Through a modified inherent strain model based on the minimum residual stress and deformation,three building schemes with different building postures and support structures were evaluated by finite element analysis.Re...Through a modified inherent strain model based on the minimum residual stress and deformation,three building schemes with different building postures and support structures were evaluated by finite element analysis.Results demonstrate that according to the principle of reducing the overall height of the building and reducing the support structure with a large tilt angle from the building direction,the residual stress and deformation can be effectively reduced by proper design of building posture and support before laser powder bed melting.Moreover,without the data of thermophysical property variation of Ti-6Al-4V artificial knee implants with temperature,predicting the residual stress and deformation with acceptable accuracy and reduced time cost can be achieved by the inherent strain model.展开更多
Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties.Such non-monotonic responses can significantly impact the stability analysis and design of...Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties.Such non-monotonic responses can significantly impact the stability analysis and design of overlying shallow foundations.In this study,the undrained bearing capacity of shallow foundations resting on inhomogeneous and anisotropic clay layers subjected to oblique-eccentric combined loading is investigated through a comprehensive series of finite element limit analysis(FELA)based on the well-established lower-bound theorem and second-order cone programming(SOCP).The heterogeneity of normally consolidated(NC)clays is simulated by adopting a well-known general model of undrained shear strength increasing linearly with depth.In contrast,for overconsolidated(OC)clays,the variation of undrained shear strength with depth is considered to follow a bilinear trend.Furthermore,the inherent anisotropy is accounted for by adopting different values of undrained shear strength along different directions within the soil medium,employing an iterative-based algorithm.The results of numerical simulations are utilized to investigate the influences of natural soil heterogeneity and inherent anisotropy on the ultimate bearing capacity,failure envelope,and failure mechanism of shallow foundations subjected to the various combinations of vertical-horizontal(V-H)and vertical-moment(V-M)loads.展开更多
Sodium alginate(SA)is generally considered highly hydrophilic due to two hydroxyl groups and a carboxylate group on each pyranose ring.However,SA will form a gel after dissolving in water for a certain period.The two ...Sodium alginate(SA)is generally considered highly hydrophilic due to two hydroxyl groups and a carboxylate group on each pyranose ring.However,SA will form a gel after dissolving in water for a certain period.The two properties of SA,hydrophilicity and gelation,seem to be paradoxical.In this study,to explore the mechanism behind these paradoxical properties,the single-chain behaviors of SA in various liquid environments have been investigated by using single-molecule force spectroscopy(SMFS).In nonpolar solvents such as nonane,SA exhibits its single-chain inherent elasticity consistent with the theoretical elasticity derived from quantum mechanical(QM)calculations.Notably,the experimental curve of SA obtained in water shows a long plateau in the low force region.Further research reveals that this phenomenon is driven by the hydrophobic effect.Additionally,SA shows greater rigidity than its inherent elasticity in the middle and high force regions due to electrostatic repulsion between carboxylate groups on adjacent sugar rings.Comparative single-molecule studies suggest that SA exhibits considerable hydrophobicity,offering new insights into the gelation process in water.展开更多
Large-scale and heavily jointed rocks have inherent planes of anisotropy and secondary structural planes,such as dominant joint sets and random fractures,which result in significant differences in their failure mechan...Large-scale and heavily jointed rocks have inherent planes of anisotropy and secondary structural planes,such as dominant joint sets and random fractures,which result in significant differences in their failure mechanism and deformation behavior compared to other rock types.To address this issue,inherent anisotropic rocks with large-scale and dense joints are considered to be composed of the rock matrix,inherent planes of anisotropy,and secondary structural planes.Then a new implicit continuum model called LayerDFN is developed based on the crack tensor and damage tensor theories to characterize the mechanical properties of inherent anisotropic rocks.Furthermore,the LayerDFN model is implemented in the FLAC3D software,and a series of numerical results for typical example problems is compared with those obtained from the 3DEC,the analytical solutions,similar classical models,laboratory uniaxial compression tests,and field rigid bearing plate tests.The results demonstrate that the LayerDFN model can effectively capture the anisotropic mechanical properties of inherent anisotropic rocks,and can quantitatively characterize the damaging effect of the secondary structural planes.Overall,the numerical method based on the LayerDFN model provides a comprehensive and reliable approach for describing and analyzing the behavior of inherent anisotropic rocks,which will provide valuable insights for engineering design and decision-making processes.展开更多
The mechanical properties of stratified rocks are closely related not only to the stress state but also to the inherent structural anisotropy,which can be represented by the occurrence of bedding planes.This research ...The mechanical properties of stratified rocks are closely related not only to the stress state but also to the inherent structural anisotropy,which can be represented by the occurrence of bedding planes.This research aims to enhance the understanding of the anisotropic deformation and failure behaviors of stratified rocks by proposing a novel coupled elastoplastic-damage constitutive model.In this constitutive model,a scalar anisotropic parameter(stress-structure mixed invariant)based on the Pietruszczak–Mroz anisotropic theory is incorporated into a nonlinear yield surface,which accounts for the combined effects of the stress state and bedding structure on the anisotropic strength behaviors of stratified rocks.A damage-driven function governs the expansion and contraction of the anisotropic yield surface in the pre-peak strain hardening and post-peak strain-softening regions.The strength and deformation characteristics under multiaxial stress conditions are represented by incorporating the Lode's angle into the yield and plastic potential functions.Numerical simulations are conducted to facilitate a comparison with the conventional and true triaxial compression test data for several stratified rocks.The simulation results demonstrate good agreement with the test data,validating the effectiveness of the proposed constitutive model.This study provides theoretical and technical support for addressing engineering challenges involving stratified rocks.展开更多
This paper presents a method for estimating the parameters of DC-link capacitors in three-level NPC voltage source inverters(3L-NPC-VSI)used in grid-tied systems.The technique uses the signals generated by the intermo...This paper presents a method for estimating the parameters of DC-link capacitors in three-level NPC voltage source inverters(3L-NPC-VSI)used in grid-tied systems.The technique uses the signals generated by the intermodulation caused by the PWM strategy and converter topology interaction to estimate the capacitor parameters of the converter DC-link.It utilizes an observer-based structure consisting of a recursive noninteger sliding discrete Fourier transform(rnSDFT)and an RLS filter improved with a forgetting factor(oSDFT-RLS)to accurately estimate the capacitance and equivalent series resistance(ESR).Importantly,this method does not require additional sensors beyond those already installed in off-the-shelf 3L-NPC-VSI systems,ensuring its noninvasiveness.Furthermore,the oSDFTRLS estimates capacitor parameters in the time-frequency domain,enabling the tracking of capacitor degradation and predicting potential faults.Experimental results from the laboratory setup demonstrate the effectiveness of the proposed condition monitoring method.展开更多
This thesis takes the Skopostheorie as the guiding principle,analyzes and explains some important yet tend-to-be neglected standards,that is,the inherent characteristics unique to each product or service category.By m...This thesis takes the Skopostheorie as the guiding principle,analyzes and explains some important yet tend-to-be neglected standards,that is,the inherent characteristics unique to each product or service category.By means of analyzing cases,either successful or undesirable,it suggests the brand name translation had better imply their underlying features.Such principles may result in amazing translations.展开更多
Electrochemical water splitting is regarded as the most promising approach to produce hydrogen.However,the sluggish electrochemical reactions occurring at the anode and cathode,namely,the oxygen evolution reaction(OER...Electrochemical water splitting is regarded as the most promising approach to produce hydrogen.However,the sluggish electrochemical reactions occurring at the anode and cathode,namely,the oxygen evolution reaction(OER)and the hydrogen evolution reaction(HER),respectively,consume a tremendous amount of energy,seriously hampering its wide application.Recently,single-atom catalysts(SACs)have been proposed to effectively enhance the kinetics of these two reactions.In this minireview,we focus on the recent progress in SACs for OER and HER applications.Three classes of SACs have been reviewed,i.e.,alloy-based SACs,carbon-based SACs and SACs supported on other compounds.Different factors affecting the activities of SACs are also highlighted,including the inherent element property,the coordination environment,the geometric structure and the loading amount of metal atoms.Finally,we summarize the current problems and directions for future development in SACs.展开更多
Understanding the size effect exhibited by the fracture mechanism of anisotropic geomaterials is important for engineering practice. In this study, the anisotropic features of the nominal strength, apparent fracture t...Understanding the size effect exhibited by the fracture mechanism of anisotropic geomaterials is important for engineering practice. In this study, the anisotropic features of the nominal strength, apparent fracture toughness, effective fracture energy and fracture process zone(FPZ) size of geomaterials were first analyzed by systematic size effect fracture experiments. The results showed that the nominal strength and the apparent fracture toughness decreased with increasing bedding plane inclination angle.The larger the specimen size was, the smaller the nominal strength and the larger the apparent fracture toughness was. When the bedding inclination angle increased from 0° to 90°, the effective fracture energy and the effective FPZ size both first decreased and then increased within two complex variation stages that were bounded by the 45° bedding angle. Regardless of the inherent anisotropy of geomaterials,the nominal strength and apparent fracture toughness can be predicted by the energy-based size effect law, which demonstrates that geomaterials have obvious quasi-brittle characteristics. Theoretical analysis indicated that the true fracture toughness and energy dissipation can be calculated by linear elastic fracture mechanics only when the brittleness number is higher than 10;otherwise, size effect tests should be adopted to determine the fracture parameters.展开更多
The Changjiang （Yangtze） Estuary is located in the East China Sea shelf with shallow water. Affected by the tide mixing and the runoff of the Changjiang River and the Qiantang River the turbidity is very high. Gener...The Changjiang （Yangtze） Estuary is located in the East China Sea shelf with shallow water. Affected by the tide mixing and the runoff of the Changjiang River and the Qiantang River the turbidity is very high. Generally, the water-leaving radiance is high in the turbid water because of the large particle scattering. Based on the in-situ data and ocean color remote sensing data of SeaWiFS, it was found that there was a black water region with the normalized water-leaving radiances less than 0.5 mW/（cm2-μm2-sr）. The optical principle of the occurrence of this black water was analyzed by the inherent optical properties and the ocean color components. The results show that black water is caused by the relative low values of the suspended particle matter concentration and the back scattering ratio. In the black water region, the percentage of the phytoplankton absorption was relatively high, and the large size of the phytoplankton caused the low value of the particle backscattering ratio.展开更多
Tendon force is an essential concept to predict welding distortion such as longitudinal shrinkage and welding induced buckling in thin plate fabrication. In this study,three approaches with experimental,theoretical an...Tendon force is an essential concept to predict welding distortion such as longitudinal shrinkage and welding induced buckling in thin plate fabrication. In this study,three approaches with experimental,theoretical and computational analysis,are examined to evaluate the magnitude of tendon force. In detail,inherent deformation theory is introduced first,the theoretical analysis to obtain the inherent strain solution is also reviewed; and then analytical solution for tendon force is achieved. Also,the theory of FE analysis for welding is introduced and implemented in a computation to obtain the transient temperature distribution,plastic strain,residual stress and welding distortion in a bead-on-plate welded joint with 2. 28 mm in thickness. The longitudinal displacement is employed to evaluate tendon force directly,and these computed inherent strain and inherent stress can also be employed to evaluate tendon force by integration approach later. All the evaluated magnitudes of tendon force have a good agreement with each other.展开更多
We tested and modified the quasi-analytical algorithm （QAA） using 57 groups of field data collected in the spring of 2003 in the Yellow Sea and East China Sea. The QAA performs well in deriving total absorption coef...We tested and modified the quasi-analytical algorithm （QAA） using 57 groups of field data collected in the spring of 2003 in the Yellow Sea and East China Sea. The QAA performs well in deriving total absorption coefficients of typical coastal waters. The average percentage difference （APD） is in a range of 13.9%-38.5% for the total absorption coefficient （13.9% at 440 nm）, and differences in particle backscattering coefficient bbp（2） are less than 50% （in the case of the updated QAA）. To obtain improved results, we modified the QAA by adjusting the empirical relationships. The modified algorithm is then applied to the field data to test its performance. The APDs were 44.7%-46.6% for bbp（λ） and 9.9%-32.8% （9.9% at 555 nm） for the total absorption coefficient. This indicates that the modified QAA derives better results. We also used the modified model to derive phytoplankton pigment absorption （aph） and detritus and CDOM absorption （aug） coefficients. The APDs for aph and a dg at 440 nm are 37.1% and 19.8%. In this paper, we discuss error sources using the measured dataset. More independent field data can improve this algorithm and derive better results.展开更多
With a growing population, an increasing number of petrochemical facilities are built with larger capacity and more complexity, which pose a great risk to assets, community and environment. The value of inherently saf...With a growing population, an increasing number of petrochemical facilities are built with larger capacity and more complexity, which pose a great risk to assets, community and environment. The value of inherently safer design is recognized with time by all stakeholders, and an effective tool is needed to evaluate and compare inherent safety of alternative technologies. This study developed a safety index to evaluate existing technologies for their safety levels and guide inherently safer design. The Integrated Risk-based Safety Index(IRSI) was developed based on a comprehensive review of petrochemical processes, incident cases from Sinopec and US Chemical Safety Board, and existing safety index systems. The IRSI included all major hazards, including fire, explosion,toxic release, dust explosion, physical explosion, and runaway. Also, the integrated life cycle approach considered chemical hazards, equipment failure rates and safety measures in this risk-based index. Advanced modeling techniques, PHAST simulation and Neural Network, were used in the development of three novel sub-indices in the projects, fire, explosion and toxic release. The index system could be easily incorporated into a user friendly tool for the ease of application. A case study of hydrogen dioxide was conducted using the IRSI, which showed its capability for evaluating the safety level of process facilities.展开更多
Welding deformations can be predicted by inherent strains that are assumed to be distributed in the welds and nearby area. This method is more convenient compared with the thermo elasto plastic finite element method b...Welding deformations can be predicted by inherent strains that are assumed to be distributed in the welds and nearby area. This method is more convenient compared with the thermo elasto plastic finite element method because only elastic analysis is necessary. The problem is how to know the inherent strains in advance during deformation analysis. The relations between inherent strains and welding parameters based on some experimental curves and a 3 D FEM model were introduced. According to this study, the longitudinal and transverse inherent strains that are the most important factors on welding deformations can be determined. The effectiveness of the proposed methods is demonstrated through the deformation analysis of a large welded cylinder with multipass welds as an example.展开更多
Digraph-based causal models have been widely used to model the cause and effect behavior of process systems. Signed digraphs （SDG） capture the direction of the effect. It should be mentioned that there are loops in ...Digraph-based causal models have been widely used to model the cause and effect behavior of process systems. Signed digraphs （SDG） capture the direction of the effect. It should be mentioned that there are loops in SDG generated from chemical process. From the point of the inherent operability, the worst unsafe factor is the SDG having positive loops that means any disturbance occurring within the loop will propagate through the nodes one by one and are amplified gradually, so the system may lose control, which may lead to an accident. So finding the positive loops in a SDG and treating these unsafe factors in a proper manner can improve the inherent safety of a chemical process. This article proposed a method that can detect the above-mentioned unsafe factors in the proc- ess conceptual design stage automatically through the analysis of the SDG generated from the chemical process. A case study is illustrated to show the working of the algorithm, and then a complicated case from industry is studied to depict the effectiveness of the proposed algorithm.展开更多
A potential energy framework for assessment of grid vulnerability was presented.In the framework,the branch potential energy function model was constructed.Two indexes,current vulnerability and forecasting vulnerabili...A potential energy framework for assessment of grid vulnerability was presented.In the framework,the branch potential energy function model was constructed.Two indexes,current vulnerability and forecasting vulnerability,were calculated.The current vulnerability was used to identify the current vulnerable area through calculating the distance between the current transmitted power and initial transmitted power;and the forecast vulnerability under variation of power injection was used to predict the vulnerable area of next step and verify the current vulnerable area.Numerical simulation was performed under variant operating conditions with IEEE-30 bus system,which shows that almost area of 90% overlaps between current vulnerable area and forecasting vulnerable area,the overlapped area is termed as inherent vulnerable area of grid.When considering N-1 contingency,the assessment results of this method proposed agree with those of optimal power flow.When considering N-2 contingency,optimal power flow fails to obtain correct results,while the method based on energy framework gives reliable results.展开更多
Strengthening and toughening mechanisms in composite ceramics is complex. A change in a single parameter induces multiple property variations. The multiple changes in properties are often incompletely represented in t...Strengthening and toughening mechanisms in composite ceramics is complex. A change in a single parameter induces multiple property variations. The multiple changes in properties are often incompletely represented in theoretical models. This incompleteness in the parameter chosen fails to explain the mechanism of failure in composite ceramics. The exponential toughness function is used to represent the pull-out toughening mechanism, which dominates the crack growth resistance curve（R-curve）. The strengthening-toughening model is established based on the Mori-Tanaka method（M-T method）. The influence of inherent defects on toughness function and strength is analyzed by using this model. The theoretical result is compared with the experiment data. This model exactly reflects the change in strength. The theoretical result indicates that defects change the toughness function. Moreover, micro-cracks increase toughness size ac, and the strength of crack instable extensions acutely decreases as defect content increases. This presented model establishes the relationship among the important mechanical parameters of defect, strength, elastic modulus, and the R-curve.展开更多
Layered two-dimensional(2 D)materials have received tremendous attention due to their unique physical and chemical properties when downsized to single or few layers.Several types of layered materials,especially transi...Layered two-dimensional(2 D)materials have received tremendous attention due to their unique physical and chemical properties when downsized to single or few layers.Several types of layered materials,especially transition metal dichalcogenides(TMDs)have been demonstrated to be good electrode materials due to their interesting physical and chemical properties.Apart from TMDs,post-transition metal chalcogenides(PTMCs)recently have emerged as a family of important semiconducting materials for electrochemical studies.PTMCs are layered materials which are composed of post-transition metals raging from main group IIIA to group VA(Ga,In,Ge,Sn,Sb and Bi)and group VI chalcogen atoms(S,selenium(Se)and tellurium(Te)).Although a large number of literatures have reviewed the electrochemical and electrocatalytic applications of TMDs,less attention has been focused on PTMCs.In this review,we focus our attention on PTMCs with the aim to provide a summary to describe their fundamental electrochemical properties and electrocatalytic activity towards hydrogen evolution reaction(HER).The characteristic chemical compositions and crystal structures of PTMCs are firstly discussed,which are different from TMDs.Then,inherent electrochemistry of PTMCs is discussed to unveil the well-defined redox behaviors of PTMCs,which could potentially affect their efficiency when applied as electrode materials.Following,we focus our attention on electrocatalytic activity of PTMCs towards HER including novel synthetic strategies developed for the optimization of their HER activity.This review ends with the perspectives for the future research direction in the field of PTMC based electrocatalysts.展开更多
Fracture data of both parent metal and weldment metals from surface cracked tensile plates made of 2219-T87 Al alloy at cryogenic temperatures were correlated using a modified inherent flaw model. Fracture parameters ...Fracture data of both parent metal and weldment metals from surface cracked tensile plates made of 2219-T87 Al alloy at cryogenic temperatures were correlated using a modified inherent flaw model. Fracture parameters to generate the failure assessment diagram were determined for the material. Fracture analysis was carried out considering the ultimate tensile strength value and the fracture data of aluminium base metal and weldment metal generated from center–surface cracked tensile specimens having different thicknesses. The failure assessment diagram of a material generated from tensile fracture plate configuration can be applied to failure pressure estimation of any cracked component, made of the same material.展开更多
基金Natural Science Foundation of Shandong Province(ZR2020ME020)。
文摘Through a modified inherent strain model based on the minimum residual stress and deformation,three building schemes with different building postures and support structures were evaluated by finite element analysis.Results demonstrate that according to the principle of reducing the overall height of the building and reducing the support structure with a large tilt angle from the building direction,the residual stress and deformation can be effectively reduced by proper design of building posture and support before laser powder bed melting.Moreover,without the data of thermophysical property variation of Ti-6Al-4V artificial knee implants with temperature,predicting the residual stress and deformation with acceptable accuracy and reduced time cost can be achieved by the inherent strain model.
文摘Clay deposits typically exhibit significant degrees of heterogeneity and anisotropy in their strength and stiffness properties.Such non-monotonic responses can significantly impact the stability analysis and design of overlying shallow foundations.In this study,the undrained bearing capacity of shallow foundations resting on inhomogeneous and anisotropic clay layers subjected to oblique-eccentric combined loading is investigated through a comprehensive series of finite element limit analysis(FELA)based on the well-established lower-bound theorem and second-order cone programming(SOCP).The heterogeneity of normally consolidated(NC)clays is simulated by adopting a well-known general model of undrained shear strength increasing linearly with depth.In contrast,for overconsolidated(OC)clays,the variation of undrained shear strength with depth is considered to follow a bilinear trend.Furthermore,the inherent anisotropy is accounted for by adopting different values of undrained shear strength along different directions within the soil medium,employing an iterative-based algorithm.The results of numerical simulations are utilized to investigate the influences of natural soil heterogeneity and inherent anisotropy on the ultimate bearing capacity,failure envelope,and failure mechanism of shallow foundations subjected to the various combinations of vertical-horizontal(V-H)and vertical-moment(V-M)loads.
基金financially supported by the National Natural Science Foundation of China(No.22273079)。
文摘Sodium alginate(SA)is generally considered highly hydrophilic due to two hydroxyl groups and a carboxylate group on each pyranose ring.However,SA will form a gel after dissolving in water for a certain period.The two properties of SA,hydrophilicity and gelation,seem to be paradoxical.In this study,to explore the mechanism behind these paradoxical properties,the single-chain behaviors of SA in various liquid environments have been investigated by using single-molecule force spectroscopy(SMFS).In nonpolar solvents such as nonane,SA exhibits its single-chain inherent elasticity consistent with the theoretical elasticity derived from quantum mechanical(QM)calculations.Notably,the experimental curve of SA obtained in water shows a long plateau in the low force region.Further research reveals that this phenomenon is driven by the hydrophobic effect.Additionally,SA shows greater rigidity than its inherent elasticity in the middle and high force regions due to electrostatic repulsion between carboxylate groups on adjacent sugar rings.Comparative single-molecule studies suggest that SA exhibits considerable hydrophobicity,offering new insights into the gelation process in water.
基金supported by financial support from the National Natural Science Foundation of China(Grant Nos.52309122 and U2340229)the Innovation Team of Changjiang River Scientific Research Institute(Grant No.CKSF2024329/YT).
文摘Large-scale and heavily jointed rocks have inherent planes of anisotropy and secondary structural planes,such as dominant joint sets and random fractures,which result in significant differences in their failure mechanism and deformation behavior compared to other rock types.To address this issue,inherent anisotropic rocks with large-scale and dense joints are considered to be composed of the rock matrix,inherent planes of anisotropy,and secondary structural planes.Then a new implicit continuum model called LayerDFN is developed based on the crack tensor and damage tensor theories to characterize the mechanical properties of inherent anisotropic rocks.Furthermore,the LayerDFN model is implemented in the FLAC3D software,and a series of numerical results for typical example problems is compared with those obtained from the 3DEC,the analytical solutions,similar classical models,laboratory uniaxial compression tests,and field rigid bearing plate tests.The results demonstrate that the LayerDFN model can effectively capture the anisotropic mechanical properties of inherent anisotropic rocks,and can quantitatively characterize the damaging effect of the secondary structural planes.Overall,the numerical method based on the LayerDFN model provides a comprehensive and reliable approach for describing and analyzing the behavior of inherent anisotropic rocks,which will provide valuable insights for engineering design and decision-making processes.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52109143 and 12062026)the Open Research Fund of State Key Laboratory of Simulation and Regulation of Water Cycle in River Basin(China Institute of Water Resources and Hydropower Research)(Grant No.IWHRSKL-KF202305).
文摘The mechanical properties of stratified rocks are closely related not only to the stress state but also to the inherent structural anisotropy,which can be represented by the occurrence of bedding planes.This research aims to enhance the understanding of the anisotropic deformation and failure behaviors of stratified rocks by proposing a novel coupled elastoplastic-damage constitutive model.In this constitutive model,a scalar anisotropic parameter(stress-structure mixed invariant)based on the Pietruszczak–Mroz anisotropic theory is incorporated into a nonlinear yield surface,which accounts for the combined effects of the stress state and bedding structure on the anisotropic strength behaviors of stratified rocks.A damage-driven function governs the expansion and contraction of the anisotropic yield surface in the pre-peak strain hardening and post-peak strain-softening regions.The strength and deformation characteristics under multiaxial stress conditions are represented by incorporating the Lode's angle into the yield and plastic potential functions.Numerical simulations are conducted to facilitate a comparison with the conventional and true triaxial compression test data for several stratified rocks.The simulation results demonstrate good agreement with the test data,validating the effectiveness of the proposed constitutive model.This study provides theoretical and technical support for addressing engineering challenges involving stratified rocks.
基金funded by the Brazilian National Council for Scientific and Technological Development—CNPq(CNPq grant number 405997/2022-1)supported by the EMBRAPII VIRTUS Competence Center in Intelligent Hardware for Industry—VIRTUS-CC(MCTI grant number 055/2023).
文摘This paper presents a method for estimating the parameters of DC-link capacitors in three-level NPC voltage source inverters(3L-NPC-VSI)used in grid-tied systems.The technique uses the signals generated by the intermodulation caused by the PWM strategy and converter topology interaction to estimate the capacitor parameters of the converter DC-link.It utilizes an observer-based structure consisting of a recursive noninteger sliding discrete Fourier transform(rnSDFT)and an RLS filter improved with a forgetting factor(oSDFT-RLS)to accurately estimate the capacitance and equivalent series resistance(ESR).Importantly,this method does not require additional sensors beyond those already installed in off-the-shelf 3L-NPC-VSI systems,ensuring its noninvasiveness.Furthermore,the oSDFTRLS estimates capacitor parameters in the time-frequency domain,enabling the tracking of capacitor degradation and predicting potential faults.Experimental results from the laboratory setup demonstrate the effectiveness of the proposed condition monitoring method.
文摘This thesis takes the Skopostheorie as the guiding principle,analyzes and explains some important yet tend-to-be neglected standards,that is,the inherent characteristics unique to each product or service category.By means of analyzing cases,either successful or undesirable,it suggests the brand name translation had better imply their underlying features.Such principles may result in amazing translations.
文摘Electrochemical water splitting is regarded as the most promising approach to produce hydrogen.However,the sluggish electrochemical reactions occurring at the anode and cathode,namely,the oxygen evolution reaction(OER)and the hydrogen evolution reaction(HER),respectively,consume a tremendous amount of energy,seriously hampering its wide application.Recently,single-atom catalysts(SACs)have been proposed to effectively enhance the kinetics of these two reactions.In this minireview,we focus on the recent progress in SACs for OER and HER applications.Three classes of SACs have been reviewed,i.e.,alloy-based SACs,carbon-based SACs and SACs supported on other compounds.Different factors affecting the activities of SACs are also highlighted,including the inherent element property,the coordination environment,the geometric structure and the loading amount of metal atoms.Finally,we summarize the current problems and directions for future development in SACs.
基金the National Natural Science Foundation of China(Nos.U22A20166,51904190,12172230,11872258 and U19A2098)the Department of Science and Technology of Guangdong Province(No.2019ZT08G315)MOE Laboratory of Deep Earth Science and Engineering(No.DESE202102).
文摘Understanding the size effect exhibited by the fracture mechanism of anisotropic geomaterials is important for engineering practice. In this study, the anisotropic features of the nominal strength, apparent fracture toughness, effective fracture energy and fracture process zone(FPZ) size of geomaterials were first analyzed by systematic size effect fracture experiments. The results showed that the nominal strength and the apparent fracture toughness decreased with increasing bedding plane inclination angle.The larger the specimen size was, the smaller the nominal strength and the larger the apparent fracture toughness was. When the bedding inclination angle increased from 0° to 90°, the effective fracture energy and the effective FPZ size both first decreased and then increased within two complex variation stages that were bounded by the 45° bedding angle. Regardless of the inherent anisotropy of geomaterials,the nominal strength and apparent fracture toughness can be predicted by the energy-based size effect law, which demonstrates that geomaterials have obvious quasi-brittle characteristics. Theoretical analysis indicated that the true fracture toughness and energy dissipation can be calculated by linear elastic fracture mechanics only when the brittleness number is higher than 10;otherwise, size effect tests should be adopted to determine the fracture parameters.
基金The National Basic Research and Development Program ("973" Program) of China under contract No2009CB421202the National Natural Science Foundation of China under contract No 40706061the National High Technol-ogy Development Program ("863" Program) of China under contract Nos 2007AA12Z137 and 2008AA09Z104
文摘The Changjiang （Yangtze） Estuary is located in the East China Sea shelf with shallow water. Affected by the tide mixing and the runoff of the Changjiang River and the Qiantang River the turbidity is very high. Generally, the water-leaving radiance is high in the turbid water because of the large particle scattering. Based on the in-situ data and ocean color remote sensing data of SeaWiFS, it was found that there was a black water region with the normalized water-leaving radiances less than 0.5 mW/（cm2-μm2-sr）. The optical principle of the occurrence of this black water was analyzed by the inherent optical properties and the ocean color components. The results show that black water is caused by the relative low values of the suspended particle matter concentration and the back scattering ratio. In the black water region, the percentage of the phytoplankton absorption was relatively high, and the large size of the phytoplankton caused the low value of the particle backscattering ratio.
基金supported by the National Natural Science Foundation of China(Grant No.51609091)the Fundamental Research Funds for the Central Universities(Grant No.2015MS102)
文摘Tendon force is an essential concept to predict welding distortion such as longitudinal shrinkage and welding induced buckling in thin plate fabrication. In this study,three approaches with experimental,theoretical and computational analysis,are examined to evaluate the magnitude of tendon force. In detail,inherent deformation theory is introduced first,the theoretical analysis to obtain the inherent strain solution is also reviewed; and then analytical solution for tendon force is achieved. Also,the theory of FE analysis for welding is introduced and implemented in a computation to obtain the transient temperature distribution,plastic strain,residual stress and welding distortion in a bead-on-plate welded joint with 2. 28 mm in thickness. The longitudinal displacement is employed to evaluate tendon force directly,and these computed inherent strain and inherent stress can also be employed to evaluate tendon force by integration approach later. All the evaluated magnitudes of tendon force have a good agreement with each other.
基金Supported by the National Natural Science Foundation of China (Nos.40706060,60802089)the National High Technology Research and Development Program of China (863 Program) (No.2007AA092102)the Dragon Project (No.5292)
文摘We tested and modified the quasi-analytical algorithm （QAA） using 57 groups of field data collected in the spring of 2003 in the Yellow Sea and East China Sea. The QAA performs well in deriving total absorption coefficients of typical coastal waters. The average percentage difference （APD） is in a range of 13.9%-38.5% for the total absorption coefficient （13.9% at 440 nm）, and differences in particle backscattering coefficient bbp（2） are less than 50% （in the case of the updated QAA）. To obtain improved results, we modified the QAA by adjusting the empirical relationships. The modified algorithm is then applied to the field data to test its performance. The APDs were 44.7%-46.6% for bbp（λ） and 9.9%-32.8% （9.9% at 555 nm） for the total absorption coefficient. This indicates that the modified QAA derives better results. We also used the modified model to derive phytoplankton pigment absorption （aph） and detritus and CDOM absorption （aug） coefficients. The APDs for aph and a dg at 440 nm are 37.1% and 19.8%. In this paper, we discuss error sources using the measured dataset. More independent field data can improve this algorithm and derive better results.
基金Supported by the National Key Research and Development Program of China(2016YFB0301701)National Natural Science Foundation of China(21606258).
文摘With a growing population, an increasing number of petrochemical facilities are built with larger capacity and more complexity, which pose a great risk to assets, community and environment. The value of inherently safer design is recognized with time by all stakeholders, and an effective tool is needed to evaluate and compare inherent safety of alternative technologies. This study developed a safety index to evaluate existing technologies for their safety levels and guide inherently safer design. The Integrated Risk-based Safety Index(IRSI) was developed based on a comprehensive review of petrochemical processes, incident cases from Sinopec and US Chemical Safety Board, and existing safety index systems. The IRSI included all major hazards, including fire, explosion,toxic release, dust explosion, physical explosion, and runaway. Also, the integrated life cycle approach considered chemical hazards, equipment failure rates and safety measures in this risk-based index. Advanced modeling techniques, PHAST simulation and Neural Network, were used in the development of three novel sub-indices in the projects, fire, explosion and toxic release. The index system could be easily incorporated into a user friendly tool for the ease of application. A case study of hydrogen dioxide was conducted using the IRSI, which showed its capability for evaluating the safety level of process facilities.
基金National Natural Science Foundation ofChina!( No. 592 752 0 3)
文摘Welding deformations can be predicted by inherent strains that are assumed to be distributed in the welds and nearby area. This method is more convenient compared with the thermo elasto plastic finite element method because only elastic analysis is necessary. The problem is how to know the inherent strains in advance during deformation analysis. The relations between inherent strains and welding parameters based on some experimental curves and a 3 D FEM model were introduced. According to this study, the longitudinal and transverse inherent strains that are the most important factors on welding deformations can be determined. The effectiveness of the proposed methods is demonstrated through the deformation analysis of a large welded cylinder with multipass welds as an example.
文摘Digraph-based causal models have been widely used to model the cause and effect behavior of process systems. Signed digraphs （SDG） capture the direction of the effect. It should be mentioned that there are loops in SDG generated from chemical process. From the point of the inherent operability, the worst unsafe factor is the SDG having positive loops that means any disturbance occurring within the loop will propagate through the nodes one by one and are amplified gradually, so the system may lose control, which may lead to an accident. So finding the positive loops in a SDG and treating these unsafe factors in a proper manner can improve the inherent safety of a chemical process. This article proposed a method that can detect the above-mentioned unsafe factors in the proc- ess conceptual design stage automatically through the analysis of the SDG generated from the chemical process. A case study is illustrated to show the working of the algorithm, and then a complicated case from industry is studied to depict the effectiveness of the proposed algorithm.
基金Project(51007006) supported by the National Natural Science Foundation of ChinaProject(20090185120023) supported by the Ph.D Programs Foundation for New Teacher of Ministry of Education of China
文摘A potential energy framework for assessment of grid vulnerability was presented.In the framework,the branch potential energy function model was constructed.Two indexes,current vulnerability and forecasting vulnerability,were calculated.The current vulnerability was used to identify the current vulnerable area through calculating the distance between the current transmitted power and initial transmitted power;and the forecast vulnerability under variation of power injection was used to predict the vulnerable area of next step and verify the current vulnerable area.Numerical simulation was performed under variant operating conditions with IEEE-30 bus system,which shows that almost area of 90% overlaps between current vulnerable area and forecasting vulnerable area,the overlapped area is termed as inherent vulnerable area of grid.When considering N-1 contingency,the assessment results of this method proposed agree with those of optimal power flow.When considering N-2 contingency,optimal power flow fails to obtain correct results,while the method based on energy framework gives reliable results.
基金Supported by National Natural Science Foundation of China(Grant No11272355)
文摘Strengthening and toughening mechanisms in composite ceramics is complex. A change in a single parameter induces multiple property variations. The multiple changes in properties are often incompletely represented in theoretical models. This incompleteness in the parameter chosen fails to explain the mechanism of failure in composite ceramics. The exponential toughness function is used to represent the pull-out toughening mechanism, which dominates the crack growth resistance curve（R-curve）. The strengthening-toughening model is established based on the Mori-Tanaka method（M-T method）. The influence of inherent defects on toughness function and strength is analyzed by using this model. The theoretical result is compared with the experiment data. This model exactly reflects the change in strength. The theoretical result indicates that defects change the toughness function. Moreover, micro-cracks increase toughness size ac, and the strength of crack instable extensions acutely decreases as defect content increases. This presented model establishes the relationship among the important mechanical parameters of defect, strength, elastic modulus, and the R-curve.
基金financial support from the National Natural Science Foundation of China(Grant No.11774044)。
文摘Layered two-dimensional(2 D)materials have received tremendous attention due to their unique physical and chemical properties when downsized to single or few layers.Several types of layered materials,especially transition metal dichalcogenides(TMDs)have been demonstrated to be good electrode materials due to their interesting physical and chemical properties.Apart from TMDs,post-transition metal chalcogenides(PTMCs)recently have emerged as a family of important semiconducting materials for electrochemical studies.PTMCs are layered materials which are composed of post-transition metals raging from main group IIIA to group VA(Ga,In,Ge,Sn,Sb and Bi)and group VI chalcogen atoms(S,selenium(Se)and tellurium(Te)).Although a large number of literatures have reviewed the electrochemical and electrocatalytic applications of TMDs,less attention has been focused on PTMCs.In this review,we focus our attention on PTMCs with the aim to provide a summary to describe their fundamental electrochemical properties and electrocatalytic activity towards hydrogen evolution reaction(HER).The characteristic chemical compositions and crystal structures of PTMCs are firstly discussed,which are different from TMDs.Then,inherent electrochemistry of PTMCs is discussed to unveil the well-defined redox behaviors of PTMCs,which could potentially affect their efficiency when applied as electrode materials.Following,we focus our attention on electrocatalytic activity of PTMCs towards HER including novel synthetic strategies developed for the optimization of their HER activity.This review ends with the perspectives for the future research direction in the field of PTMC based electrocatalysts.
文摘Fracture data of both parent metal and weldment metals from surface cracked tensile plates made of 2219-T87 Al alloy at cryogenic temperatures were correlated using a modified inherent flaw model. Fracture parameters to generate the failure assessment diagram were determined for the material. Fracture analysis was carried out considering the ultimate tensile strength value and the fracture data of aluminium base metal and weldment metal generated from center–surface cracked tensile specimens having different thicknesses. The failure assessment diagram of a material generated from tensile fracture plate configuration can be applied to failure pressure estimation of any cracked component, made of the same material.
