The coupled formation of wax crystals and hydrates is a critical issue for the safety of deep-sea oil and gas exploration and subsea transport pipeline flow.Therefore,this paper conducts an experimental study on the c...The coupled formation of wax crystals and hydrates is a critical issue for the safety of deep-sea oil and gas exploration and subsea transport pipeline flow.Therefore,this paper conducts an experimental study on the characteristics of methane hydrate formation in a water-in-oil(W/O)system with different wax crystal contents and explores the influence of different initial experimental pressures on the induction period and maximum rate of hydrate formation.The wavelet function was introduced to process the reaction rate and calculate the maximum speed of hydrate formation.Notably,the higher the pressure,the smaller the maximum rate of hydrate formation.We observed that wax crystal precipitation increases the viscosity of the emulsion,which limits the diffusion of gas in the liquid phase during hydrate nucleation and thus delays the hydrate nucleation.The methane gas precipitation also affects the remaining fraction’s wax content and therefore affects the wax precipitation.Secondary hydrate formation was observed several times during the experiment,increasing the risk of pipeline blockage.Overall,this work provides insights into the effect of wax crystal precipitation on hydrate behaviour that could facilitate flow assurance applications in subsea multiphase pipelines and inform the safe transportation of oil and gas pipelines.展开更多
In this article,we investigate a fractional-order singular Leslie-Gower prey-predator bioeconomic model,which describes the interaction bet ween populations of prey and predator,and takes into account the economic int...In this article,we investigate a fractional-order singular Leslie-Gower prey-predator bioeconomic model,which describes the interaction bet ween populations of prey and predator,and takes into account the economic interest.We firstly obtain the solvability condition and the st ability of the model sys tem,and discuss the singularity induced bifurcation phenomenon.Next,we introduce a st ate feedback controller to elimina te the singularity induced bifurcation phenomenon,and discuss the optimal control problems.Finally,numerical solutions and their simulations are considered in order to illustrate the theoretical results and reveal the more complex dynamical behavior.展开更多
The ongoing outbreak of Severe Acute Respiratory Syndrome Coronavirus 2(SARS-CoV-2)pandemic has posed significant challenges in early viral diagnosis.Hence,it is urgently desirable to develop a rapid,inexpensive,and s...The ongoing outbreak of Severe Acute Respiratory Syndrome Coronavirus 2(SARS-CoV-2)pandemic has posed significant challenges in early viral diagnosis.Hence,it is urgently desirable to develop a rapid,inexpensive,and sensitive method to aid point-of-care SARS-CoV-2 detection.In this work,we report a highly sequence-specific biosensor based on nanocomposites with aggregationinduced emission luminogens(AIEgen)-labeled oligonucleotide probes on graphene oxide nanosheets(AIEgen@GO)for one step-detection of SARS-CoV-2-specific nucleic acid sequences(Orf1ab or N genes).A dual“turn-on”mechanism based on AIEgen@GO was established for viral nucleic acids detection.Here,the first-stage fluorescence recovery was due to dissociation of the AIEgen from GO surface in the presence of target viral nucleic acid,and the second-stage enhancement of AIEbased fluorescent signal was due to the formation of a nucleic acid duplex to restrict the intramolecular rotation of the AIEgen.Furthermore,the feasibility of our platform for diagnostic application was demonstrated by detecting SARS-CoV-2 virus plasmids containing both Orf1ab and N genes with rapid detection around 1 h and good sensitivity at pM level without amplification.Our platform shows great promise in assisting the initial rapid detection of the SARS-CoV-2 nucleic acid sequence before utilizing quantitative reverse transcription-polymerase chain reaction for second confirmation.展开更多
基金supported by National Natural Science Foundation of China(Major Program No.U19B200052)Science and Technology Innovation Seedling Project of Sichuan Province,China(No.2021079)+2 种基金NationalNatural Science Foundation Young Scientists Fund of China(No.51904259)School-Level Key Program of Chengdu Technological University,China(Nos.2021ZR0062022ZR019).
文摘The coupled formation of wax crystals and hydrates is a critical issue for the safety of deep-sea oil and gas exploration and subsea transport pipeline flow.Therefore,this paper conducts an experimental study on the characteristics of methane hydrate formation in a water-in-oil(W/O)system with different wax crystal contents and explores the influence of different initial experimental pressures on the induction period and maximum rate of hydrate formation.The wavelet function was introduced to process the reaction rate and calculate the maximum speed of hydrate formation.Notably,the higher the pressure,the smaller the maximum rate of hydrate formation.We observed that wax crystal precipitation increases the viscosity of the emulsion,which limits the diffusion of gas in the liquid phase during hydrate nucleation and thus delays the hydrate nucleation.The methane gas precipitation also affects the remaining fraction’s wax content and therefore affects the wax precipitation.Secondary hydrate formation was observed several times during the experiment,increasing the risk of pipeline blockage.Overall,this work provides insights into the effect of wax crystal precipitation on hydrate behaviour that could facilitate flow assurance applications in subsea multiphase pipelines and inform the safe transportation of oil and gas pipelines.
文摘In this article,we investigate a fractional-order singular Leslie-Gower prey-predator bioeconomic model,which describes the interaction bet ween populations of prey and predator,and takes into account the economic interest.We firstly obtain the solvability condition and the st ability of the model sys tem,and discuss the singularity induced bifurcation phenomenon.Next,we introduce a st ate feedback controller to elimina te the singularity induced bifurcation phenomenon,and discuss the optimal control problems.Finally,numerical solutions and their simulations are considered in order to illustrate the theoretical results and reveal the more complex dynamical behavior.
基金Shenzhen-Hong Kong-Macao Science and Technology Plan Project,Grant/Award Number:SGDX2020110309260000Research Grants Council(RGC)Collaborative Research Fund,Grant/Award Number:C5110-20GF+2 种基金Research Grants Council(RGC)General Research Fund,Grant/Award Numbers:PolyU 15214619,PolyU 15210818Hong Kong Polytechnic University Internal Fund,Grant/Award Numbers:1-ZE1E,1-ZVVQNational Natural Science Foundation of China,Grant/Award Number:31771077。
文摘The ongoing outbreak of Severe Acute Respiratory Syndrome Coronavirus 2(SARS-CoV-2)pandemic has posed significant challenges in early viral diagnosis.Hence,it is urgently desirable to develop a rapid,inexpensive,and sensitive method to aid point-of-care SARS-CoV-2 detection.In this work,we report a highly sequence-specific biosensor based on nanocomposites with aggregationinduced emission luminogens(AIEgen)-labeled oligonucleotide probes on graphene oxide nanosheets(AIEgen@GO)for one step-detection of SARS-CoV-2-specific nucleic acid sequences(Orf1ab or N genes).A dual“turn-on”mechanism based on AIEgen@GO was established for viral nucleic acids detection.Here,the first-stage fluorescence recovery was due to dissociation of the AIEgen from GO surface in the presence of target viral nucleic acid,and the second-stage enhancement of AIEbased fluorescent signal was due to the formation of a nucleic acid duplex to restrict the intramolecular rotation of the AIEgen.Furthermore,the feasibility of our platform for diagnostic application was demonstrated by detecting SARS-CoV-2 virus plasmids containing both Orf1ab and N genes with rapid detection around 1 h and good sensitivity at pM level without amplification.Our platform shows great promise in assisting the initial rapid detection of the SARS-CoV-2 nucleic acid sequence before utilizing quantitative reverse transcription-polymerase chain reaction for second confirmation.
