This study investigates the impact of pore network characteristics on fluid flow through complex and heterogeneous porous media,providing insights into the factors affecting fluid propagation in such systems.Specifica...This study investigates the impact of pore network characteristics on fluid flow through complex and heterogeneous porous media,providing insights into the factors affecting fluid propagation in such systems.Specifically,high-resolution or micro X-ray computed tomography(CT)imaging techniques were utilized to examine outcrop stromatolite samples of the Lagoa Salgada,considered flow analogous to the Brazilian Pre-salt carbonate reservoirs.The petrophysical results comprised two distinct stromatolite depositional facies,the columnar and the fine-grained facies.By generating pore network model(PNM),the study quantified the relationship between key features of the porous system,including pore and throat radius,throat length,coordination number,shape factor,and pore volume.The study found that the less dense pore network of the columnar sample is typically characterized by larger pores and wider and longer throats but with a weaker connection of throats to pores.Both facies exhibited less variability in the radius of the pores and throats in comparison to throat length.Additionally,a series of core flooding experiments coupled with medical CT scanning was designed and conducted in the plug samples to assess flow propagation and saturation fields.The study revealed that the heterogeneity and presence of disconnected or dead-end pores significantly impacted the flow patterns and saturation.Two-phase flow patterns and oil saturation distribution reveal a preferential and heterogeneous displacement that mainly swept displaced fluid in some regions of plugs and bypassed it in others.The relation between saturation profiles,porosity profiles,and the number of fluid flow patterns for the samples was evident.Only for the columnar plug sample was the enhancement in recovery factor after shifting to lower salinity water injection(SB)observed.展开更多
The generalized integral transform technique （GITT） is used to find a semianalytical numerical solution for dynamic response of an axially moving Timoshenko beam with clamped-clamped and simply-supported boundary co...The generalized integral transform technique （GITT） is used to find a semianalytical numerical solution for dynamic response of an axially moving Timoshenko beam with clamped-clamped and simply-supported boundary conditions, respectively. The implementation of GITT approach for analyzing the forced vibration equation eliminates the space variable and leads to systems of second-order ordinary differential equations （ODEs） in time. The MATHEMATICA built-in function, NDSolve, is used to numerically solve the resulting transformed ODE system. The good convergence behavior of the suggested eigenfunction expansions is demonstrated for calculating the transverse deflection and the angle of rotation of the beam cross-section. Moreover, parametric studies are performed to analyze the effects of the axially moving speed, the axial tension, and the amplitude of external distributed force on the vibration amplitude of axially moving Timoshenko beams.展开更多
This paper describes a three-dimensional(3D) numerical analysis of a test embankment on geotextileencased columns(GECs), in comparison with two-dimensional(2D) axisymmetric and plane strain analyses. The 3D numerical ...This paper describes a three-dimensional(3D) numerical analysis of a test embankment on geotextileencased columns(GECs), in comparison with two-dimensional(2D) axisymmetric and plane strain analyses. The 3D numerical analysis was performed considering a rectangular strip under the embankment centerline. The 2D analysis was also carried out using axisymmetric unit cell and plane strain approaches.Numerical results indicated that the adopted 3D strip model represented well the measured deformations and pore pressure evolution during embankment construction and post-contraction periods.Unlike the unit cell model, both plane strain and 3D analyses could properly determine the settlement profile along the embankment base as well as the profile of the horizontal soil deformation beneath the embankment toes. The plane strain analysis, however, was not able to compute the geotextile ring force which might be simply calculated using the axisymmetric unit cell approach. The paper also showed that, due to horizontal boundary fixities applied to the embankment borders, the unit cell model clearly underestimated the tension developed in the basal geogrid.展开更多
As there are no specific guidelines on design of subsea pipelines crossing active seismic faults, methods for land buried pipelines have been applied to. Taking the large seismic fault movement into account, this pape...As there are no specific guidelines on design of subsea pipelines crossing active seismic faults, methods for land buried pipelines have been applied to. Taking the large seismic fault movement into account, this paper proposes improved methods for seismic designs of subsea pipelines by comprehensively investigating the real constraining of soil on the pipelines, the interaction processes of soil with the pipeline, the plastic slippage of the soil, and the elastic-plastic properties of the pipeline materials. New formulas are given to calculate the length of transition section and its total elongation. These formulas are more reasonable in mechanism, and more practical for seismic design of subsea pipelines crossing active faults.展开更多
The methodology to obtain the non-linear roll damping from decay tests is very old. It has been proposed by Froude in the 19th century and used from then on. Behind it there is a quadratic model [θ｜θ｜] for the dam...The methodology to obtain the non-linear roll damping from decay tests is very old. It has been proposed by Froude in the 19th century and used from then on. Behind it there is a quadratic model [θ｜θ｜] for the damping and a subsequent equivalent linearization. Probably all model basin in the world follows this approach to assess the damping from a methods to get the P1-P2 coefficients. This is very applied to any kind of hull. However, it has become decay test. This is well documented and so is the general in the sense that in principle, it could be clear that for hull with a flat bottom such as a very large crude carrier （VLCC）, this approach may lead to confusing results such as negative P2. Faced with this, the work presents a completely new idea. Avoiding the polynomial approximation, the basic attitude is to devise two regions from the decaying test response. The first, called the large amplitude response region yields a larger damping, probably due to the large bilge keel vortices that are attracted to the hull flat bottom. The second is the small amplitude response region where the vortices are not attracted to the bottom but travels approximately 45° sidewise. These observations has led to a new approach called the bi-linear approach as discussed in the work after analyzing several （many） model test results. In fact, a new modified bi-linear approach is ultimately proposed after the understanding of a transition region instead of a transition angle.展开更多
Along with the consumption increase of the petroleum products, more countries have transferred their attentions to the offshore fields, especially the deepwater oil and gas reserves. For deepwater exploitation, the ri...Along with the consumption increase of the petroleum products, more countries have transferred their attentions to the offshore fields, especially the deepwater oil and gas reserves. For deepwater exploitation, the risers must be installed to act as the conduits connecting surface platforms to subsea facilities. In this paper, the typical risers sorted by different classes are introduced, and the correspondent installation methods are presented. By investigating the recent projects performed in the deepwater hot spots, and combining the challenges of HYSY20 l for riser installation, a lifting device developed for assisting riser installation is proposed and detailed to satisfy the installation of deepwater risers in the LW3-1 Gas Field of 1500 m in the South China Sea. Tests on both the functions and performances of such a new system exhibit the satisfaction of meeting all challenging requirements of HYSY201 for application to riser installation in waters up to a depth of 3000 m in the South China Sea.展开更多
Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3, Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300-900℃. The auto-th...Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3, Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300-900℃. The auto-thermal reforming occurs in two simultaneous stages, namely, total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O2 conversion of 100% starting from 450℃. For combination with CO2 reforming, the Pt/CeO2 catalyst showed the lowest initial activity at 800℃, and the highest stability over 40 h on-stream. This catalyst also presented the best performance for the reaction with steam at 800℃. The higher resistance to coke formation of the catalyst supported on ceria is due to the metal-support interactions and the higher mobility of oxygen in the oxide lattice.展开更多
The kinetics of the Fischer-Tropsch reaction over a Co/Nb2O5 catalyst in a fixed bed reactor was investigated experimentally. Experiments were carried out under isothermal and isobaric conditions （T=543 K, P=2.1 MPa...The kinetics of the Fischer-Tropsch reaction over a Co/Nb2O5 catalyst in a fixed bed reactor was investigated experimentally. Experiments were carried out under isothermal and isobaric conditions （T=543 K, P=2.1 MPa） and under different conditions of several H2/CO feed molar ratio （0.49-4.79）, space velocities （0.2-3.8 h^-1）, mass of catalyst （0.3-1.5 g）, and CO conversion （10%-29%）. Synthesis gas conversion was measured and data were reduced to estimate the kinetic parameters for different Langmuir-Hinshelwood rate expressions. Differential and integral reactor models were used for the nonlinear regression of kinetics parameters. One of the rate equations could well explain the data. The hydrocarbon product distributions that were experimentally determined exhibited an unusual behavior, and a possible explanation was discussed.展开更多
This paper presents a proposal for an experimental salt cavern in offshore ultra-deep water for CO2 abatement,including the instrumentation plan and well conceptual design evaluated for carbon capture and storage(CCS)...This paper presents a proposal for an experimental salt cavern in offshore ultra-deep water for CO2 abatement,including the instrumentation plan and well conceptual design evaluated for carbon capture and storage(CCS)application.These studies are based on applied computational mechanics associated with field experimentation that has contributed to the technical feasibility of the underground potash mine at the State of Sergipe in Brazil.This knowhow allowed the stability analysis of several salt caverns for brine production at the State of Alagoas in Brazil and to the drilling through stratified thick layers of salt of the pre-salt reservoirs in Santos Basin.Now,this knowledge has been applied in the design of onshore and offshore salt caverns opened by dissolution for storage of natural gas and CO2.The geomechanical study,through the application of computational mechanics,of offshore giant salt caverns of 450 m high by 150 m in diameter,shows that one cavern can store about 4 billion Sm3 or 7.2 million tons of CO2.Before the construction of the giant cavern,which will be the first gas storage offshore in the world,it has been decided to develop an experimental one,with smaller size,to obtained field parameters.The experimental cavern will allow the calibration of parameters to be used in the structural integrity analysis of the cavern and well for storage of natural gas which is rich in CO2 under high pressure.展开更多
The nonlinear dynamic behaviors of viscoelastic axially functionally graded material(AFG)pipes conveying pulsating internal flow are very complex.And the dynamic behavior will induce the failure of the pipes,and resea...The nonlinear dynamic behaviors of viscoelastic axially functionally graded material(AFG)pipes conveying pulsating internal flow are very complex.And the dynamic behavior will induce the failure of the pipes,and research of vibration and stability of pipes becomes a major concern.Considering that the elastic modulus,density,and coefficient of viscoelastic damping of the pipe material vary along the axial direction,the transverse vibration equation of the viscoelastic AFG pipe conveying pulsating fluid is established based on the Euler-Bernoulli beam theory.The generalized integral transform technique(GITT)is used to transform the governing fourth-order partial differential equation into a nonlinear system of fourth-order ordinary differential equations in time.The time domain diagram,phase portraits,Poincarémap and power spectra diagram at different dimensionless pulsation frequencies,are discussed in detail,showing the characteristics of chaotic,periodic,and quasi-periodic motion.The results show that the distributions of the elastic modulus,density,and coefficient of viscoelastic damping have significant effects on the nonlinear dynamic behavior of the viscoelastic AFG pipes.With the increase of the material property coefficient k,the transition between chaotic,periodic,and quasi-periodic motion occurs,especially in the high-frequency region of the flow pulsation.展开更多
In supervised learning, the imbalanced number of instances among the classes in a dataset can make the algorithms to classify one instance from the minority class as one from the majority class. With the aim to solve ...In supervised learning, the imbalanced number of instances among the classes in a dataset can make the algorithms to classify one instance from the minority class as one from the majority class. With the aim to solve this problem, the KNN algorithm provides a basis to other balancing methods. These balancing methods are revisited in this work, and a new and simple approach of KNN undersampling is proposed. The experiments demonstrated that the KNN undersampling method outperformed other sampling methods. The proposed method also outperformed the results of other studies, and indicates that the simplicity of KNN can be used as a base for efficient algorithms in machine learning and knowledge discovery.展开更多
Lower efficiencies induce higher energy costs and pose a barrier to wave energy devices'commercial applications.Therefore,the efficiency enhancement of wave energy converters has received much attention in recent ...Lower efficiencies induce higher energy costs and pose a barrier to wave energy devices'commercial applications.Therefore,the efficiency enhancement of wave energy converters has received much attention in recent decades.The reported research presents the double snap-through mechanism applied to a hemispheric point absorber type wave energy converter(WEC)to improve the energy absorption perfomance.The double snap-through mechanism comprises four oblique springs mounted in an X-configuration.This provides the WEC with different dynamic stability behaviors depending on the particular geometric and physical parameters employed.The efficiency of these different WEC behaviors(linear,bistable,and tristable)was initially evaluated under the action of regular waves.The results for bistable or tristable responses indicated significant improvements in the WEC's energy capture efficiency.Furthermore,the WEC frequency bandwidth was shown to be significantly enlarged when the tristable mode was in operation.However,the corresponding tristable trajectory showed intra-well behavior in the middle potential well,which induced a more severe low-energy absorption when a small wave amplitude acted on the WEC compared to when the bistable WEC was employed.Nevertheless,positive effects were observed when appropriate initial conditions were imposed.The results also showed that for bistable or tristable responses,a suitable spring stiffness may cause the buoy to oscillate in high energy modes.展开更多
It is well known that no criterion about seismic design for risers is available, and relevant research has not been reported. A comprehensive study of riser dynamics during earthquakes is performed in this paper. A dy...It is well known that no criterion about seismic design for risers is available, and relevant research has not been reported. A comprehensive study of riser dynamics during earthquakes is performed in this paper. A dynamic model for seismic analysis of risers is developed in accordance with the working environment of the risers and the influence of inertia force of the pipelines. The dynamic equations for the developed model are derived and resolved on the basis of the energy theory of beams. Numerical simulation for an engineering project in the Bohai Oil Field, China shows that the fundamental frequency of the riser plays the major role in the seismic responses, and for platforms in shallow water in Bohai Bay, the risers demonstrate a much lower stress response due to prominent differences between the riser frequency and the earthquake wave frequency. The presented model and its corresponding method for seismic analysis are practical and important for riser design resistant to earthquake waves.展开更多
Based on the Euler-Bernoulli beam theory and Kelvin-Voigt model,a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established.The governin...Based on the Euler-Bernoulli beam theory and Kelvin-Voigt model,a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established.The governing partial differential equation is transformed into a nonlinear system of fourth-order ordinary differential equations by using the generalized integral transform technique(GITT).The effects of the combined excitation of base motion and pulsating internal flow on the nonlinear dynamic behavior of the pipe are investigated using a bifurcation diagram,phase trajectory diagram,power spectrum diagram,time-domain diagram,and Poincare map.The results show that the base excitation amplitude and frequency significantly affect the dynamic behavior of the pipe system.Some new resonance phenomena can be observed,such as the period-1 motion under the base excitation or the pulsating internal flow alone becomes the multi-periodic motion,quasi-periodic motion or even chaotic motion due to the combined excitation action.展开更多
AIM:To evaluate the potential use of colonoscopy and endoluminal ultrasonic biomicroscopy(eUBM)to track the progression of mouse colonic lesions.METHODS:Ten mice were treated with a single azoxy-methane intraperitonea...AIM:To evaluate the potential use of colonoscopy and endoluminal ultrasonic biomicroscopy(eUBM)to track the progression of mouse colonic lesions.METHODS:Ten mice were treated with a single azoxy-methane intraperitoneal injection(week 1)followed by seven days of a dextran sulfate sodium treatment in their drinking water(week 2)to induce inflammationassociated colon tumors.eUBM was performed simultaneously with colonoscopy at weeks 13,17-20 and21.A 3.6-F diameter 40 MHz mini-probe catheter was used for eUBM imaging.The ultrasound mini-probe catheter was inserted into the accessory channel of a pediatric flexible bronchofiberscope,allowing simultaneous acquisition of colonoscopic and eUBM images.During image acquisition,the mice were anesthetized with isoflurane and kept in a supine position over a stainless steel heated surgical waterbed at 37℃.Both eUBM and colonoscopic images were captured and stored when a lesion was detected by colonoscopy or when the eUBM image revealed a modified colon wall anatomy.During the procedure,the colon was irrigated with water that was injected through a flush port on the mini-probe catheter and that acted as the ultrasound coupling medium between the transducer and the colon wall.Once the acquisition of the last eUBM/colonoscopy section for each animal was completed,the colons were fixed,paraffin-embedded,and stained with hematoxylin and eosin.Colon images acquired at the first time-point for each mouse were compared with subsequent eUBM/colonoscopic images of the same sites obtained in the following acquisitions to evaluate lesion progression.RESULTS:All 10 mice had eUBM and colonoscopic images acquired at week 13(the first time-point).Two animals died immediately after the first imaging acquisition and,consequently,only 8 mice were subjected to the second eUBM/colonoscopy imaging acquisition(at the second time-point).Due to the advanced stage of colonic tumorigenesis,5 animals died after the second time-point image acquisition,and thus,only three were subjected to the third eUBM/colonoscopy imaging acquisition(the third time-point).eUBM was able to detect the four layers in healthy segments of colon:the mucosa(the first hyperechoic layer moving away from the mini-probe axis),followed by the muscularis mucosae(hypoechoic),the submucosa(the second hyperechoic layer)and the muscularis externa(the second hypoechoic layer).Hypoechoic regions between the mucosa and the muscularis externa layers represented lymphoid infiltrates,as confirmed by the corresponding histological images.Pedunculated tumors were represented by hyperechoic masses in the mucosa layer.Among the lesions that decreased in size between the first and third time-points,one of the lesions changed from a mucosal hyperplasia with ulceration at the top to a mucosal hyperplasia with lymphoid infiltrate and,finally,to small signs of mucosal hyperplasia and lymphoid infiltrate.In this case,while lesion regression and modification were observable in the eUBM images,colonoscopy was only able to detect the lesion at the first and second time-points,without the capacity to demonstrate the presence of lymphoid infiltrate.Regarding the lesions that increased in size,one of them started as a small elevation in the mucosa layer and progressed to a pedunculated tumor.In this case,while eUBM imaging revealed the lesion at the first time-point,colonoscopy was only able to detect it at the second time-point.All colonic lesions(tumors,lymphoid infiltrate and mucosal thickening)were identified by eUBM,while colonoscopy identified just76%of them.Colonoscopy identified all of the colonic tumors but failed to diagnose lymphoid infiltrates and increased mucosal thickness and failed to differentiate lymphoid infiltrates from small adenomas.During the observation period,most of the lesions(approximately67%)increased in size,approximately 14%remained unchanged,and 19%regressed.CONCLUSION:Combining eUBM with colonoscopy improves the diagnosis and the follow-up of mouse colonic lesions,adding transmural assessment of the bowel wall.展开更多
基金the support of EPIC—Energy Production Innovation Center,hosted by the University of Campinas(UNICAMP)sponsored by FAPESP—Sao Paulo Research Foundation(2017/15736—3 process)+2 种基金the support and funding from Equinor Brazil and the support of ANP(Brazil's National Oil,Natural Gas and Biofuels Agency)through the R&D levy regulationthe Center of Energy and Petroleum Studies(CEPETRO)the School of Mechanical Engineering(FEM)。
文摘This study investigates the impact of pore network characteristics on fluid flow through complex and heterogeneous porous media,providing insights into the factors affecting fluid propagation in such systems.Specifically,high-resolution or micro X-ray computed tomography(CT)imaging techniques were utilized to examine outcrop stromatolite samples of the Lagoa Salgada,considered flow analogous to the Brazilian Pre-salt carbonate reservoirs.The petrophysical results comprised two distinct stromatolite depositional facies,the columnar and the fine-grained facies.By generating pore network model(PNM),the study quantified the relationship between key features of the porous system,including pore and throat radius,throat length,coordination number,shape factor,and pore volume.The study found that the less dense pore network of the columnar sample is typically characterized by larger pores and wider and longer throats but with a weaker connection of throats to pores.Both facies exhibited less variability in the radius of the pores and throats in comparison to throat length.Additionally,a series of core flooding experiments coupled with medical CT scanning was designed and conducted in the plug samples to assess flow propagation and saturation fields.The study revealed that the heterogeneity and presence of disconnected or dead-end pores significantly impacted the flow patterns and saturation.Two-phase flow patterns and oil saturation distribution reveal a preferential and heterogeneous displacement that mainly swept displaced fluid in some regions of plugs and bypassed it in others.The relation between saturation profiles,porosity profiles,and the number of fluid flow patterns for the samples was evident.Only for the columnar plug sample was the enhancement in recovery factor after shifting to lower salinity water injection(SB)observed.
基金Project supported by the Science Foundation of China University of Petroleum in Beijing(No.2462013YJRC003)
文摘The generalized integral transform technique （GITT） is used to find a semianalytical numerical solution for dynamic response of an axially moving Timoshenko beam with clamped-clamped and simply-supported boundary conditions, respectively. The implementation of GITT approach for analyzing the forced vibration equation eliminates the space variable and leads to systems of second-order ordinary differential equations （ODEs） in time. The MATHEMATICA built-in function, NDSolve, is used to numerically solve the resulting transformed ODE system. The good convergence behavior of the suggested eigenfunction expansions is demonstrated for calculating the transverse deflection and the angle of rotation of the beam cross-section. Moreover, parametric studies are performed to analyze the effects of the axially moving speed, the axial tension, and the amplitude of external distributed force on the vibration amplitude of axially moving Timoshenko beams.
基金Brazilian Funding Agencies CNPq, CAPES, FAPERJ and MCT/INCTREAGEO provided the financial support to the present study
文摘This paper describes a three-dimensional(3D) numerical analysis of a test embankment on geotextileencased columns(GECs), in comparison with two-dimensional(2D) axisymmetric and plane strain analyses. The 3D numerical analysis was performed considering a rectangular strip under the embankment centerline. The 2D analysis was also carried out using axisymmetric unit cell and plane strain approaches.Numerical results indicated that the adopted 3D strip model represented well the measured deformations and pore pressure evolution during embankment construction and post-contraction periods.Unlike the unit cell model, both plane strain and 3D analyses could properly determine the settlement profile along the embankment base as well as the profile of the horizontal soil deformation beneath the embankment toes. The plane strain analysis, however, was not able to compute the geotextile ring force which might be simply calculated using the axisymmetric unit cell approach. The paper also showed that, due to horizontal boundary fixities applied to the embankment borders, the unit cell model clearly underestimated the tension developed in the basal geogrid.
基金supported by the National Natural Science Foundation of China (Grant No. 50979113)the National High Technology Research and Development Program of China (863 Program, Grant No. 2006AA09A105)the China National Offshore Oil Corporation
文摘As there are no specific guidelines on design of subsea pipelines crossing active seismic faults, methods for land buried pipelines have been applied to. Taking the large seismic fault movement into account, this paper proposes improved methods for seismic designs of subsea pipelines by comprehensively investigating the real constraining of soil on the pipelines, the interaction processes of soil with the pipeline, the plastic slippage of the soil, and the elastic-plastic properties of the pipeline materials. New formulas are given to calculate the length of transition section and its total elongation. These formulas are more reasonable in mechanism, and more practical for seismic design of subsea pipelines crossing active faults.
基金Supported by PETROBRAS, LabOceano/COPPE/UFRJ and CNPq
文摘The methodology to obtain the non-linear roll damping from decay tests is very old. It has been proposed by Froude in the 19th century and used from then on. Behind it there is a quadratic model [θ｜θ｜] for the damping and a subsequent equivalent linearization. Probably all model basin in the world follows this approach to assess the damping from a methods to get the P1-P2 coefficients. This is very applied to any kind of hull. However, it has become decay test. This is well documented and so is the general in the sense that in principle, it could be clear that for hull with a flat bottom such as a very large crude carrier （VLCC）, this approach may lead to confusing results such as negative P2. Faced with this, the work presents a completely new idea. Avoiding the polynomial approximation, the basic attitude is to devise two regions from the decaying test response. The first, called the large amplitude response region yields a larger damping, probably due to the large bilge keel vortices that are attracted to the hull flat bottom. The second is the small amplitude response region where the vortices are not attracted to the bottom but travels approximately 45° sidewise. These observations has led to a new approach called the bi-linear approach as discussed in the work after analyzing several （many） model test results. In fact, a new modified bi-linear approach is ultimately proposed after the understanding of a transition region instead of a transition angle.
基金supported by the National Natural Science Foundation of China(Grant No. 50979113)the High Technology Research and Development Program of China(863 Program,Grant No. 2006AA09A105)
文摘Along with the consumption increase of the petroleum products, more countries have transferred their attentions to the offshore fields, especially the deepwater oil and gas reserves. For deepwater exploitation, the risers must be installed to act as the conduits connecting surface platforms to subsea facilities. In this paper, the typical risers sorted by different classes are introduced, and the correspondent installation methods are presented. By investigating the recent projects performed in the deepwater hot spots, and combining the challenges of HYSY20 l for riser installation, a lifting device developed for assisting riser installation is proposed and detailed to satisfy the installation of deepwater risers in the LW3-1 Gas Field of 1500 m in the South China Sea. Tests on both the functions and performances of such a new system exhibit the satisfaction of meeting all challenging requirements of HYSY201 for application to riser installation in waters up to a depth of 3000 m in the South China Sea.
文摘Auto-thermal reforming of methane, combining partial oxidation and reforming of methane with CO2 or steam, was carried out with Pt/Al2O3, Pt/ZrO2 and Pt/CeO2 catalysts, in a temperature range of 300-900℃. The auto-thermal reforming occurs in two simultaneous stages, namely, total combustion of methane and reforming of the unconverted methane with steam and CO2, with the O2 conversion of 100% starting from 450℃. For combination with CO2 reforming, the Pt/CeO2 catalyst showed the lowest initial activity at 800℃, and the highest stability over 40 h on-stream. This catalyst also presented the best performance for the reaction with steam at 800℃. The higher resistance to coke formation of the catalyst supported on ceria is due to the metal-support interactions and the higher mobility of oxygen in the oxide lattice.
文摘The kinetics of the Fischer-Tropsch reaction over a Co/Nb2O5 catalyst in a fixed bed reactor was investigated experimentally. Experiments were carried out under isothermal and isobaric conditions （T=543 K, P=2.1 MPa） and under different conditions of several H2/CO feed molar ratio （0.49-4.79）, space velocities （0.2-3.8 h^-1）, mass of catalyst （0.3-1.5 g）, and CO conversion （10%-29%）. Synthesis gas conversion was measured and data were reduced to estimate the kinetic parameters for different Langmuir-Hinshelwood rate expressions. Differential and integral reactor models were used for the nonlinear regression of kinetics parameters. One of the rate equations could well explain the data. The hydrocarbon product distributions that were experimentally determined exhibited an unusual behavior, and a possible explanation was discussed.
基金the support from the company Shell Brasil Petroleo and FAPESP through the “Reserch Centre for Gas Innovation-RCGI”(Fapesp Proc.2014/50279-4),hosted by the University of Sao Paulo,and the strategic importance of the support given by ANP(Brazil’s National Oil,Natural Gas and Biofuels Agency)through the R&D levy regulation.
文摘This paper presents a proposal for an experimental salt cavern in offshore ultra-deep water for CO2 abatement,including the instrumentation plan and well conceptual design evaluated for carbon capture and storage(CCS)application.These studies are based on applied computational mechanics associated with field experimentation that has contributed to the technical feasibility of the underground potash mine at the State of Sergipe in Brazil.This knowhow allowed the stability analysis of several salt caverns for brine production at the State of Alagoas in Brazil and to the drilling through stratified thick layers of salt of the pre-salt reservoirs in Santos Basin.Now,this knowledge has been applied in the design of onshore and offshore salt caverns opened by dissolution for storage of natural gas and CO2.The geomechanical study,through the application of computational mechanics,of offshore giant salt caverns of 450 m high by 150 m in diameter,shows that one cavern can store about 4 billion Sm3 or 7.2 million tons of CO2.Before the construction of the giant cavern,which will be the first gas storage offshore in the world,it has been decided to develop an experimental one,with smaller size,to obtained field parameters.The experimental cavern will allow the calibration of parameters to be used in the structural integrity analysis of the cavern and well for storage of natural gas which is rich in CO2 under high pressure.
基金supported by the National Natural Science Foundation of China(52171288,51890914)the Key Research and Development Program of Shandong Province(Major Innovation Project)(2022CXGC020405)+3 种基金the National Ministry of Industry and Information Technology Innovation Special Project-Engineering Demonstration Application of Subsea Oil and Gas Production System-Subject 4“Research on Subsea Christmas Tree and Wellhead Offshore Testing Technology”[MC-201901-S01-04]the Fundamental Research Funds for the Central Universities(20CX02410A)the Development Fund of Shandong Key Laboratory of Oil&Gas Storage and Transportation SafetyCNPq,CAPES and FAPERJ of Brazil。
文摘The nonlinear dynamic behaviors of viscoelastic axially functionally graded material(AFG)pipes conveying pulsating internal flow are very complex.And the dynamic behavior will induce the failure of the pipes,and research of vibration and stability of pipes becomes a major concern.Considering that the elastic modulus,density,and coefficient of viscoelastic damping of the pipe material vary along the axial direction,the transverse vibration equation of the viscoelastic AFG pipe conveying pulsating fluid is established based on the Euler-Bernoulli beam theory.The generalized integral transform technique(GITT)is used to transform the governing fourth-order partial differential equation into a nonlinear system of fourth-order ordinary differential equations in time.The time domain diagram,phase portraits,Poincarémap and power spectra diagram at different dimensionless pulsation frequencies,are discussed in detail,showing the characteristics of chaotic,periodic,and quasi-periodic motion.The results show that the distributions of the elastic modulus,density,and coefficient of viscoelastic damping have significant effects on the nonlinear dynamic behavior of the viscoelastic AFG pipes.With the increase of the material property coefficient k,the transition between chaotic,periodic,and quasi-periodic motion occurs,especially in the high-frequency region of the flow pulsation.
文摘In supervised learning, the imbalanced number of instances among the classes in a dataset can make the algorithms to classify one instance from the minority class as one from the majority class. With the aim to solve this problem, the KNN algorithm provides a basis to other balancing methods. These balancing methods are revisited in this work, and a new and simple approach of KNN undersampling is proposed. The experiments demonstrated that the KNN undersampling method outperformed other sampling methods. The proposed method also outperformed the results of other studies, and indicates that the simplicity of KNN can be used as a base for efficient algorithms in machine learning and knowledge discovery.
基金supported by the China Scholarship Council under Grant No.201600090258the National Key Research and Development Program of China under Grant No.2016YFC0303700the 111 Project under Grant No.B18054。
文摘Lower efficiencies induce higher energy costs and pose a barrier to wave energy devices'commercial applications.Therefore,the efficiency enhancement of wave energy converters has received much attention in recent decades.The reported research presents the double snap-through mechanism applied to a hemispheric point absorber type wave energy converter(WEC)to improve the energy absorption perfomance.The double snap-through mechanism comprises four oblique springs mounted in an X-configuration.This provides the WEC with different dynamic stability behaviors depending on the particular geometric and physical parameters employed.The efficiency of these different WEC behaviors(linear,bistable,and tristable)was initially evaluated under the action of regular waves.The results for bistable or tristable responses indicated significant improvements in the WEC's energy capture efficiency.Furthermore,the WEC frequency bandwidth was shown to be significantly enlarged when the tristable mode was in operation.However,the corresponding tristable trajectory showed intra-well behavior in the middle potential well,which induced a more severe low-energy absorption when a small wave amplitude acted on the WEC compared to when the bistable WEC was employed.Nevertheless,positive effects were observed when appropriate initial conditions were imposed.The results also showed that for bistable or tristable responses,a suitable spring stiffness may cause the buoy to oscillate in high energy modes.
基金supported by the National Natural Science Foundation of China (granted number 50979113)funded by the National 863 Program of China (granted number 2006AA09A105)
文摘It is well known that no criterion about seismic design for risers is available, and relevant research has not been reported. A comprehensive study of riser dynamics during earthquakes is performed in this paper. A dynamic model for seismic analysis of risers is developed in accordance with the working environment of the risers and the influence of inertia force of the pipelines. The dynamic equations for the developed model are derived and resolved on the basis of the energy theory of beams. Numerical simulation for an engineering project in the Bohai Oil Field, China shows that the fundamental frequency of the riser plays the major role in the seismic responses, and for platforms in shallow water in Bohai Bay, the risers demonstrate a much lower stress response due to prominent differences between the riser frequency and the earthquake wave frequency. The presented model and its corresponding method for seismic analysis are practical and important for riser design resistant to earthquake waves.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52171288,51890914)the Key Research and Development Program of Shandong Province(Major Innovation Project)(Grant No.2022CXGC020405)+1 种基金the National Ministry of Industry and Information Technology Innovation Special Project-Engineering Demonstration Application of Subsea Oil and Gas Production SystemSubject 4:Research on Subsea Christmas Tree and Wellhead Offshore Testing Technology(Grant No.MC-201901-S01-04)CNPq,CAPES and FAPERJ of Brazil。
文摘Based on the Euler-Bernoulli beam theory and Kelvin-Voigt model,a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established.The governing partial differential equation is transformed into a nonlinear system of fourth-order ordinary differential equations by using the generalized integral transform technique(GITT).The effects of the combined excitation of base motion and pulsating internal flow on the nonlinear dynamic behavior of the pipe are investigated using a bifurcation diagram,phase trajectory diagram,power spectrum diagram,time-domain diagram,and Poincare map.The results show that the base excitation amplitude and frequency significantly affect the dynamic behavior of the pipe system.Some new resonance phenomena can be observed,such as the period-1 motion under the base excitation or the pulsating internal flow alone becomes the multi-periodic motion,quasi-periodic motion or even chaotic motion due to the combined excitation action.
基金Supported by National Council for Scientific and Technological Development(CNPq)Brazilian Federal Agency for Support and Evaluation of Higher Education(CAPES) and Carlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro(FAPERJ)
文摘AIM:To evaluate the potential use of colonoscopy and endoluminal ultrasonic biomicroscopy(eUBM)to track the progression of mouse colonic lesions.METHODS:Ten mice were treated with a single azoxy-methane intraperitoneal injection(week 1)followed by seven days of a dextran sulfate sodium treatment in their drinking water(week 2)to induce inflammationassociated colon tumors.eUBM was performed simultaneously with colonoscopy at weeks 13,17-20 and21.A 3.6-F diameter 40 MHz mini-probe catheter was used for eUBM imaging.The ultrasound mini-probe catheter was inserted into the accessory channel of a pediatric flexible bronchofiberscope,allowing simultaneous acquisition of colonoscopic and eUBM images.During image acquisition,the mice were anesthetized with isoflurane and kept in a supine position over a stainless steel heated surgical waterbed at 37℃.Both eUBM and colonoscopic images were captured and stored when a lesion was detected by colonoscopy or when the eUBM image revealed a modified colon wall anatomy.During the procedure,the colon was irrigated with water that was injected through a flush port on the mini-probe catheter and that acted as the ultrasound coupling medium between the transducer and the colon wall.Once the acquisition of the last eUBM/colonoscopy section for each animal was completed,the colons were fixed,paraffin-embedded,and stained with hematoxylin and eosin.Colon images acquired at the first time-point for each mouse were compared with subsequent eUBM/colonoscopic images of the same sites obtained in the following acquisitions to evaluate lesion progression.RESULTS:All 10 mice had eUBM and colonoscopic images acquired at week 13(the first time-point).Two animals died immediately after the first imaging acquisition and,consequently,only 8 mice were subjected to the second eUBM/colonoscopy imaging acquisition(at the second time-point).Due to the advanced stage of colonic tumorigenesis,5 animals died after the second time-point image acquisition,and thus,only three were subjected to the third eUBM/colonoscopy imaging acquisition(the third time-point).eUBM was able to detect the four layers in healthy segments of colon:the mucosa(the first hyperechoic layer moving away from the mini-probe axis),followed by the muscularis mucosae(hypoechoic),the submucosa(the second hyperechoic layer)and the muscularis externa(the second hypoechoic layer).Hypoechoic regions between the mucosa and the muscularis externa layers represented lymphoid infiltrates,as confirmed by the corresponding histological images.Pedunculated tumors were represented by hyperechoic masses in the mucosa layer.Among the lesions that decreased in size between the first and third time-points,one of the lesions changed from a mucosal hyperplasia with ulceration at the top to a mucosal hyperplasia with lymphoid infiltrate and,finally,to small signs of mucosal hyperplasia and lymphoid infiltrate.In this case,while lesion regression and modification were observable in the eUBM images,colonoscopy was only able to detect the lesion at the first and second time-points,without the capacity to demonstrate the presence of lymphoid infiltrate.Regarding the lesions that increased in size,one of them started as a small elevation in the mucosa layer and progressed to a pedunculated tumor.In this case,while eUBM imaging revealed the lesion at the first time-point,colonoscopy was only able to detect it at the second time-point.All colonic lesions(tumors,lymphoid infiltrate and mucosal thickening)were identified by eUBM,while colonoscopy identified just76%of them.Colonoscopy identified all of the colonic tumors but failed to diagnose lymphoid infiltrates and increased mucosal thickness and failed to differentiate lymphoid infiltrates from small adenomas.During the observation period,most of the lesions(approximately67%)increased in size,approximately 14%remained unchanged,and 19%regressed.CONCLUSION:Combining eUBM with colonoscopy improves the diagnosis and the follow-up of mouse colonic lesions,adding transmural assessment of the bowel wall.
