[Objectives]To study the inhibitory activity of two flavonoid glycosides isolated from Chlorophytum comosum Laxum R.Br on human nasopharyngeal carcinoma(NPC)cell line 5-8F in vitro and its mechanism.[Methods]The flavo...[Objectives]To study the inhibitory activity of two flavonoid glycosides isolated from Chlorophytum comosum Laxum R.Br on human nasopharyngeal carcinoma(NPC)cell line 5-8F in vitro and its mechanism.[Methods]The flavonoid glycosides were isolated and purified from the ethanol alcoholic extract of the roots of Liliaceae plant Chlorophytum comosum by silica gel column chromatography,macroporous resin column chromatography,Sephadex LH-20,and reverse column chromatography(ODS).The inhibitory activity of flavonoid glycosides on human nasopharyngeal carcinoma cells was analyzed by CCK-8 method,and the potential mechanism was preliminarily analyzed by molecular docking.[Results]Two flavonoid glycosides were identified as isovitexin 2″-0-rhamnoside and 7-2″-di-O-β-glucopyranosylisovitexin.Two flavonoid glycosides showed promising inhibitory effect on human nasopharyngeal carcinoma cell line 5-8F,with IC_(50) values of 24.8 and 27.5μmol/L,respectively.Molecular docking results showed that the potential targets of two flavonoid glycosides include CyclinD1,Bcl-2β-Catenin,ILK,TGF-β,in addition,two glycosides showed higher predicted binding affinity towards CyclinD1,which verifies the cytotoxicity of the two compounds on human nasopharyngeal carcinoma cell line 5-8F in vitro.[Conclusions]Two flavonoid glycosides are the active molecules in Chlorophytum comosum that can inhibit the proliferation of human nasopharyngeal carcinoma cells,and have the potential to be used in the research and development of anti nasopharyngeal carcinoma drugs.展开更多
The activation of CO on iron-based materials is a key elementary reaction for many chemical processes.We investigate CO adsorption and dissociation on a series of Fe,Fe_(3)C,Fe_(5)C_(2),and Fe_(2)C catalysts through d...The activation of CO on iron-based materials is a key elementary reaction for many chemical processes.We investigate CO adsorption and dissociation on a series of Fe,Fe_(3)C,Fe_(5)C_(2),and Fe_(2)C catalysts through density functional theory calculations.We detect dramatically different performances for CO adsorption and activation on diverse surfaces and sites.The activation of CO is dependent on the local coordination of the molecule to the surface and on the bulk phase of the underlying catalyst.The bulk properties and the different local bonding environments lead to varying interactions between the adsorbed CO and the surface and thus yielding different activation levels of the C-O bond.We also examine the prediction of CO adsorption on different types of Fe-based catalysts by machine learning through linear regression models.We combine the features originating from surfaces and bulk phases to enhance the prediction of the activation energies and perform eight different linear regressions utilizing the feature engineering of polynomial representations.Among them,a ridge linear regression model with2nd-degree polynomial feature generation predicted the best CO activation energy with a mean absolute error of 0.269 eV.展开更多
With their widespread utilization, cut-to-length harvesters have become a major source of ‘‘big data’’ for forest management as they constantly capture, and provide a daily flow of, information on log production a...With their widespread utilization, cut-to-length harvesters have become a major source of ‘‘big data’’ for forest management as they constantly capture, and provide a daily flow of, information on log production and assortment over large operational areas. Harvester data afford the calculation of the total log length between the stump and the last cut but not the total height of trees. They also contain the length and end diameters of individual logs but not always the diameter at breast height overbark(DBHOB) of harvested stems largely because of time lapse, operating and processing issues and other system deficiencies. Even when DBHOB is extracted from harvester data, errors and/or bias of the machine measurements due to the variation in the stump height of harvested stems from that specified for the harvester head prior to harvesting and diameter measurement errors may need to be corrected. This study developed(1) a system of equations for estimating DBHOB of trees from diameter overbark(DOB) measured by a harvester head at any height up to 3 m above ground level and(2) an equation to predict the total height of harvested stems in P. radiata plantations from harvester data. To generate the data required for this purpose, cut-to-length simulations of more than 3000 trees with detailed taper measurements were carried out in the computer using the cutting patterns extracted from the harvester data and stump height survey data from clearfall operations. The equation predicted total tree height from DBHOB, total log length and the small end diameter of the top log. Prediction accuracy for total tree height was evaluated both globally over the entire data space and locally within partitioned subspaces through benchmarking statistics. These statistics were better than that of the conventional height-diameter equations for P. radiata found in the literature, even when they incorporated stand age and the average height and diameter of dominant trees in the stand as predictors. So this equation when used with harvester data would outperform the conventional equations in tree height prediction. Tree and stand reconstructions of the harvested forest is the necessary first step to provide the essential link of harvester data to conventional inventory, remote sensing imagery and Li DAR data. The equations developed in this study will provide such a linkage for the most effective combined use of harvester data in predicting the attributes of individual trees, stands and forests, and product recovery for the management and planning of P. radiata plantations in New South Wales, Australia.展开更多
Ceramic cores are widely used in investment casting,and ideal properties of cores are essential for high-quality castings.Under the circumstances requiring thick cores,solid cores are likely to encounter deformation a...Ceramic cores are widely used in investment casting,and ideal properties of cores are essential for high-quality castings.Under the circumstances requiring thick cores,solid cores are likely to encounter deformation and cracking defects due to the accumulation of shrinkage.Therefore,with the superiority of ceramic stereolithography in producing complex ceramic parts,hollow cores with lattice structures were designed and fabricated.The dimensional accuracy and properties of the green and sintered bodies were evaluated.Results show the dimensional accuracy of sintered cores is controlled within±0.25 mm benefited from the precise green bodies.The mechanical properties are not obviously deteriorated.The bending strength reaches 11.94 MPa at room temperature and 12.87 MPa at 1,500℃ with a creep deformation of 0.345 mm.Furthermore,casting verifications prove that the hollow cores meet the requirements of investment casting.Smooth casting surfaces are obtained,at the same time,the core-removal efficiency is improved by over 3 times.展开更多
Two different order reduction methods of the deterministic and stochastic systems are discussed in this paper.First,the transient proper orthogonal decomposition(T-POD)method is introduced based on the high-dimensiona...Two different order reduction methods of the deterministic and stochastic systems are discussed in this paper.First,the transient proper orthogonal decomposition(T-POD)method is introduced based on the high-dimensional nonlinear dynamic system.The optimal order reduction conditions of the T-POD method are provided by analyzing the rotor-bearing system with pedestal looseness fault at both ends.The efficiency of the T-POD method is verified via comparing with the results of the original system.Second,the polynomial dimensional decomposition(PDD)method is applied to the 2 DOFs spring system considering the uncertain stiffness to study the amplitude-frequency response.The numerical results obtained by the PDD method agree well with the Monte Carlo simulation(MCS)method.The results of the PDD method can approximate to MCS better with the increasing of the polynomial order.Meanwhile,the Uniform-Legendre polynomials can eliminate perturbation of the PDD method to a certain extent via comparing it with the Gaussian-Hermite polynomials.展开更多
The transient proper orthogonal decomposition(TPOD) method is used to study dynamic behaviors of the reduced rotor-bearing models,and the fault-free model is compared with the models with looseness fault.A 22 degree o...The transient proper orthogonal decomposition(TPOD) method is used to study dynamic behaviors of the reduced rotor-bearing models,and the fault-free model is compared with the models with looseness fault.A 22 degree of freedoms(DOFs) rotor model supported by bearings is established.Both one end and two ends pedestal looseness of the liquid-film bearings are studied by analyzing the time history and the frequency-spectrum curves.The effects of the initial displacement and velocity values to frequency components of the original systems and the dimension reduction efficiency are discussed.Moreover,the effects of variation of initial conditions on the efficiency of the TPOD method are studied.Reduced models can provide guidance significance from the perspectives of the theory and numerical simplification to discuss the characteristics of pedestal looseness fault.展开更多
A method for seeking main bifurcation parameters of a class of nonlinear dynamical systems is proposed. The method is based on the effects of parametric varia- tion of dynamical systems on eigenvalues of the Frechet m...A method for seeking main bifurcation parameters of a class of nonlinear dynamical systems is proposed. The method is based on the effects of parametric varia- tion of dynamical systems on eigenvalues of the Frechet matrix. The singularity theory is used to study the engineering unfolding (EU) and the universal unfolding (UU) of an arch structure model, respectively. Unfolding parameters of EU are combination of concerned physical parameters in actual engineering, and equivalence of unfolding parameters and physical parameters is verified. Transient sets and bifurcation behaviors of EU and UU are compared to illustrate that EU can reflect main bifurcation characteristics of non- linear systems in engineering. The results improve the understanding and the scope of applicability of EU in actual engineering systems when UU is difficult to be obtained.展开更多
This paper deals with the co-existence of mixed aleatory and epistemic uncertainties in a wind turbine geared system for more reliable and robust vibration analyses.To this end,the regression-based polynomial chaos ex...This paper deals with the co-existence of mixed aleatory and epistemic uncertainties in a wind turbine geared system for more reliable and robust vibration analyses.To this end,the regression-based polynomial chaos expansion(PCE)is used to track aleatory uncertainties,and the polynomial surrogate approach(PSA)is developed to treat the epistemic uncertainties.This non-intrusive dual-layer framework shares the same collocation pool,which is extracted from the Legendre series.Moreover,the regression technique has been implemented in both layers to enhance calculation efficiency.Numerical validation is carried out to show the effectiveness of the proposed method.New vibration behaviors of the geared transmission system are observed,and the mechanism behind is discussed in detail.The findings of this paper will contribute to the insightful understanding of such wind turbine geared systems under hybrid uncertainties and are beneficial for the condition monitoring.展开更多
Since the founding of the People’s Republic of China in 1949,China’s per capita education level has risen from less than two years to 9.91 years.However,as the province with the lowest per capita education level in ...Since the founding of the People’s Republic of China in 1949,China’s per capita education level has risen from less than two years to 9.91 years.However,as the province with the lowest per capita education level in China,Tibet has only reached the level of 6.75 years per capita.This illustrates the worrying educational inequality that still exists between China’s poorer and more developed regions.This educational inequality can also be expressed by the Gini coefficient of education.In order to eliminate this educational inequality,the Chinese government has made great efforts.The Chinese government has expanded the demand for education through the right incentive system and the nine-year compulsory education law.On the other hand,the Chinese government directly or indirectly grants subsidies to education suppliers and demanders to achieve the purpose of increasing education output.Based on the positive externality of education itself,the Chinese government attaches great importance to the cultivation of human resources for offspring,and hopes to transform China’s quantity-based demographic dividend into quality-based demographic dividend,and finally realize sustained economic growth.We believe that some education-related policies promulgated by China have indeed reduced educational inequality in poor areas to some extent,but there is still potential for progress in further addressing educational inequality in poor areas by the Chinese government.展开更多
In this paper,the nonlinear parametric vibration of fluid-conveying pipes flexibly restrained at both ends and subjected to the pulsation flow excitation is investigated.The nonlinear equation of motion is derived usi...In this paper,the nonlinear parametric vibration of fluid-conveying pipes flexibly restrained at both ends and subjected to the pulsation flow excitation is investigated.The nonlinear equation of motion is derived using Hamilton^principle by considering the Kevin-Voigt viscoelastic damping,the geometric nonlinearity and the translational and rotational springs supported at the ends.The mode functions and eigen-frequencies are determined by the assumed mode method according to the elastic boundary conditions.The Galerkin method is implemented to obtain the natural frequencies and mode shapes of the pipe conveying fluid with different flow velocities.The effects of flexibly restrained conditions on stability of the pipe are analyzed.The nonlinear responses of the pipe under pulsating flow excitation are solved by the direct numerical method.The vibration behaviors are discussed in details,such as time history,frequency spectrum,phase-plane portrait,Poincare map and motion trajectory.The results show that the responses of sub-harmonic resonance and combination resonance can also be reflected in the rigidly supported pipes.The 1/5,1/8 and 1/13 sub-harmonic resonances can occur at certain excitation frequencies of the nonlinear parametric vibration system.The steady-state response amplitudes increase by a large margin and significantly affect the stability of the pipe.The effects of different spring stiffness coefficients on the parametric resonance responses are presented.For larger translational springs and rotational stiffness coefficients,the resonance frequencies shift to higher regions and the resonance amplitudes may reduce by a certain extent in accordance with the rigid-body motion.This study can provide helpful guidance on the analysis and design of piping systems subject to vibrations.展开更多
We have synthesized a series of compounds based on a piperidyl benzimidazole carboxamide structure,and tested their PARP-1 inhibitory activity,as well as cellular inhibitory activity.Some of them show great potency as...We have synthesized a series of compounds based on a piperidyl benzimidazole carboxamide structure,and tested their PARP-1 inhibitory activity,as well as cellular inhibitory activity.Some of them show great potency as PARP-1 inhibitors and antitumor activity,which are valuable for further research.In addition,the predicted ADME properties and proposed binding mode with PARP-1 of the compounds were obtained via computational simulation.展开更多
This paper presents an approach to achieve broadband absorption and temperature resistance using ceramic sub-strates.A specially formulated slurry suitable for additive manufacturing technology was developed to fabric...This paper presents an approach to achieve broadband absorption and temperature resistance using ceramic sub-strates.A specially formulated slurry suitable for additive manufacturing technology was developed to fabricate ceramic substrates with lattice structures.The lattice structure not only reduces the weight of the absorber but also facilitates the broadening of the absorption bandwidth.The experimental results demonstrate that the pro-posed structure exhibits absorption rates exceeding 88%within the frequency range of 19.9-30.41 GHz,with a relative absorption bandwidth of 41.8%under normal incidence.Furthermore,the absorber’s performance was assessed under high temperatures of up to 200℃,revealing absorption spectra that closely match the initially measured spectrum.Additive-manufactured ceramic lattice structures present a promising avenue for designing multifunctional broadband microwave absorbers capable of withstanding elevated temperatures.展开更多
Flavor characteristics of raw shrimp,high-salt and low-salt shrimp paste were evaluated and compared by sensory analysis,headspace-gas chromatography-ion mobility spectrometry(HS-GC-IMS)and solid-phase microextraction...Flavor characteristics of raw shrimp,high-salt and low-salt shrimp paste were evaluated and compared by sensory analysis,headspace-gas chromatography-ion mobility spectrometry(HS-GC-IMS)and solid-phase microextraction-gas chromatography-mass spectrometry(SPME-GC-MS).In addition,aroma profiles and aroma-active compounds in these three samples were analyzed by solvent-assisted flavor evaporation-gas chromatography-olfactometry-mass spectrometry(SAFE-GC-O-MS).Results of sensory evaluation revealed that these three samples showed significant differences in sensitivity to the W2W,W2S,W1S and W1W sensors of the electronic nose(p<0.05),which represent organic sulfides,alkane aromatic compounds,short chain alkanes,and sulfides,respectively.Assessment of sensory parameters indicated tha high-salt shrimp paste had a strong roasted and meaty aroma,while low-salt shrimp paste showed an umami aroma more similar to raw shrimp.A total of 118 volatile compounds were identified using the three afore-mentioned gas chromatography methods.Among them,37 aroma-active compounds were detected by GC-O.High-salt shrimp was shown to contain more acids,aldehydes and heterocyclic compounds,which resembled cheese,roasted and meaty aromas.In contrast,low-salt shrimp paste contained more esters,which was similar to the umami aroma profile of raw shrimp.Interestingly,pyrazines were only produced in fermented shrimp paste samples,suggesting that they were produced during the fermentation process and they may contribute unique roasted and meaty aromas,which were important for the overall aroma characteristics of shrimp paste.展开更多
基金Supported by Youth Fund Project of Zhaoqing University(QZ202235)Zhaoqing Science and Technology Plan Project(2022040311011).
文摘[Objectives]To study the inhibitory activity of two flavonoid glycosides isolated from Chlorophytum comosum Laxum R.Br on human nasopharyngeal carcinoma(NPC)cell line 5-8F in vitro and its mechanism.[Methods]The flavonoid glycosides were isolated and purified from the ethanol alcoholic extract of the roots of Liliaceae plant Chlorophytum comosum by silica gel column chromatography,macroporous resin column chromatography,Sephadex LH-20,and reverse column chromatography(ODS).The inhibitory activity of flavonoid glycosides on human nasopharyngeal carcinoma cells was analyzed by CCK-8 method,and the potential mechanism was preliminarily analyzed by molecular docking.[Results]Two flavonoid glycosides were identified as isovitexin 2″-0-rhamnoside and 7-2″-di-O-β-glucopyranosylisovitexin.Two flavonoid glycosides showed promising inhibitory effect on human nasopharyngeal carcinoma cell line 5-8F,with IC_(50) values of 24.8 and 27.5μmol/L,respectively.Molecular docking results showed that the potential targets of two flavonoid glycosides include CyclinD1,Bcl-2β-Catenin,ILK,TGF-β,in addition,two glycosides showed higher predicted binding affinity towards CyclinD1,which verifies the cytotoxicity of the two compounds on human nasopharyngeal carcinoma cell line 5-8F in vitro.[Conclusions]Two flavonoid glycosides are the active molecules in Chlorophytum comosum that can inhibit the proliferation of human nasopharyngeal carcinoma cells,and have the potential to be used in the research and development of anti nasopharyngeal carcinoma drugs.
基金financially supported from the National Natural Science Foundation of China (No.22002008)Ningxia Key Research and Development Project,China (Nos.2022BEE03002 and 2022BSB03056)funding support from Synfuels China,Co.,Ltd.and Beijing Advanced Innovation Center for Materials Genome Engineering。
文摘The activation of CO on iron-based materials is a key elementary reaction for many chemical processes.We investigate CO adsorption and dissociation on a series of Fe,Fe_(3)C,Fe_(5)C_(2),and Fe_(2)C catalysts through density functional theory calculations.We detect dramatically different performances for CO adsorption and activation on diverse surfaces and sites.The activation of CO is dependent on the local coordination of the molecule to the surface and on the bulk phase of the underlying catalyst.The bulk properties and the different local bonding environments lead to varying interactions between the adsorbed CO and the surface and thus yielding different activation levels of the C-O bond.We also examine the prediction of CO adsorption on different types of Fe-based catalysts by machine learning through linear regression models.We combine the features originating from surfaces and bulk phases to enhance the prediction of the activation energies and perform eight different linear regressions utilizing the feature engineering of polynomial representations.Among them,a ridge linear regression model with2nd-degree polynomial feature generation predicted the best CO activation energy with a mean absolute error of 0.269 eV.
基金supported by the Forestry Corporation of New South Wales
文摘With their widespread utilization, cut-to-length harvesters have become a major source of ‘‘big data’’ for forest management as they constantly capture, and provide a daily flow of, information on log production and assortment over large operational areas. Harvester data afford the calculation of the total log length between the stump and the last cut but not the total height of trees. They also contain the length and end diameters of individual logs but not always the diameter at breast height overbark(DBHOB) of harvested stems largely because of time lapse, operating and processing issues and other system deficiencies. Even when DBHOB is extracted from harvester data, errors and/or bias of the machine measurements due to the variation in the stump height of harvested stems from that specified for the harvester head prior to harvesting and diameter measurement errors may need to be corrected. This study developed(1) a system of equations for estimating DBHOB of trees from diameter overbark(DOB) measured by a harvester head at any height up to 3 m above ground level and(2) an equation to predict the total height of harvested stems in P. radiata plantations from harvester data. To generate the data required for this purpose, cut-to-length simulations of more than 3000 trees with detailed taper measurements were carried out in the computer using the cutting patterns extracted from the harvester data and stump height survey data from clearfall operations. The equation predicted total tree height from DBHOB, total log length and the small end diameter of the top log. Prediction accuracy for total tree height was evaluated both globally over the entire data space and locally within partitioned subspaces through benchmarking statistics. These statistics were better than that of the conventional height-diameter equations for P. radiata found in the literature, even when they incorporated stand age and the average height and diameter of dominant trees in the stand as predictors. So this equation when used with harvester data would outperform the conventional equations in tree height prediction. Tree and stand reconstructions of the harvested forest is the necessary first step to provide the essential link of harvester data to conventional inventory, remote sensing imagery and Li DAR data. The equations developed in this study will provide such a linkage for the most effective combined use of harvester data in predicting the attributes of individual trees, stands and forests, and product recovery for the management and planning of P. radiata plantations in New South Wales, Australia.
基金supported by the National Natural Science Foundation of China (Grant No. 52175333)Tribology Science Fund of the State Key Laboratory of Tribology,Tsinghua University (Grant No. SKLT2021B05)+1 种基金Foshan Science and Technology Innovation Team Project (Grant No. 2018IT100142)National Science and Technology Major Project of China (Grant No. J2019-VII-0002-0142)
文摘Ceramic cores are widely used in investment casting,and ideal properties of cores are essential for high-quality castings.Under the circumstances requiring thick cores,solid cores are likely to encounter deformation and cracking defects due to the accumulation of shrinkage.Therefore,with the superiority of ceramic stereolithography in producing complex ceramic parts,hollow cores with lattice structures were designed and fabricated.The dimensional accuracy and properties of the green and sintered bodies were evaluated.Results show the dimensional accuracy of sintered cores is controlled within±0.25 mm benefited from the precise green bodies.The mechanical properties are not obviously deteriorated.The bending strength reaches 11.94 MPa at room temperature and 12.87 MPa at 1,500℃ with a creep deformation of 0.345 mm.Furthermore,casting verifications prove that the hollow cores meet the requirements of investment casting.Smooth casting surfaces are obtained,at the same time,the core-removal efficiency is improved by over 3 times.
基金funding for this study from the National Natural Science Foundation of China(Grant No.11802235)the National Basic Research Program(973 Program)of China(Grant No.2015CB057400)the Basic Scientific Research Operating Expenses of Central Universities(Grant No.G2018KY0305).
文摘Two different order reduction methods of the deterministic and stochastic systems are discussed in this paper.First,the transient proper orthogonal decomposition(T-POD)method is introduced based on the high-dimensional nonlinear dynamic system.The optimal order reduction conditions of the T-POD method are provided by analyzing the rotor-bearing system with pedestal looseness fault at both ends.The efficiency of the T-POD method is verified via comparing with the results of the original system.Second,the polynomial dimensional decomposition(PDD)method is applied to the 2 DOFs spring system considering the uncertain stiffness to study the amplitude-frequency response.The numerical results obtained by the PDD method agree well with the Monte Carlo simulation(MCS)method.The results of the PDD method can approximate to MCS better with the increasing of the polynomial order.Meanwhile,the Uniform-Legendre polynomials can eliminate perturbation of the PDD method to a certain extent via comparing it with the Gaussian-Hermite polynomials.
基金Sponsored by the National Basic Research Program of China(Grant No.2015CB057400)
文摘The transient proper orthogonal decomposition(TPOD) method is used to study dynamic behaviors of the reduced rotor-bearing models,and the fault-free model is compared with the models with looseness fault.A 22 degree of freedoms(DOFs) rotor model supported by bearings is established.Both one end and two ends pedestal looseness of the liquid-film bearings are studied by analyzing the time history and the frequency-spectrum curves.The effects of the initial displacement and velocity values to frequency components of the original systems and the dimension reduction efficiency are discussed.Moreover,the effects of variation of initial conditions on the efficiency of the TPOD method are studied.Reduced models can provide guidance significance from the perspectives of the theory and numerical simplification to discuss the characteristics of pedestal looseness fault.
基金supported by the National Basic Research Program of China(973 Program)(No.2015CB057400)the National Natural Science Foundation of China(No.11602070)the China Postdoctoral Science Foundation(No.2016M590277)
文摘A method for seeking main bifurcation parameters of a class of nonlinear dynamical systems is proposed. The method is based on the effects of parametric varia- tion of dynamical systems on eigenvalues of the Frechet matrix. The singularity theory is used to study the engineering unfolding (EU) and the universal unfolding (UU) of an arch structure model, respectively. Unfolding parameters of EU are combination of concerned physical parameters in actual engineering, and equivalence of unfolding parameters and physical parameters is verified. Transient sets and bifurcation behaviors of EU and UU are compared to illustrate that EU can reflect main bifurcation characteristics of non- linear systems in engineering. The results improve the understanding and the scope of applicability of EU in actual engineering systems when UU is difficult to be obtained.
基金Project supported by the National Natural Science Foundation of China(Nos.12072263 and 11972295)the Fundamental Research Funds for the Central Universities(No.G2021KY0601)。
文摘This paper deals with the co-existence of mixed aleatory and epistemic uncertainties in a wind turbine geared system for more reliable and robust vibration analyses.To this end,the regression-based polynomial chaos expansion(PCE)is used to track aleatory uncertainties,and the polynomial surrogate approach(PSA)is developed to treat the epistemic uncertainties.This non-intrusive dual-layer framework shares the same collocation pool,which is extracted from the Legendre series.Moreover,the regression technique has been implemented in both layers to enhance calculation efficiency.Numerical validation is carried out to show the effectiveness of the proposed method.New vibration behaviors of the geared transmission system are observed,and the mechanism behind is discussed in detail.The findings of this paper will contribute to the insightful understanding of such wind turbine geared systems under hybrid uncertainties and are beneficial for the condition monitoring.
文摘Since the founding of the People’s Republic of China in 1949,China’s per capita education level has risen from less than two years to 9.91 years.However,as the province with the lowest per capita education level in China,Tibet has only reached the level of 6.75 years per capita.This illustrates the worrying educational inequality that still exists between China’s poorer and more developed regions.This educational inequality can also be expressed by the Gini coefficient of education.In order to eliminate this educational inequality,the Chinese government has made great efforts.The Chinese government has expanded the demand for education through the right incentive system and the nine-year compulsory education law.On the other hand,the Chinese government directly or indirectly grants subsidies to education suppliers and demanders to achieve the purpose of increasing education output.Based on the positive externality of education itself,the Chinese government attaches great importance to the cultivation of human resources for offspring,and hopes to transform China’s quantity-based demographic dividend into quality-based demographic dividend,and finally realize sustained economic growth.We believe that some education-related policies promulgated by China have indeed reduced educational inequality in poor areas to some extent,but there is still potential for progress in further addressing educational inequality in poor areas by the Chinese government.
基金the National Natural Science Foundation of China(Grant No.51305350,Grant No.11802235)National Key Basic Research Program of China(Grant No.613268)Aeronautics Power Foundation Program of China(Grant No.6141B090320).
文摘In this paper,the nonlinear parametric vibration of fluid-conveying pipes flexibly restrained at both ends and subjected to the pulsation flow excitation is investigated.The nonlinear equation of motion is derived using Hamilton^principle by considering the Kevin-Voigt viscoelastic damping,the geometric nonlinearity and the translational and rotational springs supported at the ends.The mode functions and eigen-frequencies are determined by the assumed mode method according to the elastic boundary conditions.The Galerkin method is implemented to obtain the natural frequencies and mode shapes of the pipe conveying fluid with different flow velocities.The effects of flexibly restrained conditions on stability of the pipe are analyzed.The nonlinear responses of the pipe under pulsating flow excitation are solved by the direct numerical method.The vibration behaviors are discussed in details,such as time history,frequency spectrum,phase-plane portrait,Poincare map and motion trajectory.The results show that the responses of sub-harmonic resonance and combination resonance can also be reflected in the rigidly supported pipes.The 1/5,1/8 and 1/13 sub-harmonic resonances can occur at certain excitation frequencies of the nonlinear parametric vibration system.The steady-state response amplitudes increase by a large margin and significantly affect the stability of the pipe.The effects of different spring stiffness coefficients on the parametric resonance responses are presented.For larger translational springs and rotational stiffness coefficients,the resonance frequencies shift to higher regions and the resonance amplitudes may reduce by a certain extent in accordance with the rigid-body motion.This study can provide helpful guidance on the analysis and design of piping systems subject to vibrations.
基金Shenzhen Sci.& Tech.Bureau (Nos.JCYJ20170816170342439 and JCYJ20170413113448742) for the financial supports
文摘We have synthesized a series of compounds based on a piperidyl benzimidazole carboxamide structure,and tested their PARP-1 inhibitory activity,as well as cellular inhibitory activity.Some of them show great potency as PARP-1 inhibitors and antitumor activity,which are valuable for further research.In addition,the predicted ADME properties and proposed binding mode with PARP-1 of the compounds were obtained via computational simulation.
基金supported by National Natural Science Foundation of China(Grant Nos.12102444,52005494).
文摘This paper presents an approach to achieve broadband absorption and temperature resistance using ceramic sub-strates.A specially formulated slurry suitable for additive manufacturing technology was developed to fabricate ceramic substrates with lattice structures.The lattice structure not only reduces the weight of the absorber but also facilitates the broadening of the absorption bandwidth.The experimental results demonstrate that the pro-posed structure exhibits absorption rates exceeding 88%within the frequency range of 19.9-30.41 GHz,with a relative absorption bandwidth of 41.8%under normal incidence.Furthermore,the absorber’s performance was assessed under high temperatures of up to 200℃,revealing absorption spectra that closely match the initially measured spectrum.Additive-manufactured ceramic lattice structures present a promising avenue for designing multifunctional broadband microwave absorbers capable of withstanding elevated temperatures.
基金supported by the National Natural Science Foundation of China[grant numbers 32072348,31671825].
文摘Flavor characteristics of raw shrimp,high-salt and low-salt shrimp paste were evaluated and compared by sensory analysis,headspace-gas chromatography-ion mobility spectrometry(HS-GC-IMS)and solid-phase microextraction-gas chromatography-mass spectrometry(SPME-GC-MS).In addition,aroma profiles and aroma-active compounds in these three samples were analyzed by solvent-assisted flavor evaporation-gas chromatography-olfactometry-mass spectrometry(SAFE-GC-O-MS).Results of sensory evaluation revealed that these three samples showed significant differences in sensitivity to the W2W,W2S,W1S and W1W sensors of the electronic nose(p<0.05),which represent organic sulfides,alkane aromatic compounds,short chain alkanes,and sulfides,respectively.Assessment of sensory parameters indicated tha high-salt shrimp paste had a strong roasted and meaty aroma,while low-salt shrimp paste showed an umami aroma more similar to raw shrimp.A total of 118 volatile compounds were identified using the three afore-mentioned gas chromatography methods.Among them,37 aroma-active compounds were detected by GC-O.High-salt shrimp was shown to contain more acids,aldehydes and heterocyclic compounds,which resembled cheese,roasted and meaty aromas.In contrast,low-salt shrimp paste contained more esters,which was similar to the umami aroma profile of raw shrimp.Interestingly,pyrazines were only produced in fermented shrimp paste samples,suggesting that they were produced during the fermentation process and they may contribute unique roasted and meaty aromas,which were important for the overall aroma characteristics of shrimp paste.