The bipartite graph structure exists in the connections of many objects in the real world, and the evolving modeling is a good method to describe and understand the generation and evolution within various real complex...The bipartite graph structure exists in the connections of many objects in the real world, and the evolving modeling is a good method to describe and understand the generation and evolution within various real complex networks. Previous bipartite models were proposed to mostly explain the principle of attachments, and ignored the diverse growth speed of nodes of sets in different bipartite networks. In this paper, we propose an evolving bipartite network model with adjustable node scale and hybrid attachment mechanisms, which uses different probability parameters to control the scale of two disjoint sets of nodes and the preference strength of hybrid attachment respectively. The results show that the degree distribution of single set in the proposed model follows a shifted power-law distribution when parameter r and s are not equal to 0, or exponential distribution when r or s is equal to 0. Furthermore, we extend the previous model to a semi-bipartite network model, which embeds more user association information into the internal network, so that the model is capable of carrying and revealing more deep information of each user in the network. The simulation results of two models are in good agreement with the empirical data, which verifies that the models have a good performance on real networks from the perspective of degree distribution. We believe these two models are valuable for an explanation of the origin and growth of bipartite systems that truly exist.展开更多
Peroxyacyl nitrates(PANs) are important secondary pollutants in ground-level atmosphere.Accurate prediction of atmospheric pollutant concentrations is crucial to guide effective precautions for before and during speci...Peroxyacyl nitrates(PANs) are important secondary pollutants in ground-level atmosphere.Accurate prediction of atmospheric pollutant concentrations is crucial to guide effective precautions for before and during specific pollution events. In this study, four models based on the back-propagation(BP) artificial neural network(ANN) and multiple linear regression(MLR) methods were used to predict the hourly average PAN concentrations at Peking University, Beijing, in 2014. The model inputs were atmospheric pollutant data and meteorological parameters. Model 3 using a BP-ANN based on the original variables achieved the best prediction results among the four models, with a correlation coefficient(R) of 0.7089, mean bias error of -0.0043 ppb, mean absolute error of 0.4836?ppb, root mean squared error of 0.5320?ppb, and Willmott's index of agreement of 0.8214. Based on a comparison of the performance indices of the MLR and BP-ANN models, we concluded that the BP-ANN model was able to capture the highly non-linear relationships between PAN concentration and the conventional atmospheric pollutant and meteorological parameters,providing more accurate results than the traditional MLR models did, with a markedly higher goodness of R. The selected meteorological and atmospheric pollutant parameters described a sufficient amount of PAN variation, and thus provided satisfactory prediction results. More specifically, the BP-ANN model performed very well for capturing the variation pattern when PAN concentrations were low. The findings of this study address some of the existing knowledge gaps in this research field and provide a theoretical basis for future regional air pollution control.展开更多
Two novel weakly basic anion exchange resins（SZ-1 and SZ-2） were prepared via the reaction of macroporous chloromethylated polystyrene-divinylbenzene（Cl-PS-DVB） beads with dicyclohexylamine and piperidine, respect...Two novel weakly basic anion exchange resins（SZ-1 and SZ-2） were prepared via the reaction of macroporous chloromethylated polystyrene-divinylbenzene（Cl-PS-DVB） beads with dicyclohexylamine and piperidine, respectively. The physicochemical structures of the resulting resins were characterized using Fourier Transform Infrared Spectroscopy and pore size distribution analysis. The adsorption behavior of SZ-1 and SZ-2 for benzenesulfonic acid（BA） was evaluated, and the common commercial weakly basic anion exchanger D301 was also employed for comparison purpose. Adsorption isotherms and influence of solution p H, temperature and coexisting competitive inorganic salts（Na2SO4and Na Cl） on adsorption behavior were investigated and the optimum desorption agent was obtained.Adsorption isotherms of BA were found to be well represented by the Langmuir model.Thermodynamic parameters involving ΔH, ΔG and ΔS were also calculated and the results indicate that adsorption is an exothermic and spontaneous process. Enhanced selectivity of BA sorption over sulfate on the two novel resins was observed by comparison with the commercial anion exchanger D301. The fact that the tested resins loaded with BA can be efficiently regenerated by Na Cl solution indicates the reversible sorption process. From a mechanistic viewpoint, this observation clearly suggests that electrostatic interaction is the predominant adsorption mechanism. Furthermore, results of column tests show that SZ-1possesses a better adsorption property than D301, which reinforces the feasibility of SZ-1for potential industrial application.展开更多
Composite Li metal anodes based on three-dimensional(3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density.However,uneven Li deposition be...Composite Li metal anodes based on three-dimensional(3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density.However,uneven Li deposition behavior still occurs at the top of 3D frameworks owing to the local accumulation of Li ions.To promote uniform Li deposition without top dendrite growth,herein,a layered multifunctional framework based on oxidation-treated polyacrylonitrile(OPAN) and metal-organic framework(MOF) derivatives was proposed for rationally regulating the distribution of Li ions flux,nucleation sites,and electrical conductivity.Profiting from these merits,the OPAN/carbon nano fiber-MOF(CMOF) composite framework demonstrated a reversible Li plating/stripping behavior for 500 cycles with a stable Coulombic efficiency of around 99.0% at the current density of 2 mA/cm~2.Besides,such a Li composite anode exhibited a superior cycle lifespan of over 1300 h under a low polarized voltage of 18 mV in symmetrical cells.When the Li composite anode was paired with LiFePO_(4)(LFP) cathode,the obtained full cell exhibited a stable cycling over 500 cycles.Moreover,the COMSOL Multiphysics simulation was conducted to reveal the effects on homogeneous Li ions distribution derived from the above-mentioned OPAN/CMOF framework and electrical insulation/conduction design.These electrochemical and simulated results shed light on the difficulties of designing stable and safe Li metal anode via optimizing the 3D frameworks.展开更多
In September 2018,we proposed the cutting-edge concept of“Beyond Limits Manufacturing”(BLM).BLM technology is based on the three-dimensional inner engraving or precise outer engraving of ultra-fast laser,to invent m...In September 2018,we proposed the cutting-edge concept of“Beyond Limits Manufacturing”(BLM).BLM technology is based on the three-dimensional inner engraving or precise outer engraving of ultra-fast laser,to invent micro/nano scale flow chips or devices,which makes it possible for the microform,integration,economy,safety,high efficiency,green and intelligence of research,development and manufacturing process,so as to realize transformational manufacturing in the era of Industry 4.0.In this paper,we reviewed the representative results we made in the field of micro/nano flow chemistry during the implementation of the BLM major project(December 2019 to August 2023),and discussed its application prospects in micro/nano flow chemistry.展开更多
Achieving the decoupling of ion transport and mechanical relaxation,also known as superionic conduction,is a crucial goal for electrolyte materials in energy and electronics technologies.However,constructing highly ef...Achieving the decoupling of ion transport and mechanical relaxation,also known as superionic conduction,is a crucial goal for electrolyte materials in energy and electronics technologies.However,constructing highly efficient ionic conductive pathways to overcome the trade-off that restrained segments reduce ionic conduction in polymer electrolytes still remains challenging.Given the non-covalent binding nature of supramolecular polymers,which offers advantages such as dynamic segments and easy integration of ionophilic units,here we present the creation of supramolecular polymer proton conductors(SPPCs)based on deep eutectic solvents(DESs)and polyoxometalate(POM)nanoclusters as hybrid monomers.By innovatively incorporating glycosyl and zwitterionic groups into DES precursor,the resulting glycosyl zwitterionic DESs can be non-covalently crosslinked by POM nanoclusters through synergistic hydrogen bonding and electrostatic interactions,leading to the solidification of DESs.The dense supramolecular networks formed within SPPCs serve as mechanical support and proton-conducting pathways.This gives SPPCs significant adhesive strength,high viscosity,excellent proton conductivity,and high mechanical-conductive decoupling ability.Furthermore,vanadium-substituted POM nanoclusters in SPPCs exhibit an additional pseudocapacitance for flexible supercapacitors,achieving an impressive increase in specific capacitance compared to tungsten-containing POM nanoclusters.This work highlights the immense potential of using functional supramolecular polymers to boost the development of innovative electrolyte materials.展开更多
Fischer-Tropsch(F-T)synthesis is an important route to achieve the clean fuel production.The perfor-mance of gas-liquid separation equipment involving in the progressive condensation and separation of light and heavy ...Fischer-Tropsch(F-T)synthesis is an important route to achieve the clean fuel production.The perfor-mance of gas-liquid separation equipment involving in the progressive condensation and separation of light and heavy hydrocarbons in the oil-gas products has become a bottleneck restricting the smooth operation of the F-T process.In order to remove the bottleneck,a gas-liquid vortex separator with simple structure,low pressure drop and big separation capacity was designed to achieve the efficient separation between gas and droplets for a long period.The RSM(Reynolds Stress Model)and DPM(Discrete Phase Method)are employed to simulate the flow characteristics and liquid distribution in the separator.The results show that the separation efficiency is influenced by the flow field and liquid phase concentration in the annular zone.The transverse vortex at the top of spiral arm entrains the droplets with small diam-eter into the upper annular zone.The entrained droplets rotate upward at an angle of about 37.4°.The screw pitch between neighbor liquid threads is about 0.3 m.There is a top liquid ring in the top of annular zone,where the higher is the liquid phase concentration,the lower is the separation efficiency.It is found that by changing the operating condition and the annular zone height the vortex can be strengthened but not enlarged by the inlet velocity.The screw pitch is not affected by both inlet velocity and annular zone height.The liquid phase concentration in the top liquid ring decreases with both the increases of inlet velocity and annular zone height.The total pressure drop is almost not affected by the annular zone height but is obviously affected by the inlet velocity.When the height of annular zone is more than 940 mm,the separation efficiency is not changed.Therefore,the annular zone height of 940 mm is thought to be the most economical design.展开更多
Objective:The purpose of this study was to evaluate the pregnancy outcomes among papillary thyroid cancer survivors.Methods:65 cases singleton gravidas of papillary thyroid cancer survivors treated in the Department o...Objective:The purpose of this study was to evaluate the pregnancy outcomes among papillary thyroid cancer survivors.Methods:65 cases singleton gravidas of papillary thyroid cancer survivors treated in the Department of Obstetrics,Peking University People's Hospital between January 2011 and January 2020 were selected retrospectively as the study group,and 130 cases of singleton pregnancy during the same time were randomly selected as the control group.The differences in general conditions,maternal and fetal complications between the two groups were analyzed.Risk factors of maternal complications and fetal malformation in patients with papillary thyroid cancer survivors were analyzed.Data was analyzed with t-test,χ^(2)test and logistic regression for statistical differences.Results:Totally 65 cases of papillary thyroid cancer with 70 pregnancies were analyzed,which including 65 cases achieved live birth,5 cases underwent induced labor because of fetal malformation.The study group showed higher incidence in gestational diabetes(20%vs 10%),cesarean section(39.1%vs 24.6%),postpartum hemorrhage(350193 ml vs 290181 ml)and fetal malformation(5.7%vs 1.5%),and lower live birth rate(91.4%vs 99.2%)(P<0.05).Multivariate analysis by logistic regression found that the patient's age,thyroid function,operation mode and postoperative I-131 treatment were not the risk factors which may affect the pregnancy outcomes or fetal malformation.Conclusion:Elevated maternal and fetal complications were observed among pregnancies in papillary thyroid cancer survivors.Management of these survivors may require a careful gestation monitoring,and further investigation is needed.展开更多
文摘The bipartite graph structure exists in the connections of many objects in the real world, and the evolving modeling is a good method to describe and understand the generation and evolution within various real complex networks. Previous bipartite models were proposed to mostly explain the principle of attachments, and ignored the diverse growth speed of nodes of sets in different bipartite networks. In this paper, we propose an evolving bipartite network model with adjustable node scale and hybrid attachment mechanisms, which uses different probability parameters to control the scale of two disjoint sets of nodes and the preference strength of hybrid attachment respectively. The results show that the degree distribution of single set in the proposed model follows a shifted power-law distribution when parameter r and s are not equal to 0, or exponential distribution when r or s is equal to 0. Furthermore, we extend the previous model to a semi-bipartite network model, which embeds more user association information into the internal network, so that the model is capable of carrying and revealing more deep information of each user in the network. The simulation results of two models are in good agreement with the empirical data, which verifies that the models have a good performance on real networks from the perspective of degree distribution. We believe these two models are valuable for an explanation of the origin and growth of bipartite systems that truly exist.
基金supported by the "State Key R&D Program" of China.(Nos.2017YFC0212400,2016YFC0202200)
文摘Peroxyacyl nitrates(PANs) are important secondary pollutants in ground-level atmosphere.Accurate prediction of atmospheric pollutant concentrations is crucial to guide effective precautions for before and during specific pollution events. In this study, four models based on the back-propagation(BP) artificial neural network(ANN) and multiple linear regression(MLR) methods were used to predict the hourly average PAN concentrations at Peking University, Beijing, in 2014. The model inputs were atmospheric pollutant data and meteorological parameters. Model 3 using a BP-ANN based on the original variables achieved the best prediction results among the four models, with a correlation coefficient(R) of 0.7089, mean bias error of -0.0043 ppb, mean absolute error of 0.4836?ppb, root mean squared error of 0.5320?ppb, and Willmott's index of agreement of 0.8214. Based on a comparison of the performance indices of the MLR and BP-ANN models, we concluded that the BP-ANN model was able to capture the highly non-linear relationships between PAN concentration and the conventional atmospheric pollutant and meteorological parameters,providing more accurate results than the traditional MLR models did, with a markedly higher goodness of R. The selected meteorological and atmospheric pollutant parameters described a sufficient amount of PAN variation, and thus provided satisfactory prediction results. More specifically, the BP-ANN model performed very well for capturing the variation pattern when PAN concentrations were low. The findings of this study address some of the existing knowledge gaps in this research field and provide a theoretical basis for future regional air pollution control.
基金supported by the National Natural Science Foundation of China(No.51578131)the Natural Science Foundation of Jiangsu Province,China(No.BK20131287)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘Two novel weakly basic anion exchange resins（SZ-1 and SZ-2） were prepared via the reaction of macroporous chloromethylated polystyrene-divinylbenzene（Cl-PS-DVB） beads with dicyclohexylamine and piperidine, respectively. The physicochemical structures of the resulting resins were characterized using Fourier Transform Infrared Spectroscopy and pore size distribution analysis. The adsorption behavior of SZ-1 and SZ-2 for benzenesulfonic acid（BA） was evaluated, and the common commercial weakly basic anion exchanger D301 was also employed for comparison purpose. Adsorption isotherms and influence of solution p H, temperature and coexisting competitive inorganic salts（Na2SO4and Na Cl） on adsorption behavior were investigated and the optimum desorption agent was obtained.Adsorption isotherms of BA were found to be well represented by the Langmuir model.Thermodynamic parameters involving ΔH, ΔG and ΔS were also calculated and the results indicate that adsorption is an exothermic and spontaneous process. Enhanced selectivity of BA sorption over sulfate on the two novel resins was observed by comparison with the commercial anion exchanger D301. The fact that the tested resins loaded with BA can be efficiently regenerated by Na Cl solution indicates the reversible sorption process. From a mechanistic viewpoint, this observation clearly suggests that electrostatic interaction is the predominant adsorption mechanism. Furthermore, results of column tests show that SZ-1possesses a better adsorption property than D301, which reinforces the feasibility of SZ-1for potential industrial application.
基金supported by the National Natural Science Foundation of China (52302292, 52302058, 52302085)the China Postdoctoral Science Foundation (2021M702225)+1 种基金the Anhui Province University Natural Science Research Project (2023AH030093, 2023AH040301)the Startup Research Fund of Chaohu University (KYQD-2023005, KYQD-2023051)。
文摘Composite Li metal anodes based on three-dimensional(3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density.However,uneven Li deposition behavior still occurs at the top of 3D frameworks owing to the local accumulation of Li ions.To promote uniform Li deposition without top dendrite growth,herein,a layered multifunctional framework based on oxidation-treated polyacrylonitrile(OPAN) and metal-organic framework(MOF) derivatives was proposed for rationally regulating the distribution of Li ions flux,nucleation sites,and electrical conductivity.Profiting from these merits,the OPAN/carbon nano fiber-MOF(CMOF) composite framework demonstrated a reversible Li plating/stripping behavior for 500 cycles with a stable Coulombic efficiency of around 99.0% at the current density of 2 mA/cm~2.Besides,such a Li composite anode exhibited a superior cycle lifespan of over 1300 h under a low polarized voltage of 18 mV in symmetrical cells.When the Li composite anode was paired with LiFePO_(4)(LFP) cathode,the obtained full cell exhibited a stable cycling over 500 cycles.Moreover,the COMSOL Multiphysics simulation was conducted to reveal the effects on homogeneous Li ions distribution derived from the above-mentioned OPAN/CMOF framework and electrical insulation/conduction design.These electrochemical and simulated results shed light on the difficulties of designing stable and safe Li metal anode via optimizing the 3D frameworks.
文摘In September 2018,we proposed the cutting-edge concept of“Beyond Limits Manufacturing”(BLM).BLM technology is based on the three-dimensional inner engraving or precise outer engraving of ultra-fast laser,to invent micro/nano scale flow chips or devices,which makes it possible for the microform,integration,economy,safety,high efficiency,green and intelligence of research,development and manufacturing process,so as to realize transformational manufacturing in the era of Industry 4.0.In this paper,we reviewed the representative results we made in the field of micro/nano flow chemistry during the implementation of the BLM major project(December 2019 to August 2023),and discussed its application prospects in micro/nano flow chemistry.
基金supported by the National Natural Science Foundation of China(92261110,22075097)the Education Department of Jilin Province(JJKH20241248CY).
文摘Achieving the decoupling of ion transport and mechanical relaxation,also known as superionic conduction,is a crucial goal for electrolyte materials in energy and electronics technologies.However,constructing highly efficient ionic conductive pathways to overcome the trade-off that restrained segments reduce ionic conduction in polymer electrolytes still remains challenging.Given the non-covalent binding nature of supramolecular polymers,which offers advantages such as dynamic segments and easy integration of ionophilic units,here we present the creation of supramolecular polymer proton conductors(SPPCs)based on deep eutectic solvents(DESs)and polyoxometalate(POM)nanoclusters as hybrid monomers.By innovatively incorporating glycosyl and zwitterionic groups into DES precursor,the resulting glycosyl zwitterionic DESs can be non-covalently crosslinked by POM nanoclusters through synergistic hydrogen bonding and electrostatic interactions,leading to the solidification of DESs.The dense supramolecular networks formed within SPPCs serve as mechanical support and proton-conducting pathways.This gives SPPCs significant adhesive strength,high viscosity,excellent proton conductivity,and high mechanical-conductive decoupling ability.Furthermore,vanadium-substituted POM nanoclusters in SPPCs exhibit an additional pseudocapacitance for flexible supercapacitors,achieving an impressive increase in specific capacitance compared to tungsten-containing POM nanoclusters.This work highlights the immense potential of using functional supramolecular polymers to boost the development of innovative electrolyte materials.
基金supports from the National Natural Science Foundation of China(grant nos.21706280,U1862202,91834303,21961132026).
文摘Fischer-Tropsch(F-T)synthesis is an important route to achieve the clean fuel production.The perfor-mance of gas-liquid separation equipment involving in the progressive condensation and separation of light and heavy hydrocarbons in the oil-gas products has become a bottleneck restricting the smooth operation of the F-T process.In order to remove the bottleneck,a gas-liquid vortex separator with simple structure,low pressure drop and big separation capacity was designed to achieve the efficient separation between gas and droplets for a long period.The RSM(Reynolds Stress Model)and DPM(Discrete Phase Method)are employed to simulate the flow characteristics and liquid distribution in the separator.The results show that the separation efficiency is influenced by the flow field and liquid phase concentration in the annular zone.The transverse vortex at the top of spiral arm entrains the droplets with small diam-eter into the upper annular zone.The entrained droplets rotate upward at an angle of about 37.4°.The screw pitch between neighbor liquid threads is about 0.3 m.There is a top liquid ring in the top of annular zone,where the higher is the liquid phase concentration,the lower is the separation efficiency.It is found that by changing the operating condition and the annular zone height the vortex can be strengthened but not enlarged by the inlet velocity.The screw pitch is not affected by both inlet velocity and annular zone height.The liquid phase concentration in the top liquid ring decreases with both the increases of inlet velocity and annular zone height.The total pressure drop is almost not affected by the annular zone height but is obviously affected by the inlet velocity.When the height of annular zone is more than 940 mm,the separation efficiency is not changed.Therefore,the annular zone height of 940 mm is thought to be the most economical design.
基金Research and Development Fund of Peking University People's Hospital(RDY-2020-26).
文摘Objective:The purpose of this study was to evaluate the pregnancy outcomes among papillary thyroid cancer survivors.Methods:65 cases singleton gravidas of papillary thyroid cancer survivors treated in the Department of Obstetrics,Peking University People's Hospital between January 2011 and January 2020 were selected retrospectively as the study group,and 130 cases of singleton pregnancy during the same time were randomly selected as the control group.The differences in general conditions,maternal and fetal complications between the two groups were analyzed.Risk factors of maternal complications and fetal malformation in patients with papillary thyroid cancer survivors were analyzed.Data was analyzed with t-test,χ^(2)test and logistic regression for statistical differences.Results:Totally 65 cases of papillary thyroid cancer with 70 pregnancies were analyzed,which including 65 cases achieved live birth,5 cases underwent induced labor because of fetal malformation.The study group showed higher incidence in gestational diabetes(20%vs 10%),cesarean section(39.1%vs 24.6%),postpartum hemorrhage(350193 ml vs 290181 ml)and fetal malformation(5.7%vs 1.5%),and lower live birth rate(91.4%vs 99.2%)(P<0.05).Multivariate analysis by logistic regression found that the patient's age,thyroid function,operation mode and postoperative I-131 treatment were not the risk factors which may affect the pregnancy outcomes or fetal malformation.Conclusion:Elevated maternal and fetal complications were observed among pregnancies in papillary thyroid cancer survivors.Management of these survivors may require a careful gestation monitoring,and further investigation is needed.
