-fetched instructions.Any discrepancies triggered error flags to indicate faults.When an error flag was raised,recovery was initiated through an interrupt.The interrupt handler then retrieved state information from the advanced peripheral bus(APB)slave module to restore the CPU's operational state and resume execution.By combining hardware-based state preservation with software-driven error recovery,the proposed solution demonstrated significant improvements in fault tolerance rates and performance compared to traditional checkpoint-based techniques.After completing the pipeline hardening design,a fault injection platform was utilized in this paper to simulate real-world error conditions on internal processor modules.The platform was developed based on the circuit's register-transfer-level(RTL)design and statistical results.The fault injection platform was performed by automatically finding all registers within the target design.The register values were forced to upset at the tens of nanoseconds scale in the RTL description of the circuit's design.After running the circuit's functional simulation,the statistics of the faults in registers were displayed on the platform,which evaluated the influence of SEU.The vulnerability of SEU in the circuit could be observed from the results of the soft error statistics.The post-hardening soft error rates were then measured and compared to pre-hardening data,providing a quantitative evaluation of the improvements.Using this method,the soft error rates of the modules in the MCU core such as PFU,DPU,and Cache AXIM are 40.07%,26.36%,and 27.29%respectively before hardening.The soft error rates of modules mentioned above are reduced to 0%,0.69%,and 1.11%after hardening.The hardened and non-hardened designs of the entire core were implemented in FPGA.The total resource utilization of the triple mode redundancy(TMR)is 111984,as indicated by the number of look-up tables(LUTs)and registers consumed in the FPGA.The total resource utilization of this work is 78034,and the ratio of resource utilization between this work and TMR is approximately 69.68%.The error recovery time for the hardened MCU processor was analyzed using the completion cycles of a bubble sort algorithm as a benchmark.In this paper,the average recovery cycle using the software checkpoint roll-back method is 36479.06,and the average recovery cycle using this work is 26922.5.The ratio of recovery cycles between this work and checkpoint roll-back is about 73.8%.Assessments through random fault injection and FPGA implementation indicate that this approach effectively reduces processor faults caused by soft errors while optimizing resource utilization and efficiency over triplemodular redundancy.
文摘We use analytic methods in this paper to prove some new Enoki type injeetivity theorems on compact complex manifolds which generalize more or less the original Enoki injectivity theorem.
文摘We study the injectivity radius bound for 3-d Ricci flow with bounded curvature. As applications, we show the long time existence of the Ricci flow with positive Ricci curvature and with curvature decay condition at infinity. We partially settle a question of Chow-Lu-Ni [Hamilton＇s Ricci Flow, p. 302].
基金Supported by the Special Funds of Jiangsu Provincial Key Research and Development Projects,No.BE2019612Scientific Research Project Cooperated by Lanzhou Biotechnology Development Co.,Ltd.+3 种基金the Key R&D Program of Jiangsu Science and Technology Project,No.BE2022049 and No.BE2022049-1National Natural Science Foundation of China,No.82171249Nanjing Rehabilitation Medicine Center ProjectJiangsu Provincial Health Commission Special Fund for Aging and Health.
文摘BACKGROUND The previous studies have primarily focused on the influence of botulinum toxin A(BoNT-A)injection on emotions during the period of peak motor symptom improvement in blepharospasm patients,based on facial feedback hypothesis.AIM To evaluate the sustained anxiolytic and antidepressant effects of BoNT-A in blepharospasm patients beyond motor symptom control.METHODS We recruited benign essential blepharospasm patients with BoNT-A treatment and collected their data to compare scale scores of Jankovic Rating Scale,Blepharospasm Disability Index,Self-rating Anxiety Scale(SAS),Self-rating Depression Scale(SDS),Hamilton Anxiety Scale and Hamilton Depression Scale between pretreatment(baseline)and pre-reinjection(treatment),to further assess the effects of repeated treatments with BoNT by using sub-group analyses in the certain special states.RESULTS A total of 21 eligible blepharospasm patients were with the mean age of 58.4 years and a male-to-female ratio of 1:6.Significantly decreases in the subscale scores of SDS and SAS,including SDS well-being index,decreased capacity and hard to decide,SAS inability to sit still and headache were showed at post-a single BoNT-A injection when scale scores of Jankovic Rating Scale and Blepharospasm Disability Index were matched between baseline and posttreatment.With each additional BoNT-A injection,the odds ratio of patients with the moderate depressive symptoms decreased by 92.6%.Moreover,BoNT treatment remained a decrease in the subscale scores of SDS and SAS in patients with repeated injections.CONCLUSION This study is to demonstrate that repeated BoNT-A injection have a long-lasting relief for anxiety and depressive symptoms in blepharospasm even after its motor symptom-modulating effects have diminished.
基金financially supported by the National Natural Science Foundation of China(Nos.82272472 and 52373146)。
文摘Early knee osteoarthritis(KOA)is characterized by progressive degeneration of the articular cartilage,synovial inflammation,and excessive accumulation of reactive oxygen species(ROS).At present,intra-articular injection of hyaluronic acid(HA)is widely used to alleviate symptoms;however,its lubrication persistence,antioxidant,and anti-inflammatory abilities are limited,and it is difficult to effectively delay the early process of cartilage degeneration.Based on this,hyaluronic acid-g-lipoic acid(HA-LA)was synthesized by esterification reaction,and HA-LA microspheres were prepared by a reversed-phase emulsion method,which was combined with a macromolecular HA-LA solution to form injectable hydrogels.The objective of this study was to evaluate the efficacy of an injectable hydrogel based on hyaluronic acid-g-lipoic acid microspheres(HA-LA MS)for the treatment of KOA and to verify its injectability,lubricity,reactive oxygen species(ROS)scavenging ability,and anti-inflammatory effects.The results show that the HA-LA MS hydrogel has excellent shear thinning characteristics and continuous injectability,and its microsphere structure significantly reduces the interfacial friction coefficient through the rolling effect.In vitro experiments have shown that the hydrogel can efficiently scavenge ROS,reduce the expression of inflammatory factors,and is non-cytotoxic.The HA-LA MS injectable hydrogel has excellent lubricity,ROS scavenging ability,and anti-inflammatory effects in vivo,which can effectively delay the degeneration of early KOA cartilage,and its efficacy is significantly better than that of traditional hyaluronic acid,making it a promising intra-articular injection preparation.
文摘Objective:To compare the clinical efficacy and safety of intravitreal injection of faricimab and conbercept in the treatment of diabetic macular edema(DME).Methods:A total of 50 patients diagnosed with DME in our hospital from January 2023 to May 2025 were selected and randomly divided into an observation group and a control group,with 25 cases in each group,using a random number table method.The observation group received intravitreal injection of faricimab,while the control group received intravitreal injection of conbercept.Both groups adopted a loading phase plus maintenance phase treatment regimen.The best-corrected visual acuity(BCVA,expressed in logMAR)and central subfield thickness(CST)of the two groups were compared before treatment and at 1,3,and 6 months after treatment,and the incidence of adverse events during treatment was recorded.Results:The logMAR BCVA in the observation group was lower than that in the control group at 3 and 6 months after treatment(both p<0.05).The CST in the observation group was smaller than that in the control group at 1,3,and 6 months after treatment(all p<0.05).There was no statistically significant difference in the overall incidence of adverse events between the two groups(χ^(2)=0.189,p=0.663).Conclusion:Both intravitreal injections of faricimab and conbercept are effective in improving visual acuity and reducing macular edema in patients with DME,with good safety profiles.However,faricimab demonstrates superior efficacy in the medium to long term(3 and 6 months)compared to conbercept,making it more suitable for long-term treatment of patients with DME.
基金Supported by the National Natural Science Foundation of China(Grant No.12061061)the Young Talents Team Project of Gansu Province(Grant No.2025QNTD49)+1 种基金Lanshan Talent Project of Northwest Minzu University(Grant No.Xbmulsrc202412)Longyuan Young Talents of Gansu Province.
文摘In this paper,we study two types of the Ding injective dimensions of complexes.First,we provide some equivalent characterizations of the dimension related to the special Ding injec-tive preenvelopes.Furthermore,we consider the relationship between the dimensions Dipd(Y)and Did(Y)of the complex Y,where Dipd(Y)denotes the dimension associated with special Ding injective preenvelopes,and Did(Y)denotes the dimension associated with DG-injective resolutions.It is demonstrated that Dipd(Y)=Did(Y)for any bounded complex Y.
基金the National Natural Science Foundation of China(No.52374347)Yulin Science and Technology Program Project(No.2024-SF-227)Key Research and Development Program of Shaanxi(No.2021GY-128).
文摘To address the kinetic constraints inherent in the catalytic combustion of pulverized coal injection under low heating-rate conditions within conventional air atmospheres,a drop tube furnace was utilized to simulate the catalytic combustion of pulverized coal(PC).The effects of gas composition,oxygen concentration,the type,and the content of catalysts on the combustion reactivity were systematically analyzed.Furthermore,the structural changes of unburned pulverized coal were also examined.Experimental results indicate that as the oxygen concentration increased from 21%to 79%,compared with the O_(2)/N_(2)condition,the increment in the burnout rate of PC under the O_(2)/CO_(2)condition increased from 3%to 23%.After the addition of catalysts,including hematite,metallurgical oil sludge,and light-burnt dolomite(LBD),under the condition of 21%oxygen concentration,the effects of the three catalysts under the O_(2)/CO_(2)condition were superior to those under the O_(2)/N_(2)condition.This trend was reversed under the conditions of 38%and 79%oxygen concentrations.In all atmospheres,the three catalysts can enhance the burnout rate of PC.Among them,LBD exhibits the most favorable effect,and there exists an optimal dosage.Mechanistic analysis through scanning electron microscopy,X-ray diffraction,and N_(2)adsorption-desorption reveals that under 21%O_(2)/79%CO_(2)conditions,high-concentration CO_(2)leads to the formation of pores,and additives accelerate the oxidation of C and the gasification of CO_(2)through oxygen transfer,thereby enhancing the burnout rate of PC.
