Poly （ m-phenylene isophthalamine） （PMIA） and Poly（ p-phenylene terphthalamine） （PPTA） are among the most important high-temperature resistant aramid fibers. The pyrolysis behaviors of these two fibers under i...Poly （ m-phenylene isophthalamine） （PMIA） and Poly（ p-phenylene terphthalamine） （PPTA） are among the most important high-temperature resistant aramid fibers. The pyrolysis behaviors of these two fibers under inert gases were studied using pyrolysis-gas chromatography/mass spectrometry （Py-GC/MS） and thermogravimetric analysis coupled with mass spectrometry （ TGA-DTA/MS ）. The pyrolysis processes of PMIA and PPTA are distinguishing, and the stepwise pyrolysates reflect these differences. A mechanism system of pyrolysis is suggested, which involving hydrolysis and homolysis, At low pyrolysis temperatures, hydrolysis is a primary reaction, and it is very noticeable in the first-step pyrolysis region of PMIA. Elevating pyrolysis temperature, homolysis is enhanced and keep a large advantage in the high temperature range. On the other hand, at higher temperatures, carbonization happens and the homolysis and carbonization of PPTA are emphasized more than of PMIA.展开更多
In order to study the morphological variations among wild Anthocidaris crassispina groups in the southeast coast of China, six groups collected from Daya Bay, Egong Bay, Hailing Island, and Nan＇ao Island in Guangzhou...In order to study the morphological variations among wild Anthocidaris crassispina groups in the southeast coast of China, six groups collected from Daya Bay, Egong Bay, Hailing Island, and Nan＇ao Island in Guangzhou Province, Weizhou Island in Guangxi Province and Ningde City in Fujian Province were analyzed in this paper. Six morphometric traits were measured and the degrees of morphological variations among wild Anthocidaris crassispina groups were compared using four multivariate analyses, one-way ANOVA analysis, variation coefficient method, cluster analysis and discriminant analysis. The results of one-way ANOVA analysis showed that there were significant differences in the six morphometric traits between Weizhou Island＇s population and the other five groups. The variation coefficient analysis showed that the difference between the Weizhou Island＇s population and Hailing Is- land＇s population reached the interspecific level. The results of cluster analysis showed that the morphometric characters of Daly Bay＇s population, Egong Bay＇s population and Nan＇ao＇s population were more similar, but the groups from Weizhou Island and Ningde City were the most divergent. The discriminant analysis showed that the identification accuracy of A. crassispina was 47.8%-86%, and the total dis- criminant accuracy was 65.3%. All the analysis results above suggest that certain morphological variation has been generated among A. crassispina groups from differ- ent origins due to geographical isolation and different environmental factors.展开更多
Asymptotic analysis is conducted for outwardly propagating spherical flames with large activation energy. The spherical flame structure consists of the preheat zone, reaction zone, and equilibrium zone. Analytical sol...Asymptotic analysis is conducted for outwardly propagating spherical flames with large activation energy. The spherical flame structure consists of the preheat zone, reaction zone, and equilibrium zone. Analytical solutions are separately obtained in these three zones and then asymp- totically matched. In the asymptotic analysis, we derive a correlation describing the spherical flame temperature and propagation speed changing with the flame radius. This cor- relation is compared with previous results derived in the limit of infinite value of activation energy. Based on this correla- tion, the properties of spherical flame propagation are inves- tigated and the effects of Lewis number on spherical flame propagation speed and extinction stretch rate are assessed. Moreover, the accuracy and performance of different mod- els used in the spherical flame method are examined. It is found that in order to get accurate laminar flame speed and Markstein length, non-linear models should be used.展开更多
There has been considerable debate about the major factors responsible for the dramatic decline of China＇s energy intensity in the 1980s and 1990s. However, few detailed analysis has been done to explain the fluctuat...There has been considerable debate about the major factors responsible for the dramatic decline of China＇s energy intensity in the 1980s and 1990s. However, few detailed analysis has been done to explain the fluctuation in energy intensity during 2002-005. In this paper, we use the structural decomposition analysis （SDA） to decompose energy intensity into five determining factors： Energy input coefficient, technology coefficient （Leontief inverse coefficient）, final demands structure by product, final demands by category and final energy consumption coefficient. We then further decompose two coefficients, energy input coefficient and technology coefficient, into structure and real coefficient. Empirical study is carried out based on the energy-input-output tables from 1987 to 2005 in 2000 constant price. The results show that between 1987 and 2002, energy input structure accounts for most of the decline in energy intensity. However, the input structure and final demands structure by product explain the increase of the energy intensity between 2002 and 2005.展开更多
Planetary gear trains are widely applied in various transmission units.Whether strengths of all gears are accurately calculated or not can affect reliability of the entire system significantly.Strength calculation met...Planetary gear trains are widely applied in various transmission units.Whether strengths of all gears are accurately calculated or not can affect reliability of the entire system significantly.Strength calculation method for planetary gear trains usually follows the method for cylindrical gears,in which the worst meshing positions for both contact stress and bending stress cannot be determined precisely,and calculation results tend to be conservative.To overcome these shortcomings,a kinematics analysis for a planetary gear train is firstly performed,in which the influence of relative speed is investigated.Then the finite element strength analysis of a planetary gear train based on its transient meshing properties is carried out in ANSYS.Time–history curves of contact and bending stresses of sun gear,planetary gears and ring gear are respectively obtained.Also the accurate moment and its corresponding position of the maximum stress are precisely determined.Finally,calculation results of finite element method(FEM)and traditional method are compared in order to verify the effectiveness.Simulation and comparison show the stability of the proposed method in this paper.Researches in this paper establish the foundations for fatigue analysis and optimization for a planetary gear train.展开更多
Discusses the symplectic integration of separable Hamiltonian ordinary and partial differential equations (PDE). Results of a von Neumann analysis; Spectra of linearized Hamiltonian PDEs.
Increasing bacteria levels in the Lower Neches River caused by Hurricane Harvey has been of a serious concern.This study is to analyze the historical water sampling measurements and real-time water quality data collec...Increasing bacteria levels in the Lower Neches River caused by Hurricane Harvey has been of a serious concern.This study is to analyze the historical water sampling measurements and real-time water quality data collected with wireless sensors to monitor and evaluate water quality under different hydrological and hydraulic conditions.The statistical and Pearson correlation analysis on historical water samples determines that alkalinity,chloride,hardness,conductivity,and pH are highly correlated,and they decrease with increasing flow rate due to dilution.The flow rate has positive correlations with Escherichia coli,total suspended solids,and turbidity,which demonstrates that runoff is one of the causes of the elevated bacteria and sediment loadings in the river.The correlation between E.coli and turbidity indicates that turbidity greater than 45 nephelometric turbidity units in the Neches River can serve as a proxy for E.coli to indicate the bacterial outbreak.A series of statistical tools and an innovative two-layer data smoothing filter are developed to detect outliers,fill missing values,and filter spikes of the sensor measurements.The correlation analysis on the sensor data illustrates that the elevated sediment/bacteria/algae in the river is either caused by the first flush rain and heavy rain events in December to March or practices of land use and land cover.Therefore,utilizing sensor measurements along with rainfall and discharge data is recommended to monitor and evaluate water quality,then in turn to provide early alerts on water resources management decisions.展开更多
In this study, the relationship between major meteorological factors and tobacco chemical components in different altitudes of Yongde County, Lincang Region of Yunnan Province was studied using correlation analysis an...In this study, the relationship between major meteorological factors and tobacco chemical components in different altitudes of Yongde County, Lincang Region of Yunnan Province was studied using correlation analysis and path analysis methods.The results showed that there was a difference on meteorological factors in different altitudes, causing different impacts on chemical components of flue-cured tobacco; contents of nicotine and total nitrogen decreased with the rising of altitude, conversely, total sugar and reducing sugar contents increased with the rising trend of altitude, and the differences on the contents of potassium （K） and chlorine（CI）, and the ratio of K to CI in different altitudes were not significant, at the altitude of 1 250-1 450 m, each chemical component indicator was better. The correlation between main meteorological factors and conventional chemical components of tobacco leaves was as follows： contents of reducing sugar and total sugar increased with the increase of rainfall and relative humidity, and decreased with the increase of sunshine duration; nicotine content increased with the increase of accumulated temperature and sunshine duration; total nitrogen （N） content increased with the increase of daily mean temperature and accumulated temperature; sugar-alkali ratio increased with the increase of rainfall. Path analysis showed that the direct effect of sunshine duration on reducing sugar and total sugar of tobacco leaves was faint, but the indirect effect was obvious; meanwhile, the direct and indirect effects of it on nicotine and total N were the greatest.展开更多
[Objective] The aim was to compare and analyze microwave coherent and incoherent scattering models in a corn field. [Method] In the research, based on a coherent scattering model （Stile）, we proposed a coherent scat...[Objective] The aim was to compare and analyze microwave coherent and incoherent scattering models in a corn field. [Method] In the research, based on a coherent scattering model （Stile）, we proposed a coherent scattering model exclusive for corn, in which, physical optics （PO） and infinite-length dielectric cylinder were used to calculate single-scattering matrices of corn leaves and stalks. In addition, coherent components produced from interaction among the scattering mechanisms were also considered and this coherent model was compared with the Michigan Mi- crowave Canopy Scattering （MIMICS） model. The measured data in a corn filed in Gongzhuling in Jilin Province were used as the input parameters of the coherent and incoherent models. We simulated backscattering coefficients of VV and HH po- larization at L and C bands and made a comparison between the simulation results. [Result] The simulation results at L-band were poor, which indicated that we could not find regularity at early growth stage of vegetation. In addition, comparisons be- tween coherent and incoherent scattering models proved that the coherence triggered by the scattering mechanism was small. [Conclusion] In the research, we analyzed differences between coherent and incoherent scattering models with change of incident angle, and further analysis on the differences with change of vegetation and soil needed to be made in future.展开更多
文摘Poly （ m-phenylene isophthalamine） （PMIA） and Poly（ p-phenylene terphthalamine） （PPTA） are among the most important high-temperature resistant aramid fibers. The pyrolysis behaviors of these two fibers under inert gases were studied using pyrolysis-gas chromatography/mass spectrometry （Py-GC/MS） and thermogravimetric analysis coupled with mass spectrometry （ TGA-DTA/MS ）. The pyrolysis processes of PMIA and PPTA are distinguishing, and the stepwise pyrolysates reflect these differences. A mechanism system of pyrolysis is suggested, which involving hydrolysis and homolysis, At low pyrolysis temperatures, hydrolysis is a primary reaction, and it is very noticeable in the first-step pyrolysis region of PMIA. Elevating pyrolysis temperature, homolysis is enhanced and keep a large advantage in the high temperature range. On the other hand, at higher temperatures, carbonization happens and the homolysis and carbonization of PPTA are emphasized more than of PMIA.
基金Supported by National Key Technology Research and Development Program(2012BAD18B02,2012BAD18B01-2)Special Scientific Research Fund of Marine Public Welfare Profession of China(201205021-3)National Nonprofit Institute Research Grant of CATAS-TCGRI(2015TS05)~~
文摘In order to study the morphological variations among wild Anthocidaris crassispina groups in the southeast coast of China, six groups collected from Daya Bay, Egong Bay, Hailing Island, and Nan＇ao Island in Guangzhou Province, Weizhou Island in Guangxi Province and Ningde City in Fujian Province were analyzed in this paper. Six morphometric traits were measured and the degrees of morphological variations among wild Anthocidaris crassispina groups were compared using four multivariate analyses, one-way ANOVA analysis, variation coefficient method, cluster analysis and discriminant analysis. The results of one-way ANOVA analysis showed that there were significant differences in the six morphometric traits between Weizhou Island＇s population and the other five groups. The variation coefficient analysis showed that the difference between the Weizhou Island＇s population and Hailing Is- land＇s population reached the interspecific level. The results of cluster analysis showed that the morphometric characters of Daly Bay＇s population, Egong Bay＇s population and Nan＇ao＇s population were more similar, but the groups from Weizhou Island and Ningde City were the most divergent. The discriminant analysis showed that the identification accuracy of A. crassispina was 47.8%-86%, and the total dis- criminant accuracy was 65.3%. All the analysis results above suggest that certain morphological variation has been generated among A. crassispina groups from differ- ent origins due to geographical isolation and different environmental factors.
基金supported by the National Natural Science Foundation of China (50976003,51136005)Doctoral Fund of Ministry of Education of China (20100001120003)
文摘Asymptotic analysis is conducted for outwardly propagating spherical flames with large activation energy. The spherical flame structure consists of the preheat zone, reaction zone, and equilibrium zone. Analytical solutions are separately obtained in these three zones and then asymp- totically matched. In the asymptotic analysis, we derive a correlation describing the spherical flame temperature and propagation speed changing with the flame radius. This cor- relation is compared with previous results derived in the limit of infinite value of activation energy. Based on this correla- tion, the properties of spherical flame propagation are inves- tigated and the effects of Lewis number on spherical flame propagation speed and extinction stretch rate are assessed. Moreover, the accuracy and performance of different mod- els used in the spherical flame method are examined. It is found that in order to get accurate laminar flame speed and Markstein length, non-linear models should be used.
基金supported by the National Natural Science Foundation of China under Grant Nos.70871108, 70810107020
文摘There has been considerable debate about the major factors responsible for the dramatic decline of China＇s energy intensity in the 1980s and 1990s. However, few detailed analysis has been done to explain the fluctuation in energy intensity during 2002-005. In this paper, we use the structural decomposition analysis （SDA） to decompose energy intensity into five determining factors： Energy input coefficient, technology coefficient （Leontief inverse coefficient）, final demands structure by product, final demands by category and final energy consumption coefficient. We then further decompose two coefficients, energy input coefficient and technology coefficient, into structure and real coefficient. Empirical study is carried out based on the energy-input-output tables from 1987 to 2005 in 2000 constant price. The results show that between 1987 and 2002, energy input structure accounts for most of the decline in energy intensity. However, the input structure and final demands structure by product explain the increase of the energy intensity between 2002 and 2005.
基金This work is supported in part by National Natural Science Fund(Grant No.51375282)Program for Changjiang Scholars and Innovative Research Team in University(Grant No.IRT1266)Special funds for Cultivation of Taishan Scholars and Postgraduate Innovation Fund of Shandong University of Science&Technology(Grant No.YC140314).
文摘Planetary gear trains are widely applied in various transmission units.Whether strengths of all gears are accurately calculated or not can affect reliability of the entire system significantly.Strength calculation method for planetary gear trains usually follows the method for cylindrical gears,in which the worst meshing positions for both contact stress and bending stress cannot be determined precisely,and calculation results tend to be conservative.To overcome these shortcomings,a kinematics analysis for a planetary gear train is firstly performed,in which the influence of relative speed is investigated.Then the finite element strength analysis of a planetary gear train based on its transient meshing properties is carried out in ANSYS.Time–history curves of contact and bending stresses of sun gear,planetary gears and ring gear are respectively obtained.Also the accurate moment and its corresponding position of the maximum stress are precisely determined.Finally,calculation results of finite element method(FEM)and traditional method are compared in order to verify the effectiveness.Simulation and comparison show the stability of the proposed method in this paper.Researches in this paper establish the foundations for fatigue analysis and optimization for a planetary gear train.
文摘Discusses the symplectic integration of separable Hamiltonian ordinary and partial differential equations (PDE). Results of a von Neumann analysis; Spectra of linearized Hamiltonian PDEs.
基金supported by Center for Resiliency(CfR)at Lamar University(Grant No.22PSSO1).
文摘Increasing bacteria levels in the Lower Neches River caused by Hurricane Harvey has been of a serious concern.This study is to analyze the historical water sampling measurements and real-time water quality data collected with wireless sensors to monitor and evaluate water quality under different hydrological and hydraulic conditions.The statistical and Pearson correlation analysis on historical water samples determines that alkalinity,chloride,hardness,conductivity,and pH are highly correlated,and they decrease with increasing flow rate due to dilution.The flow rate has positive correlations with Escherichia coli,total suspended solids,and turbidity,which demonstrates that runoff is one of the causes of the elevated bacteria and sediment loadings in the river.The correlation between E.coli and turbidity indicates that turbidity greater than 45 nephelometric turbidity units in the Neches River can serve as a proxy for E.coli to indicate the bacterial outbreak.A series of statistical tools and an innovative two-layer data smoothing filter are developed to detect outliers,fill missing values,and filter spikes of the sensor measurements.The correlation analysis on the sensor data illustrates that the elevated sediment/bacteria/algae in the river is either caused by the first flush rain and heavy rain events in December to March or practices of land use and land cover.Therefore,utilizing sensor measurements along with rainfall and discharge data is recommended to monitor and evaluate water quality,then in turn to provide early alerts on water resources management decisions.
文摘In this study, the relationship between major meteorological factors and tobacco chemical components in different altitudes of Yongde County, Lincang Region of Yunnan Province was studied using correlation analysis and path analysis methods.The results showed that there was a difference on meteorological factors in different altitudes, causing different impacts on chemical components of flue-cured tobacco; contents of nicotine and total nitrogen decreased with the rising of altitude, conversely, total sugar and reducing sugar contents increased with the rising trend of altitude, and the differences on the contents of potassium （K） and chlorine（CI）, and the ratio of K to CI in different altitudes were not significant, at the altitude of 1 250-1 450 m, each chemical component indicator was better. The correlation between main meteorological factors and conventional chemical components of tobacco leaves was as follows： contents of reducing sugar and total sugar increased with the increase of rainfall and relative humidity, and decreased with the increase of sunshine duration; nicotine content increased with the increase of accumulated temperature and sunshine duration; total nitrogen （N） content increased with the increase of daily mean temperature and accumulated temperature; sugar-alkali ratio increased with the increase of rainfall. Path analysis showed that the direct effect of sunshine duration on reducing sugar and total sugar of tobacco leaves was faint, but the indirect effect was obvious; meanwhile, the direct and indirect effects of it on nicotine and total N were the greatest.
基金Supported by Hunan Provincial Natural Science Foundation(10JJ4027)Opening Fund of State Key Laboratory of Information Engineering in Surveying,Mapping and Remote Sensing(10R01)~~
文摘[Objective] The aim was to compare and analyze microwave coherent and incoherent scattering models in a corn field. [Method] In the research, based on a coherent scattering model （Stile）, we proposed a coherent scattering model exclusive for corn, in which, physical optics （PO） and infinite-length dielectric cylinder were used to calculate single-scattering matrices of corn leaves and stalks. In addition, coherent components produced from interaction among the scattering mechanisms were also considered and this coherent model was compared with the Michigan Mi- crowave Canopy Scattering （MIMICS） model. The measured data in a corn filed in Gongzhuling in Jilin Province were used as the input parameters of the coherent and incoherent models. We simulated backscattering coefficients of VV and HH po- larization at L and C bands and made a comparison between the simulation results. [Result] The simulation results at L-band were poor, which indicated that we could not find regularity at early growth stage of vegetation. In addition, comparisons be- tween coherent and incoherent scattering models proved that the coherence triggered by the scattering mechanism was small. [Conclusion] In the research, we analyzed differences between coherent and incoherent scattering models with change of incident angle, and further analysis on the differences with change of vegetation and soil needed to be made in future.
