As the penetration rate of distributed energy increases,the transient power angle stability problem of the virtual synchronous generator(VSG)has gradually become prominent.In view of the situation that the grid impeda...As the penetration rate of distributed energy increases,the transient power angle stability problem of the virtual synchronous generator(VSG)has gradually become prominent.In view of the situation that the grid impedance ratio(R/X)is high and affects the transient power angle stability of VSG,this paper proposes a VSG transient power angle stability control strategy based on the combination of frequency difference feedback and virtual impedance.To improve the transient power angle stability of the VSG,a virtual impedance is adopted in the voltage loop to adjust the impedance ratio R/X;and the PI control feedback of the VSG frequency difference is introduced in the reactive powervoltage link of theVSGto enhance the damping effect.Thesecond-orderVSGdynamic nonlinearmodel considering the reactive power-voltage loop is established and the influence of different proportional integral(PI)control parameters on the system balance stability is analyzed.Moreover,the impact of the impedance ratio R/X on the transient power angle stability is presented using the equal area criterion.In the simulations,during the voltage dips with the reduction of R/X from 1.6 to 0.8,Δδ_(1)is reduced from 0.194 rad to 0.072 rad,Δf_(1)is reduced from 0.170 to 0.093 Hz,which shows better transient power angle stability.Simulation results verify that compared with traditional VSG,the proposedmethod can effectively improve the transient power angle stability of the system.展开更多
This study examines the influence of magnetic field and temperature on the transient voltage of a polycrystalline silicon radial junction solar cell in a dynamic regime under multispectral illumination. Radial junctio...This study examines the influence of magnetic field and temperature on the transient voltage of a polycrystalline silicon radial junction solar cell in a dynamic regime under multispectral illumination. Radial junction solar cells represent a major advancement in photovoltaic technologies, as they optimize light absorption and charge collection efficiency. The focus is on the impact of the magnetic field and temperature on the decay of transient voltage, which provides crucial information on recombination processes and the lifetime of minority carriers. The results reveal that the magnetic field tends to increase the transient voltage by directly affecting the transient electron density. Indeed, for B > 7 × 10−5 T, the magnetic field prolongs the relaxation time by increasing the transient voltage amplitude. Additionally, rising temperatures accelerate (ranging from 290 K to 450 K) recombination processes, thereby reducing the transient voltage, although this effect is moderated by the presence of a magnetic field. The study highlights the complex interaction between magnetic field and temperature, with significant impacts on the transient behaviour.展开更多
Background Cotton is an important crop providing the most natural fibers all over the world. The cotton genomics community has utilized whole genome sequencing data to construct an elite gene pool in which functional ...Background Cotton is an important crop providing the most natural fibers all over the world. The cotton genomics community has utilized whole genome sequencing data to construct an elite gene pool in which functional genes are related to agronomic traits. However, the functional validation of these genes is hindered by time-consuming and inefficient genetic transformation methods. Thus, establishing a transient transformation system of high efficiency is necessary for cotton genomics.Results To improve the efficiency of transient transformation, we used the protoplasts isolated from the etiolated cotyledon as recipient. The enzymatic digestion buffer comprised 1.5%(w/v) cellulase, 0.75%(w/v) macerozyme, and 1% hemicellulase, osmotically buffered with 0.4 mol·L^(-1) mannitol. After 5 h of dark incubation at 25℃, uniform cotton protoplasts were successfully isolated with a yield of 4.6 × 10^(6) protoplasts per gram(fresh weight) and 95% viability. We incubated 100 μL protoplasts(2.5 × 10^(5)·m L^(-1)) with 15 μg plasmid in the solution of 0.4 mol·L^(-1) mannitol and 40% PEG 4000 for 15 min, ultimately achieving an optimal transient transfection efficiency of 71.47%.Conclusions This transient system demonstrated effective utility in cellular biology research through successful applications in subcellular localization analyses, bimolecular fluorescence complementation(Bi FC) verification, and prime editing vector validation. Through systematic optimization, we established an efficient and expedited protoplast-based transient transformation system and successfully applied this platform to cotton functional genomics studies.展开更多
Panax Ginseng(2n=48)represents a quintessential resource in traditional Chinese medicine,renowned for its outstanding medicinal and economic benefits(Choi,2008).But the late start in analyzing the ginseng genome and t...Panax Ginseng(2n=48)represents a quintessential resource in traditional Chinese medicine,renowned for its outstanding medicinal and economic benefits(Choi,2008).But the late start in analyzing the ginseng genome and the poorly developed genetic transformation system still impede the study of ginseng gene function and the application of molecular breeding.Transient transformation has the advantages of high efficiency,low cost,and short cycle while laying the foundation for stable genetic transformation(Chen et al.,2021).In the plant transformation process,the cell wall prevents exogenous DNA or protein entry,significantly reducing the efficiency of the transformation.Protoplasts,as exposed cells wrapped by the plasma membrane,are more likely to absorb exogenous DNA,RNA,and protein.Transgenic systems of protoplasts have been established in several species and applied in many fields,such as gene function research(Gou et al.,2020),gene editing(Yang et al.,2023),and physiological or molecular mechanism research(Aoyagi,2011).For instance,Oryza sativa protoplasts were employed to screen genes involved in rice defense signaling pathways through fluorescent reporter systems,with BiFC employed to verified inter-protein interactions(He et al.,2016).A study transformed Cannabis sativa L.protoplasts with the plasmids carrying GFP and RFP genes,evaluated the efficiency under different transformation conditions by flow cytometry,and verified the induction of synthetic DR5 promoter by IAA based on the constructed system(Beard et al.,2021).展开更多
Transient electronics is a versatile tool that finds applications in various fields,including medical biology,environmental protection,and data information security.In the context of data protection,the traditional pa...Transient electronics is a versatile tool that finds applications in various fields,including medical biology,environmental protection,and data information security.In the context of data protection,the traditional passive degradation transient mode is being replaced by the active destruction mode,which features a short self-destruction time and provides greater resistance to recovery.This article presents an overview of recent progress in transient electronics,assessing the benefits and suitability of varying transient mechanisms.The article also analyses the influence of transient electronics on military security while emphasizing the advantages of implementing energetic materials.Besides,the article introduces energetic transient devices and evaluates their ability to support the autonomous operation of transient electronic devices.展开更多
A nickel-catalyzed C(sp^(2))–H alkynylation of unprotected α-substituted benzylamines is achieved by utilizing a transient directing group. The combination of a TDG with a nickel catalyst significantly improves the ...A nickel-catalyzed C(sp^(2))–H alkynylation of unprotected α-substituted benzylamines is achieved by utilizing a transient directing group. The combination of a TDG with a nickel catalyst significantly improves the reaction step and atom economy. It has been investigated that the 2,4,6-trimethylpyridine ligand was critical to achieve the optimized reactivity. This protocol provides a straightforward route for synthesizing the alkynylated free benzylamines, featuring good substrate compatibility and monoselectivity.展开更多
Transient negative capacitance(NC),as an available dynamic charge effect achieved in resistor-ferroelectric capacitor(R-FEC)circuits,has triggered a series of theoretical and experimental works focusing on its physica...Transient negative capacitance(NC),as an available dynamic charge effect achieved in resistor-ferroelectric capacitor(R-FEC)circuits,has triggered a series of theoretical and experimental works focusing on its physical mechanism and device application.Here,we analytically derived the effects of different mechanical conditions on the transient NC behaviors in the R-FEC circuit based on the phenomenological model.It shows that the ferroelectric capacitor can exhibit either NC(i.e.,“single NC”and“double NC”)or positive capacitance,depending on the mechanical condition and temperature.Further numerical calculations show that the voltage drop caused by NC can be effectively controlled by temperature,applied stress,or strain.The relationship between NC voltage drop and system configurations including external resistance,dynamical coefficient of polarization,and input voltage are presented,showing diverse strategies to manipulate the NC effect.These results provide theoretical guidelines for rational design and efficient control of NC-related electronic devices.展开更多
A pre-swirl system with a multi-chamber structure is crucial to the secondary air system of an aero engine.The airflow within the pre-swirl system(characterized by high-speed rotation and compressible flow)is complica...A pre-swirl system with a multi-chamber structure is crucial to the secondary air system of an aero engine.The airflow within the pre-swirl system(characterized by high-speed rotation and compressible flow)is complicated.During transient processes in aero engine operation,the pre-swirl system is subjected to upstream fluctuations,which is a less studied aspect.This paper delves into the unsteady flow characteristics within the pre-swirl system.We investigate the influence of different pressure-fluctuation boundary conditions,corresponding to step function,ramp function,and sine function,on the transient response characteristics of the pre-swirl system.The results indicate that the response characteristics are strongly affected by the upstream boundary conditions.An obvious overshoot phenomenon is observed in the actual temperature drop under the step and ramp function conditions.The peak time of the step function is 75%shorter compared to the ramp function.Furthermore,the flow parameters exhibit nonlinear growth during the transient process,emphasizing the need for consideration in future quasi-steady simulations.For the sine function condition,the pressure-fluctuation frequency minimally affects stable values of mass flow rate and actual temperature drop but exerts a substantial influence on the maximum deviation of actual temperature drop of the system.As the frequency increases from 100 Hz to 200 Hz,the maximum deviations for actual temperature drop change from around±13 K to±10 K.展开更多
In this study,the wave motion in elastodynamics for unbounded media is modeled using an unsplit-field perfectly matched layer(PML)formulation that is solved by employing an isogeometric analysis(IGA).In the adopted co...In this study,the wave motion in elastodynamics for unbounded media is modeled using an unsplit-field perfectly matched layer(PML)formulation that is solved by employing an isogeometric analysis(IGA).In the adopted combination,the non-uniform rational B-spline(NURBS)functions are employed as basis functions.Moreover,the unbounded and artificial domains,defined in the PML method,are contained in a single patch domain.Based on the proposed scheme,the approximation of the geometry problem is set in a new scheme in which the PML’s absorbing and attenuation properties and the description of traveling waves can be represented.This includes a higher continuity and smoother approximation of the computed domain.As high-order NURBS basis functions are non-interpolatory,a penalty method is present to apply a time-dependent displacement load.The performance of the NURBS-based PML is analyzed through numerical examples for 1D and 2D domains,considering homogeneous and heterogeneous media.Further,we verify the long-time numerical stability of the present method.The developed method can be used to simulate hypothetical stratified domains commonly encountered in soil-structure interaction analyses.展开更多
Small modular reactors have received widespread attention owing to their inherent safety,low investment,and flexibility.Small pressurized water reactors(SPWRs)have become important candidates for SMRs owing to their h...Small modular reactors have received widespread attention owing to their inherent safety,low investment,and flexibility.Small pressurized water reactors(SPWRs)have become important candidates for SMRs owing to their high technological maturity.Since the Fukushima accident,research on accident-tolerant fuels(ATFs),which are more resistant to serious accidents than conventional fuels,has gradually increased.This study analyzes the neutronics and thermal hydraulics of an SPWR(ACPR50S)for different ATFs,BeO+UO_(2)−SiC,BeO+UO_(2)−FeCrAl,U_(3)Si_(2)−SiC,and U_(3)Si_(2)−FeCrAl,based on a PWR fuel management code,the Bamboo-C deterministic code.In the steady state,the burnup calculations,reactivity coefficients,power and temperature distributions,and control rod reactivity worth were studied.The transients of the control rod ejection accident for the two control rods with the maximum and minimum reactivity worth were analyzed.The results showed that 5%B-10 enrichment in the wet annular burnable absorbers assembly can effectively reduce the initial reactivity and end-of-life reactivity penalty.The BeO+UO2−SiC core exhibited superior neutronic characteristics in terms of burnup and negative temperature reactivity compared with the other three cases owing to the strong moderation ability of BeO+UO_(2)and low neutron absorption of SiC.However,the U_(3)Si_(2)core had a marginally better power-flattening effect than BeO+UO_(2),and the differential worth of each control rod group was similar between different ATFs.During the transient of a control rod ejection,the changes in the fuel temperature,coolant temperature,and coolant density were similar.The maximum difference was less than 10℃ for the fuel temperature and 2℃ for the coolant temperature.展开更多
The traditional transient stability assessment(TSA)model for power systems has three disadvantages:capturing critical information during faults is difficult,aperiodic and oscillatory unstable conditions are not distin...The traditional transient stability assessment(TSA)model for power systems has three disadvantages:capturing critical information during faults is difficult,aperiodic and oscillatory unstable conditions are not distinguished,and poor generalizability is exhibited by systems with high renewable energy penetration.To address these issues,a novel ResGRU architecture for TSA is proposed in this study.First,a residual neural network(ResNet)is used for deep feature extraction of transient information.Second,a bidirectional gated recurrent unit combined with a multi-attention mechanism(BiGRU-Attention)is used to establish temporal feature dependencies.Their combination constitutes a TSA framework based on the ResGRU architecture.This method predicts three transient conditions:oscillatory instability,aperiodic instability,and stability.The model was trained offline using stochastic gradient descent with a thermal restart(SGDR)optimization algorithm in the offline training phase.This significantly improves the generalizability of the model.Finally,simulation tests on IEEE 145-bus and 39-bus systems confirmed that the proposed method has higher adaptability,accuracy,scalability,and rapidity than the conventional TSA approach.The proposed model also has superior robustness for PMU incomplete configurations,PMU noisy data,and packet loss.展开更多
This review comprehensively explores the theory and applications of attosecond transient absorption spectroscopy(ATAS)in studying ultrafast electronic dynamics across various systems,from atoms to solids.Driven by sig...This review comprehensively explores the theory and applications of attosecond transient absorption spectroscopy(ATAS)in studying ultrafast electronic dynamics across various systems,from atoms to solids.Driven by significant advancements in ultrafast laser technology,such as generating isolated attosecond pulses,ATAS enables detailed investigations of ultrafast electronic processes with unprecedented time resolution.The article introduces the fundamental principles and historical development of ATAS.Applications of ATAS are discussed in three main domains:in atoms,where it has been used to study build-up dynamics of Autler–Townes splitting,Fano resonance,light-induced states,etc.;in molecules,where it has revealed coherent molecular wavepacket dynamics and non-adiabatic dynamics near conical intersections;and in solids,where it has been extended to investigate ultrafast charge carrier dynamics in metals,semiconductors,and insulators.The review highlights the potential of ATAS in developing ultrafast optical switches and petahertz electronics.The ability of ATAS to probe and manipulate electronic dynamics at the attosecond timescale provides a powerful tool for exploring the fundamental limits of electronic and optical processes in materials.展开更多
In this study,the potential application of shaped charge jets as transient antennas for electromagnetic signal transmission was explored and an electromagnetic pulse radiation system with a shaped charge jet as a tran...In this study,the potential application of shaped charge jets as transient antennas for electromagnetic signal transmission was explored and an electromagnetic pulse radiation system with a shaped charge jet as a transient antenna was proposed.During the research,crucial characteristics of the transient antenna formed by a shaped charge with a 30 mm diameter,such as resonant frequency,radiation pattern,and radiation efficiency,were evaluated.The typical shaped charge jet morphology was obtained based on the simulations,in which it could insight the dynamic behavior of the shaped charge jet selected.An equivalent model experiment was employed to test the radiation efficiency,and it showed that a shorting pin loading method could increase the relative bandwidth of the jet antenna to 32.8%,and the experimental results correlate with the theoretical predictions for half-wave dipole antennas reasonably well.Additionally,variations in the diameter of the shaped charge jet were found to affect the input impedance and impedance bandwidth,while the length of the jet influenced the resonant frequency of the antenna.This suggests that altering these parameters can achieve reconfigurability of the jet antenna.展开更多
The traditional detailed model of the dual active bridge(DAB)power electronic transformer is characterized by the high dimensionality of its nodal admittance matrix and the need for a small simulation step size,which ...The traditional detailed model of the dual active bridge(DAB)power electronic transformer is characterized by the high dimensionality of its nodal admittance matrix and the need for a small simulation step size,which limits the speed of electromagnetic transient(EMT)simulations.To overcome these limitations,a novel EMT equivalent model based on a generalized branch-cutting method is proposed to improve the simulation efficiency of the DAB model.The DAB topology is first decomposed into two subnetworks through branch-cutting and node-tearing methods without the introduction of a one-time-step delay.Sub-sequently,the internal nodes of each sub-network are eliminated through network simplification,and the equivalent circuit for the port cascade module is derived.The model is then validated through simulations across various operating conditions.The results demonstrate that the model avoids the loss of accuracy associated with one-time-step delay,the relative error across different conditions remains below 1%,and the simulation acceleration ratios improve as the number of modules increases.展开更多
The attosecond extreme ultraviolet(XUV) pulse pump and femtosecond infrared(IR) pulse probe scheme is commonly used to study the dynamics and attosecond transient absorption(ATA) spectra of microscopic systems. In a r...The attosecond extreme ultraviolet(XUV) pulse pump and femtosecond infrared(IR) pulse probe scheme is commonly used to study the dynamics and attosecond transient absorption(ATA) spectra of microscopic systems. In a recent report [Proc. Natl. Acad. Sci. USA 121 e2307836121(2024)], we showed that shaped XUV pulses with spectral minima can significantly alter the absorption line shape of helium's 2s2p doubly excited state within a few tens of attoseconds.However, it remains unclear if similar effects could be observed in a singly excited state. In this study, we use shaped XUV pulses to excite helium's 2p singly excited state and couple the 2p and 3d states with a delayed IR pulse. Comparing these results with those from Gaussian XUV pulses, we find that the ATA spectra for the shaped XUV pulses exhibit more pronounced changes with delay, while the changes for the Gaussian pulses are gradual. We also explain these differences through population changes and analytical models. Our findings show that shaped XUV pulses can regulate the dynamics and absorption spectra of a singly excited state.展开更多
Insight into exciton dynamics of two-dimensional(2D)transition metal dichalcogenides(TMDs)is critical for the optimization of their performance in photonic and optoelectronic devices.Although current researches have p...Insight into exciton dynamics of two-dimensional(2D)transition metal dichalcogenides(TMDs)is critical for the optimization of their performance in photonic and optoelectronic devices.Although current researches have primarily concentrated on the near-resonant excitation scenario in 2D TMDs,the case of excitation energies resonating with highenergy excitons or higher energies has yet to be fully elucidated.Here,a comparative analysis is conducted between highenergy excitation(360 nm)and near-resonant excitation(515 nm)utilizing transient absorption spectroscopy to achieve a comprehensive understanding of the exciton dynamics within monolayer WS_(2).It is observed that the high-energy C-exciton can be generated via an up-conversion process under 515 nm excitation,even the energy of which is less than that of the C-exciton.Furthermore,the capacity to efficiently occupy band-edge A-exciton states leads to longer lifetimes for both the C-excitons and the A-excitons under conditions of near-resonant excitation,accompanied by an augmented rate of radiative recombination.This study provides a paradigm for optimizing the performance of 2D TMDs-based devices by offering valuable insights into their exciton dynamics.展开更多
BACKGROUND Noninvasive tests are crucial for the management and follow-up of patients with autoimmune hepatitis,but their validation is limited because of insufficient data.AIM To investigate the diagnostic performanc...BACKGROUND Noninvasive tests are crucial for the management and follow-up of patients with autoimmune hepatitis,but their validation is limited because of insufficient data.AIM To investigate the diagnostic performance of three fibrosis noninvasive tests[FibroTest,vibration-controlled transient elastography(VCTE),and the fibrosis-4 index(FIB-4)and two activity biomarkers(alanine aminotransferase(ALT)and ActiTest].METHODS This study enrolled 103 patients for whom liver biopsy,hepatic elastography results,and laboratory markers were available.Diagnostic performance was assessed with receiver operating characteristic(ROC)curves,the Obuchowski measure(OM),and the Bayesian latent class model.RESULTS FibroTest and VCTE outperformed FIB-4 in cases of significant fibrosis(≥F2),with areas under the ROC curve of 0.83[95%confidence interval(CI):0.73-0.90],0.86(95%CI:0.77-0.92),and 0.71(95%CI:0.60-0.80),respectively.The mean(standard error)OM values were 0.92(0.01),0.93(0.01),and 0.88(0.02)for FibroTest,VCTE,and FIB-4,respectively;FibroTest and VCTE performed comparably,and both were superior to FIB-4(P=0.03 and P=0.005).The areas under the ROC curve values for activity biomarkers were 0.86(95%CI:0.76-0.92)for ActiTest and 0.84(95%CI:0.73-0.90)for ALT(P=0.06).The OM values for ActiTest and ALT were 0.92(0.02)and 0.90(0.02),respectively(P=0.005).CONCLUSION FibroTest and VCTE outperformed FIB-4 according to the OM.FibroTest-ActiTest facilitated the evaluation of both fibrosis and activity.展开更多
With the continuous expansion and increasing complexity of power system scales,the binary classifica-tion for transient stability assessment in power systems can no longer meet the safety requirements of power system ...With the continuous expansion and increasing complexity of power system scales,the binary classifica-tion for transient stability assessment in power systems can no longer meet the safety requirements of power system control and regulation.Therefore,this paper proposes a multi-class transient stability assessment model based on an improved Transformer.The model is designed with a dual-tower encoder structure:one encoder focuses on the time dependency of data,while the other focuses on the dynamic correlations between variables.Feature extraction is conducted from both time and variable perspectives to ensure the completeness of the feature extraction process,thereby enhancing the accuracy of multi-class evaluation in power systems.Additionally,this paper introduces a hybrid sampling strategy based on sample boundaries,which addresses the issue of sample imbalance by increasing the number of boundary samples in the minority class and reducing the number of non-boundary samples in the majority class.Considering the frequent changes in power grid topology or operation modes,this paper proposes a two-stage updating scheme based on self-supervised learning:In the first stage,self-supervised learning is employed to mine the structural information from unlabeled data in the target domain,enhancing the model’s generalization capability in new scenarios.In the second stage,a sample screening mechanism is used to select key samples,which are labeled through long-term simulation techniques for fine-tuning the model parameters.This allows for rapid model updates without relying on many labeled samples.This paper’s proposed model and update scheme have been simulated and verified on two node systems,the IEEE New England 10-machine 39-bus system and the IEEE 47-machine 140-bus system,demonstrating their effectiveness and reliability.展开更多
It is generally believed that cuttings have a significant impact on the forces of tubular string in extended-reach drilling.However,there are few studies attempted to investigate and quantify it.In this paper,a three-...It is generally believed that cuttings have a significant impact on the forces of tubular string in extended-reach drilling.However,there are few studies attempted to investigate and quantify it.In this paper,a three-layer transient model for cuttings transport is established to simulate the characteristics of dynamic cuttings transport over time under various conditions.The simulation results indicate that the change in drilling parameters like ROP(rate of penetration)and flow rate of drilling fluid will lead to the non-uniform distribution of cuttings bed.And the alternation of drilling and circulation will lead to a clear wavy distribution of cuttings bed in the wellbore.Then,the effect of cuttings on tubular string is obtained through a large number of numerical simulations and the nonlinear regression method,and this influence is introduced into the conventional stiff rod model of tubular string.Finally,the transient model for cuttings transport is coupled with the modified tubular mechanic model and applies to a case study of extended-reach drilling.The results show that there is a delay effect for the effect of the changes in drilling parameters on the ground torques because the changes in drilling parameters occur instantaneously,while the changes in cuttings bed distribution are slow due to its low transport velocity.Based on the coupling analysis of transient cuttings transport and tubular mechanical behaviors,the drilling parameters are optimized,including the recommended adjustment period and adjustment range for the ROP,the proper drilling time for the increased flow rate.Furthermore,the circulation and back reaming are optimized.For circulation,the keys are choosing appropriate time interval between the two adjacent circulations and the time for each circulation.To avoid pipe stuck,at least 20 min of circulation is required to remove the cuttings bed near the large-sized BHA((Bottom Hole Assembly))before back reaming,and the maximum back reaming velocity should be smaller than the minimum transport velocity of the uniform bed.展开更多
Hydraulic fracturing and commingle production of multiple layers are extensively adopted in unconventional tight gas reservoirs.Accurate determination of parameters of individual layers in multilayered tight gas reser...Hydraulic fracturing and commingle production of multiple layers are extensively adopted in unconventional tight gas reservoirs.Accurate determination of parameters of individual layers in multilayered tight gas reservoirs is essential for well performance evaluation and development strategy optimization.However,most analytical models for fractured vertical wells in stratified gas reservoirs focus on fully penetrated hydraulic fractures,neglecting the influence of partial penetration of hydraulic fractures.This paper presents a semi-analytical model to investigate the transient pressure behavior of vertically fractured wells in dual porosity multi-layered tight gas reservoirs.The partial penetration of hydraulic fracture,the vertical heterogeneities of layer properties,the differences between hydraulic fracture lengths in each layer and the stress sensitivity are all incorporated in the proposed model.The point-source solution,Laplace transformation,Fourier transformation,Pedrosa's transformation,perturbation technique,and the superposition principle are applied to obtain the analytical solution of transient pressure responses.The proposed model is validated against a commercial software,and the transient pressure behavior of vertically fractured wells in multi-layered tight gas reservoirs are analyzed.Based on the characteristics of the type curves,seven flow regimes can be identified,including wellbore storage,transitional flow period,reservoir linear flow period,vertical pseudo-radial flow in fracture system,inter-porosity flow period,late-time pseudo-radial flow period,and the boundary-dominated flow period.Sensitivity analyses reveal that the penetration ratio of hydraulic fracture has primary influence on early-time transient pressure behavior and production contribution,while the stress sensitivity mainly affects the late-time transient pressure behavior.Gas production at the initial stage is mainly contributed by the high-pressure/high-permeability layer,and gas backflow will occur during initial production stage for obviously unequal initial formation pressures.Finally,two field cases are conducted to illustrate the applicability of the proposed model.The model and corresponding conclusions can provide technical support for performance analysis of tight gas reservoirs.展开更多
基金supported by theMajor Science and Technology Projects of China Southern Power Grid(Grant number CGYKJXM20210328).
文摘As the penetration rate of distributed energy increases,the transient power angle stability problem of the virtual synchronous generator(VSG)has gradually become prominent.In view of the situation that the grid impedance ratio(R/X)is high and affects the transient power angle stability of VSG,this paper proposes a VSG transient power angle stability control strategy based on the combination of frequency difference feedback and virtual impedance.To improve the transient power angle stability of the VSG,a virtual impedance is adopted in the voltage loop to adjust the impedance ratio R/X;and the PI control feedback of the VSG frequency difference is introduced in the reactive powervoltage link of theVSGto enhance the damping effect.Thesecond-orderVSGdynamic nonlinearmodel considering the reactive power-voltage loop is established and the influence of different proportional integral(PI)control parameters on the system balance stability is analyzed.Moreover,the impact of the impedance ratio R/X on the transient power angle stability is presented using the equal area criterion.In the simulations,during the voltage dips with the reduction of R/X from 1.6 to 0.8,Δδ_(1)is reduced from 0.194 rad to 0.072 rad,Δf_(1)is reduced from 0.170 to 0.093 Hz,which shows better transient power angle stability.Simulation results verify that compared with traditional VSG,the proposedmethod can effectively improve the transient power angle stability of the system.
文摘This study examines the influence of magnetic field and temperature on the transient voltage of a polycrystalline silicon radial junction solar cell in a dynamic regime under multispectral illumination. Radial junction solar cells represent a major advancement in photovoltaic technologies, as they optimize light absorption and charge collection efficiency. The focus is on the impact of the magnetic field and temperature on the decay of transient voltage, which provides crucial information on recombination processes and the lifetime of minority carriers. The results reveal that the magnetic field tends to increase the transient voltage by directly affecting the transient electron density. Indeed, for B > 7 × 10−5 T, the magnetic field prolongs the relaxation time by increasing the transient voltage amplitude. Additionally, rising temperatures accelerate (ranging from 290 K to 450 K) recombination processes, thereby reducing the transient voltage, although this effect is moderated by the presence of a magnetic field. The study highlights the complex interaction between magnetic field and temperature, with significant impacts on the transient behaviour.
基金supported by Biological Breeding of Early Maturing and Disease Resistant Cotton Varieties (NO.2023ZD04041)the Project of China Agriculture Research System (Grant No. CARS-15-06)+2 种基金Natural Science Foundation of Henan Province (Grant No. 232300421041 and 222300420382)National Natural Science Foundation of China (Grant No. U21 A20213)the Central Public-interest Scientific Institution Basal Research Fund (Grant No. 1610162023017 and 1610162023028)。
文摘Background Cotton is an important crop providing the most natural fibers all over the world. The cotton genomics community has utilized whole genome sequencing data to construct an elite gene pool in which functional genes are related to agronomic traits. However, the functional validation of these genes is hindered by time-consuming and inefficient genetic transformation methods. Thus, establishing a transient transformation system of high efficiency is necessary for cotton genomics.Results To improve the efficiency of transient transformation, we used the protoplasts isolated from the etiolated cotyledon as recipient. The enzymatic digestion buffer comprised 1.5%(w/v) cellulase, 0.75%(w/v) macerozyme, and 1% hemicellulase, osmotically buffered with 0.4 mol·L^(-1) mannitol. After 5 h of dark incubation at 25℃, uniform cotton protoplasts were successfully isolated with a yield of 4.6 × 10^(6) protoplasts per gram(fresh weight) and 95% viability. We incubated 100 μL protoplasts(2.5 × 10^(5)·m L^(-1)) with 15 μg plasmid in the solution of 0.4 mol·L^(-1) mannitol and 40% PEG 4000 for 15 min, ultimately achieving an optimal transient transfection efficiency of 71.47%.Conclusions This transient system demonstrated effective utility in cellular biology research through successful applications in subcellular localization analyses, bimolecular fluorescence complementation(Bi FC) verification, and prime editing vector validation. Through systematic optimization, we established an efficient and expedited protoplast-based transient transformation system and successfully applied this platform to cotton functional genomics studies.
基金supported by the Genetic analysis of important quality and traits of ginseng and basic research on molecular design breeding(Grant No.U21A20405)。
文摘Panax Ginseng(2n=48)represents a quintessential resource in traditional Chinese medicine,renowned for its outstanding medicinal and economic benefits(Choi,2008).But the late start in analyzing the ginseng genome and the poorly developed genetic transformation system still impede the study of ginseng gene function and the application of molecular breeding.Transient transformation has the advantages of high efficiency,low cost,and short cycle while laying the foundation for stable genetic transformation(Chen et al.,2021).In the plant transformation process,the cell wall prevents exogenous DNA or protein entry,significantly reducing the efficiency of the transformation.Protoplasts,as exposed cells wrapped by the plasma membrane,are more likely to absorb exogenous DNA,RNA,and protein.Transgenic systems of protoplasts have been established in several species and applied in many fields,such as gene function research(Gou et al.,2020),gene editing(Yang et al.,2023),and physiological or molecular mechanism research(Aoyagi,2011).For instance,Oryza sativa protoplasts were employed to screen genes involved in rice defense signaling pathways through fluorescent reporter systems,with BiFC employed to verified inter-protein interactions(He et al.,2016).A study transformed Cannabis sativa L.protoplasts with the plasmids carrying GFP and RFP genes,evaluated the efficiency under different transformation conditions by flow cytometry,and verified the induction of synthetic DR5 promoter by IAA based on the constructed system(Beard et al.,2021).
基金supported by the National Natural Science Foun-dation of China(Grant No.52206165)Key R&D Projects in Sichuan Province(Grant No.2022YFG0219)。
文摘Transient electronics is a versatile tool that finds applications in various fields,including medical biology,environmental protection,and data information security.In the context of data protection,the traditional passive degradation transient mode is being replaced by the active destruction mode,which features a short self-destruction time and provides greater resistance to recovery.This article presents an overview of recent progress in transient electronics,assessing the benefits and suitability of varying transient mechanisms.The article also analyses the influence of transient electronics on military security while emphasizing the advantages of implementing energetic materials.Besides,the article introduces energetic transient devices and evaluates their ability to support the autonomous operation of transient electronic devices.
基金supported financially by the Excellent Going Abroad Expert's Training Program in Hebei Province (No. 201940)the Hebei Natural Science Foundation of China (No. H2020208030)the S & T Program of Hebei (No. 22567607H) for financial support。
文摘A nickel-catalyzed C(sp^(2))–H alkynylation of unprotected α-substituted benzylamines is achieved by utilizing a transient directing group. The combination of a TDG with a nickel catalyst significantly improves the reaction step and atom economy. It has been investigated that the 2,4,6-trimethylpyridine ligand was critical to achieve the optimized reactivity. This protocol provides a straightforward route for synthesizing the alkynylated free benzylamines, featuring good substrate compatibility and monoselectivity.
基金This work was supported by the National Natural Science Foundation of China(Grants Nos.12222214,12132020,12002400,and 12172386)by Guangdong Provincial Key Laboratory of Magnetoelectric Physics and Devices(Grant No.2022B1212010008)+1 种基金by the National Natural Science Foundation of Guangdong Province(Grant No.2021B1515020021)by the Shenzhen Science and Techonlogy Program(Grant Nos.202206193000001 and 20220818181805001).
文摘Transient negative capacitance(NC),as an available dynamic charge effect achieved in resistor-ferroelectric capacitor(R-FEC)circuits,has triggered a series of theoretical and experimental works focusing on its physical mechanism and device application.Here,we analytically derived the effects of different mechanical conditions on the transient NC behaviors in the R-FEC circuit based on the phenomenological model.It shows that the ferroelectric capacitor can exhibit either NC(i.e.,“single NC”and“double NC”)or positive capacitance,depending on the mechanical condition and temperature.Further numerical calculations show that the voltage drop caused by NC can be effectively controlled by temperature,applied stress,or strain.The relationship between NC voltage drop and system configurations including external resistance,dynamical coefficient of polarization,and input voltage are presented,showing diverse strategies to manipulate the NC effect.These results provide theoretical guidelines for rational design and efficient control of NC-related electronic devices.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDC0160000)the National Natural Science Foundation of China(No.52122603)+4 种基金the Excellence Research Group Program(No.52488101)the Shandong Provincial Natural Science Foundation of China(No.ZR2024JQ011)the Project of National Key Laboratory of Science and Technology on Advanced Light-duty Gas-turbine(No.2023-JJ-Y04)the National Science and Technology Major Project of China(No.J2019-III-0003-0046)the Taishan Scholars Program of China.
文摘A pre-swirl system with a multi-chamber structure is crucial to the secondary air system of an aero engine.The airflow within the pre-swirl system(characterized by high-speed rotation and compressible flow)is complicated.During transient processes in aero engine operation,the pre-swirl system is subjected to upstream fluctuations,which is a less studied aspect.This paper delves into the unsteady flow characteristics within the pre-swirl system.We investigate the influence of different pressure-fluctuation boundary conditions,corresponding to step function,ramp function,and sine function,on the transient response characteristics of the pre-swirl system.The results indicate that the response characteristics are strongly affected by the upstream boundary conditions.An obvious overshoot phenomenon is observed in the actual temperature drop under the step and ramp function conditions.The peak time of the step function is 75%shorter compared to the ramp function.Furthermore,the flow parameters exhibit nonlinear growth during the transient process,emphasizing the need for consideration in future quasi-steady simulations.For the sine function condition,the pressure-fluctuation frequency minimally affects stable values of mass flow rate and actual temperature drop but exerts a substantial influence on the maximum deviation of actual temperature drop of the system.As the frequency increases from 100 Hz to 200 Hz,the maximum deviations for actual temperature drop change from around±13 K to±10 K.
文摘In this study,the wave motion in elastodynamics for unbounded media is modeled using an unsplit-field perfectly matched layer(PML)formulation that is solved by employing an isogeometric analysis(IGA).In the adopted combination,the non-uniform rational B-spline(NURBS)functions are employed as basis functions.Moreover,the unbounded and artificial domains,defined in the PML method,are contained in a single patch domain.Based on the proposed scheme,the approximation of the geometry problem is set in a new scheme in which the PML’s absorbing and attenuation properties and the description of traveling waves can be represented.This includes a higher continuity and smoother approximation of the computed domain.As high-order NURBS basis functions are non-interpolatory,a penalty method is present to apply a time-dependent displacement load.The performance of the NURBS-based PML is analyzed through numerical examples for 1D and 2D domains,considering homogeneous and heterogeneous media.Further,we verify the long-time numerical stability of the present method.The developed method can be used to simulate hypothetical stratified domains commonly encountered in soil-structure interaction analyses.
基金supported by the National Natural Science Foundation of China (No. 12205150)Natural Science Foundation of Jiangsu Province (No. BK20210304)+1 种基金China Postdoctoral Science Foundation (Nos. 2020M681594 and 2019TQ0148)Jiangsu Province Postdoctoral Science Foundation (Nos. 2020Z231)
文摘Small modular reactors have received widespread attention owing to their inherent safety,low investment,and flexibility.Small pressurized water reactors(SPWRs)have become important candidates for SMRs owing to their high technological maturity.Since the Fukushima accident,research on accident-tolerant fuels(ATFs),which are more resistant to serious accidents than conventional fuels,has gradually increased.This study analyzes the neutronics and thermal hydraulics of an SPWR(ACPR50S)for different ATFs,BeO+UO_(2)−SiC,BeO+UO_(2)−FeCrAl,U_(3)Si_(2)−SiC,and U_(3)Si_(2)−FeCrAl,based on a PWR fuel management code,the Bamboo-C deterministic code.In the steady state,the burnup calculations,reactivity coefficients,power and temperature distributions,and control rod reactivity worth were studied.The transients of the control rod ejection accident for the two control rods with the maximum and minimum reactivity worth were analyzed.The results showed that 5%B-10 enrichment in the wet annular burnable absorbers assembly can effectively reduce the initial reactivity and end-of-life reactivity penalty.The BeO+UO2−SiC core exhibited superior neutronic characteristics in terms of burnup and negative temperature reactivity compared with the other three cases owing to the strong moderation ability of BeO+UO_(2)and low neutron absorption of SiC.However,the U_(3)Si_(2)core had a marginally better power-flattening effect than BeO+UO_(2),and the differential worth of each control rod group was similar between different ATFs.During the transient of a control rod ejection,the changes in the fuel temperature,coolant temperature,and coolant density were similar.The maximum difference was less than 10℃ for the fuel temperature and 2℃ for the coolant temperature.
基金financially supported by State Key Laboratory of HVDC No.SKLHVDC-2023-KF-03.
文摘The traditional transient stability assessment(TSA)model for power systems has three disadvantages:capturing critical information during faults is difficult,aperiodic and oscillatory unstable conditions are not distinguished,and poor generalizability is exhibited by systems with high renewable energy penetration.To address these issues,a novel ResGRU architecture for TSA is proposed in this study.First,a residual neural network(ResNet)is used for deep feature extraction of transient information.Second,a bidirectional gated recurrent unit combined with a multi-attention mechanism(BiGRU-Attention)is used to establish temporal feature dependencies.Their combination constitutes a TSA framework based on the ResGRU architecture.This method predicts three transient conditions:oscillatory instability,aperiodic instability,and stability.The model was trained offline using stochastic gradient descent with a thermal restart(SGDR)optimization algorithm in the offline training phase.This significantly improves the generalizability of the model.Finally,simulation tests on IEEE 145-bus and 39-bus systems confirmed that the proposed method has higher adaptability,accuracy,scalability,and rapidity than the conventional TSA approach.The proposed model also has superior robustness for PMU incomplete configurations,PMU noisy data,and packet loss.
基金Project supported by the National Natural Science Foundation of China(Grant No.12174034)。
文摘This review comprehensively explores the theory and applications of attosecond transient absorption spectroscopy(ATAS)in studying ultrafast electronic dynamics across various systems,from atoms to solids.Driven by significant advancements in ultrafast laser technology,such as generating isolated attosecond pulses,ATAS enables detailed investigations of ultrafast electronic processes with unprecedented time resolution.The article introduces the fundamental principles and historical development of ATAS.Applications of ATAS are discussed in three main domains:in atoms,where it has been used to study build-up dynamics of Autler–Townes splitting,Fano resonance,light-induced states,etc.;in molecules,where it has revealed coherent molecular wavepacket dynamics and non-adiabatic dynamics near conical intersections;and in solids,where it has been extended to investigate ultrafast charge carrier dynamics in metals,semiconductors,and insulators.The review highlights the potential of ATAS in developing ultrafast optical switches and petahertz electronics.The ability of ATAS to probe and manipulate electronic dynamics at the attosecond timescale provides a powerful tool for exploring the fundamental limits of electronic and optical processes in materials.
基金supported by the"Fundamental Research Funds for the Central Universities"(Grant No.30924010801).
文摘In this study,the potential application of shaped charge jets as transient antennas for electromagnetic signal transmission was explored and an electromagnetic pulse radiation system with a shaped charge jet as a transient antenna was proposed.During the research,crucial characteristics of the transient antenna formed by a shaped charge with a 30 mm diameter,such as resonant frequency,radiation pattern,and radiation efficiency,were evaluated.The typical shaped charge jet morphology was obtained based on the simulations,in which it could insight the dynamic behavior of the shaped charge jet selected.An equivalent model experiment was employed to test the radiation efficiency,and it showed that a shorting pin loading method could increase the relative bandwidth of the jet antenna to 32.8%,and the experimental results correlate with the theoretical predictions for half-wave dipole antennas reasonably well.Additionally,variations in the diameter of the shaped charge jet were found to affect the input impedance and impedance bandwidth,while the length of the jet influenced the resonant frequency of the antenna.This suggests that altering these parameters can achieve reconfigurability of the jet antenna.
基金The Technology Project of State Grid Corporation of China Headquarters(No.5400-202318547A-3-2-ZN).
文摘The traditional detailed model of the dual active bridge(DAB)power electronic transformer is characterized by the high dimensionality of its nodal admittance matrix and the need for a small simulation step size,which limits the speed of electromagnetic transient(EMT)simulations.To overcome these limitations,a novel EMT equivalent model based on a generalized branch-cutting method is proposed to improve the simulation efficiency of the DAB model.The DAB topology is first decomposed into two subnetworks through branch-cutting and node-tearing methods without the introduction of a one-time-step delay.Sub-sequently,the internal nodes of each sub-network are eliminated through network simplification,and the equivalent circuit for the port cascade module is derived.The model is then validated through simulations across various operating conditions.The results demonstrate that the model avoids the loss of accuracy associated with one-time-step delay,the relative error across different conditions remains below 1%,and the simulation acceleration ratios improve as the number of modules increases.
基金Project supported by the National Natural Science Foundation of China (Grant No. 12274230)the Funding of Nanjing University of Science and Technology (Grant No. TSXK2022D005)。
文摘The attosecond extreme ultraviolet(XUV) pulse pump and femtosecond infrared(IR) pulse probe scheme is commonly used to study the dynamics and attosecond transient absorption(ATA) spectra of microscopic systems. In a recent report [Proc. Natl. Acad. Sci. USA 121 e2307836121(2024)], we showed that shaped XUV pulses with spectral minima can significantly alter the absorption line shape of helium's 2s2p doubly excited state within a few tens of attoseconds.However, it remains unclear if similar effects could be observed in a singly excited state. In this study, we use shaped XUV pulses to excite helium's 2p singly excited state and couple the 2p and 3d states with a delayed IR pulse. Comparing these results with those from Gaussian XUV pulses, we find that the ATA spectra for the shaped XUV pulses exhibit more pronounced changes with delay, while the changes for the Gaussian pulses are gradual. We also explain these differences through population changes and analytical models. Our findings show that shaped XUV pulses can regulate the dynamics and absorption spectra of a singly excited state.
基金supported by the National Natural Science Foundation of China(Grant Nos.12474421 and 12104066)the Fund from Education Department of Jilin Province(Grant Nos.JJKH20250473KJ and JJKH20241413KJ)the Fund from Department of Science and Technology of Jilin Province(Grant No.YDZJ202101ZYTS041)。
文摘Insight into exciton dynamics of two-dimensional(2D)transition metal dichalcogenides(TMDs)is critical for the optimization of their performance in photonic and optoelectronic devices.Although current researches have primarily concentrated on the near-resonant excitation scenario in 2D TMDs,the case of excitation energies resonating with highenergy excitons or higher energies has yet to be fully elucidated.Here,a comparative analysis is conducted between highenergy excitation(360 nm)and near-resonant excitation(515 nm)utilizing transient absorption spectroscopy to achieve a comprehensive understanding of the exciton dynamics within monolayer WS_(2).It is observed that the high-energy C-exciton can be generated via an up-conversion process under 515 nm excitation,even the energy of which is less than that of the C-exciton.Furthermore,the capacity to efficiently occupy band-edge A-exciton states leads to longer lifetimes for both the C-excitons and the A-excitons under conditions of near-resonant excitation,accompanied by an augmented rate of radiative recombination.This study provides a paradigm for optimizing the performance of 2D TMDs-based devices by offering valuable insights into their exciton dynamics.
文摘BACKGROUND Noninvasive tests are crucial for the management and follow-up of patients with autoimmune hepatitis,but their validation is limited because of insufficient data.AIM To investigate the diagnostic performance of three fibrosis noninvasive tests[FibroTest,vibration-controlled transient elastography(VCTE),and the fibrosis-4 index(FIB-4)and two activity biomarkers(alanine aminotransferase(ALT)and ActiTest].METHODS This study enrolled 103 patients for whom liver biopsy,hepatic elastography results,and laboratory markers were available.Diagnostic performance was assessed with receiver operating characteristic(ROC)curves,the Obuchowski measure(OM),and the Bayesian latent class model.RESULTS FibroTest and VCTE outperformed FIB-4 in cases of significant fibrosis(≥F2),with areas under the ROC curve of 0.83[95%confidence interval(CI):0.73-0.90],0.86(95%CI:0.77-0.92),and 0.71(95%CI:0.60-0.80),respectively.The mean(standard error)OM values were 0.92(0.01),0.93(0.01),and 0.88(0.02)for FibroTest,VCTE,and FIB-4,respectively;FibroTest and VCTE performed comparably,and both were superior to FIB-4(P=0.03 and P=0.005).The areas under the ROC curve values for activity biomarkers were 0.86(95%CI:0.76-0.92)for ActiTest and 0.84(95%CI:0.73-0.90)for ALT(P=0.06).The OM values for ActiTest and ALT were 0.92(0.02)and 0.90(0.02),respectively(P=0.005).CONCLUSION FibroTest and VCTE outperformed FIB-4 according to the OM.FibroTest-ActiTest facilitated the evaluation of both fibrosis and activity.
基金the National Natural Science Foundation of China(5227-7084).
文摘With the continuous expansion and increasing complexity of power system scales,the binary classifica-tion for transient stability assessment in power systems can no longer meet the safety requirements of power system control and regulation.Therefore,this paper proposes a multi-class transient stability assessment model based on an improved Transformer.The model is designed with a dual-tower encoder structure:one encoder focuses on the time dependency of data,while the other focuses on the dynamic correlations between variables.Feature extraction is conducted from both time and variable perspectives to ensure the completeness of the feature extraction process,thereby enhancing the accuracy of multi-class evaluation in power systems.Additionally,this paper introduces a hybrid sampling strategy based on sample boundaries,which addresses the issue of sample imbalance by increasing the number of boundary samples in the minority class and reducing the number of non-boundary samples in the majority class.Considering the frequent changes in power grid topology or operation modes,this paper proposes a two-stage updating scheme based on self-supervised learning:In the first stage,self-supervised learning is employed to mine the structural information from unlabeled data in the target domain,enhancing the model’s generalization capability in new scenarios.In the second stage,a sample screening mechanism is used to select key samples,which are labeled through long-term simulation techniques for fine-tuning the model parameters.This allows for rapid model updates without relying on many labeled samples.This paper’s proposed model and update scheme have been simulated and verified on two node systems,the IEEE New England 10-machine 39-bus system and the IEEE 47-machine 140-bus system,demonstrating their effectiveness and reliability.
基金support from the Natural Science Foundation of China(Grant Nos.52222401,52234002,52394255)National Key Research and Development Program of China(Grant No.2023YFC2810901)Science Foundation of China University of Petroleum,Beijing(Grant No.ZXZX20230083).
文摘It is generally believed that cuttings have a significant impact on the forces of tubular string in extended-reach drilling.However,there are few studies attempted to investigate and quantify it.In this paper,a three-layer transient model for cuttings transport is established to simulate the characteristics of dynamic cuttings transport over time under various conditions.The simulation results indicate that the change in drilling parameters like ROP(rate of penetration)and flow rate of drilling fluid will lead to the non-uniform distribution of cuttings bed.And the alternation of drilling and circulation will lead to a clear wavy distribution of cuttings bed in the wellbore.Then,the effect of cuttings on tubular string is obtained through a large number of numerical simulations and the nonlinear regression method,and this influence is introduced into the conventional stiff rod model of tubular string.Finally,the transient model for cuttings transport is coupled with the modified tubular mechanic model and applies to a case study of extended-reach drilling.The results show that there is a delay effect for the effect of the changes in drilling parameters on the ground torques because the changes in drilling parameters occur instantaneously,while the changes in cuttings bed distribution are slow due to its low transport velocity.Based on the coupling analysis of transient cuttings transport and tubular mechanical behaviors,the drilling parameters are optimized,including the recommended adjustment period and adjustment range for the ROP,the proper drilling time for the increased flow rate.Furthermore,the circulation and back reaming are optimized.For circulation,the keys are choosing appropriate time interval between the two adjacent circulations and the time for each circulation.To avoid pipe stuck,at least 20 min of circulation is required to remove the cuttings bed near the large-sized BHA((Bottom Hole Assembly))before back reaming,and the maximum back reaming velocity should be smaller than the minimum transport velocity of the uniform bed.
基金supported by the National Natural Science Foundation of China(Grant Nos.52174036,52234003)the Sichuan Province Science and Technology Program(Grant No.2024NSFSC0199)the Joint Fund for Innovation and Development of Chongqing Natural Science Foundation(Grant No.2023NSCQ-LZX0184).
文摘Hydraulic fracturing and commingle production of multiple layers are extensively adopted in unconventional tight gas reservoirs.Accurate determination of parameters of individual layers in multilayered tight gas reservoirs is essential for well performance evaluation and development strategy optimization.However,most analytical models for fractured vertical wells in stratified gas reservoirs focus on fully penetrated hydraulic fractures,neglecting the influence of partial penetration of hydraulic fractures.This paper presents a semi-analytical model to investigate the transient pressure behavior of vertically fractured wells in dual porosity multi-layered tight gas reservoirs.The partial penetration of hydraulic fracture,the vertical heterogeneities of layer properties,the differences between hydraulic fracture lengths in each layer and the stress sensitivity are all incorporated in the proposed model.The point-source solution,Laplace transformation,Fourier transformation,Pedrosa's transformation,perturbation technique,and the superposition principle are applied to obtain the analytical solution of transient pressure responses.The proposed model is validated against a commercial software,and the transient pressure behavior of vertically fractured wells in multi-layered tight gas reservoirs are analyzed.Based on the characteristics of the type curves,seven flow regimes can be identified,including wellbore storage,transitional flow period,reservoir linear flow period,vertical pseudo-radial flow in fracture system,inter-porosity flow period,late-time pseudo-radial flow period,and the boundary-dominated flow period.Sensitivity analyses reveal that the penetration ratio of hydraulic fracture has primary influence on early-time transient pressure behavior and production contribution,while the stress sensitivity mainly affects the late-time transient pressure behavior.Gas production at the initial stage is mainly contributed by the high-pressure/high-permeability layer,and gas backflow will occur during initial production stage for obviously unequal initial formation pressures.Finally,two field cases are conducted to illustrate the applicability of the proposed model.The model and corresponding conclusions can provide technical support for performance analysis of tight gas reservoirs.
