Three kinds of welds were made using low frequency pulse current variable polarity tungsten inter gas （LPVPTIG） with argon shielding, direct current TIG （DCTIG） with helium shielding and high frequency pulse curr...Three kinds of welds were made using low frequency pulse current variable polarity tungsten inter gas （LPVPTIG） with argon shielding, direct current TIG （DCTIG） with helium shielding and high frequency pulse current variable polarity TIG （HPVPTIG） with argon shielding, respectively. It was found that macrosegregation bands with large amount of thick continuous eutectics and microporosities formed in the LPVPTIG weld due to the fluctuation of the pulse varied heat input. Only microsegregation existed in the DCTIG weld and HPVPTIG weld. However,the HPVPTIG weld had lower extent of Cu microsegregation since its welding speed was slower. The tensile results indicated that the mechanical properties of the weld decreased with the increase of the segregation extent of Cu and porosities, and LPVPTIG weld had lower tensile properties in the longitudinal direction than those in the transverse direction due to the macrosegregation bands.展开更多
The experimental study on the macro and micro characteristics of the spray from a pressure swirl nozzle embraces the growth of surface unstable wave,disintegration process,spray angle,breakup length and so on.The e...The experimental study on the macro and micro characteristics of the spray from a pressure swirl nozzle embraces the growth of surface unstable wave,disintegration process,spray angle,breakup length and so on.The effects of injection pressure,nozzle geometry and liquid properties on these characteristics are also discussed.The results are helpful to understand the underlying physics of the pressure swirl nozzle and serve as the basis for the practical design,usage and improvement of the nozzle.展开更多
Low frequency electromagnetic casting （LFEC） process with the application of an induction coil outside the conventional direct chill （DC） casting mould was used to prepare the flat ingot of 2524 alloy and the effe...Low frequency electromagnetic casting （LFEC） process with the application of an induction coil outside the conventional direct chill （DC） casting mould was used to prepare the flat ingot of 2524 alloy and the effect of electromagnetic field on the microstructure and macrosegregation of this alloy was systematically studied. The results show that the fiat ingot prepared by the LFEC process has a finer and more uniform as-cast microstructure and the grain morphology is transformed from dendrite and rosette-like to equiaxed structure. The LFEC process also shows a significant effect on macrosegregation, and with the application of electromagnetic field during casting process, the segregation in the centre of the ingot is obviously reduced. The mechanism of these effects was also discussed.展开更多
The effects of low frequency electromagnetic field on the macro-physical fields in the semi-continuous casting process of aluminum alloys and the microstructure and crack in the billets were studied and analyzed by th...The effects of low frequency electromagnetic field on the macro-physical fields in the semi-continuous casting process of aluminum alloys and the microstructure and crack in the billets were studied and analyzed by the numerical and experimental methods.Comparison of the results for the macro-physical fields in the low frequency electromagnetic casting（LFEC） process with the conventional DC casting process indicates the following characters due to the application of electromagnetic field：an entirely changed direction and remarkably increased velocity of melt flow;a uniform distribution and a decreased gradient of temperature;elevated isothermal lines;a reduced sump depth;decreased stress and plastic deformation.Further,the microstructure of the billets is refined remarkably and the crack in the billets is eliminated in LFEC process because of modification of the macro-physical fields induced by the application of low frequency electromagnetic field.展开更多
Nonequilibrium statistical theory of fracture is a theory of fracture that macromechanical quantities can be derived from the microscopic atomic mechanism of microcrack(or microvoid)evolution kinetcs by means of noneq...Nonequilibrium statistical theory of fracture is a theory of fracture that macromechanical quantities can be derived from the microscopic atomic mechanism of microcrack(or microvoid)evolution kinetcs by means of nonequilibrium statistical physical concepts and methods. The microcrack evolution equation is the central equation in the theory.The coefficents of the equation, the microcrack growth rate and the microcrack nucleation rate,come from microscopic atomic mechanism.The solution of the equation connects with macromechanical quantities by the model of the weakest chain. All the other formulas and quantities, for instance, distribution function,fracture probability, reliability, failure rate and macromechanical quantities such as strength, toughness, life etc. and their statistical distribution function and statistical fluctuation are derived in a unified fashion and expressed by a few physical parameters. This theory can be widely applied to various kinds of fracture, such as the brittle, fatigue, delayed and environmental fracture of metals and structural ceramics. The theoretical framework of this theory is given in this paper.展开更多
[Objective] The aim was to study characters of pollen grains of tetraploid lines and diploid control line of Chrysanthemum cinerariifolium (Trev.) Vis.,morphological characters,fertility of pollen grain and germinatio...[Objective] The aim was to study characters of pollen grains of tetraploid lines and diploid control line of Chrysanthemum cinerariifolium (Trev.) Vis.,morphological characters,fertility of pollen grain and germination percentage of seeds. [Method] Pollen grains were prepared by sulphuric acid-acetyl oxide decomposition method. The lengths of polar axis and equatorial axis of pollen grains were determined with general optical microscope. The morphology of pollen grains was observed with SEM (scanning electron microscope) and the typical visual fields of 2 500× (or 2 000×),7 000× were taken pictures. [Result] Comparing with the diploid control line,the pollen grains of five tetraploid lines which were tested were different from the diploid line in morphology,sculpture,etc.. 4 of the 5 tested samples were significant larger than the diploid line in size and one was similar to the diploid line. [Conclusion] This research provided references for breeding tetraploid improved varieties of Chrysanthemum cinerariifolium (Trev.) Vis. with good fertility and high germination percentage.展开更多
Objectives Increased lipoprotein （a） serum concentration seems to be a cardiovascular risk factor; this has not been confirmed in extracoronary atherosclerosis complications. We therefore wished to gain a deeper ins...Objectives Increased lipoprotein （a） serum concentration seems to be a cardiovascular risk factor; this has not been confirmed in extracoronary atherosclerosis complications. We therefore wished to gain a deeper insight into relationship between the plasma concentrations of lipoprotein （a） and the micro- and macro-vascular complications of type 2 diabetes mellitus and to identify possible differences in this association. Methods This is a descriptive observational cross-sectional study. Two-hundred and seventeen elderly patients with type 2 diabetes mellitus were included from the internal medicine outclinic. Anthropometric data, analytical data （insulin reserve, basal and postprandial peptide C, glycosylated hemoglobin, renal parameters, lipid profile and clinical data as hypertension, obesity, micro and macrovascular complications were collected. Results Patients were grouped according to the type 2 diabetes mellitus time of evolution. The mean plasma concentration of lipoprotein （a） was 22.2± 17.3 mg/dL （22.1± 15.9 mg/dL for males, and 22.1 ± 18.4 mg/dL for females）. Patients with hypertension, coronary heart disease, cerebrovascular accident, microalbuminuria and proteinuria presented a statistically significant increased level of lipoprotein （a）. Similarly, the patients with hyperlipoprotein （a） （≥30 mg/dL） presented significantly increased levels of urea and total cholesterol. In the multivariate regression model, the level of lipoprotein （a） is positively correlated with coronary heart disease and diabetic nephropathy （P 〈 0.01 and P 〈 0.005, respectively）. Conclusions The elevation of plasma levels of lipoprotein （a） are associ- ated with the development of coronary heart disease and diabe tic nephropathy. Therefore, we consider that the determination of lipoprotein （a） may be a prognostic marker of vascular complications in patients with type 2 diabetes mellitus.展开更多
The archaeological site of the Sanxingdui may date back as far as 5,000 years ago. The typical profiles of Palaeo-Stagnic-Anthrosols near the ancient site were selected, which aimed to identify diagnostic horizons emp...The archaeological site of the Sanxingdui may date back as far as 5,000 years ago. The typical profiles of Palaeo-Stagnic-Anthrosols near the ancient site were selected, which aimed to identify diagnostic horizons employing methodology of soil taxonomic classification and to reveal the micromorphological properties of the paleosols. Under long-term anthropogenic mellowing, the discernible differentiation between anthrostagnic epipedon and its subhorizons as well as hydragric horizon and its subhorizons occurred in Paleo-Stagnie-Anthrosols at the archaeological site of the Sanxingdui. The mieromorphological properties diversified among each specific diagnostic subhorizon, e.g., the developed microstructure in cultivated subhorizon within anthrostagnic epipedon, closely arranged particles and considerable micropores beneficial to both of water conservation and filtration in plow subhorizon within anthrostagnic epipedon, and automorphic optical-orientation clays and calcareous corrosion in hydragric horizons. The findings above of micromorphological features related with diagnostic horizons are significant for soil taxonomic classification.展开更多
The selected modifications to the construction of grinding wheels were described which facilitate an increase in the material removal rate （grinding wheels with conic chamfer and grinding wheels with microdiscontinui...The selected modifications to the construction of grinding wheels were described which facilitate an increase in the material removal rate （grinding wheels with conic chamfer and grinding wheels with microdiscontinuities on the active surface）. Using these background details, a suggested thesis was put forward regarding the need to develop a device which will allow for the shaping of the macrogeometry of the grinding wheel （cylindrical and conical surfaces） and the microdiscontinuities within the dressing operation simultaneously. The device was presented and prepared in two functional variants （horizontal and vertical mounting of the motor）, then a prototype was described. An example of the grinding wheel active surface, shaped by using this device, was also presented. The theoretical analysis and experimental verification performed determine that the error of shaping the conic chamfer angle within the range of 0-1.5°, using the developed device, is approximately ±3%.展开更多
The ground state properties of superheavy nuclei are systematically calculated by the macroscopic-microscopic (MM) model with the Nilsson potential.The calculations well produced the ground state binding energies,α-d...The ground state properties of superheavy nuclei are systematically calculated by the macroscopic-microscopic (MM) model with the Nilsson potential.The calculations well produced the ground state binding energies,α-decay energies,and half lives of superheavy nuclei.The calculated results are systematically compared with availableexperimental data.The calculated results are also compared with theoretical results from other MM models and fromrelativistic mean-field model.The calculations and comparisons show that the MM model is reliable in superheavy regionand that the MM model results are not very sensitive to the choice of microscopic single-particle potential.展开更多
文摘Three kinds of welds were made using low frequency pulse current variable polarity tungsten inter gas （LPVPTIG） with argon shielding, direct current TIG （DCTIG） with helium shielding and high frequency pulse current variable polarity TIG （HPVPTIG） with argon shielding, respectively. It was found that macrosegregation bands with large amount of thick continuous eutectics and microporosities formed in the LPVPTIG weld due to the fluctuation of the pulse varied heat input. Only microsegregation existed in the DCTIG weld and HPVPTIG weld. However,the HPVPTIG weld had lower extent of Cu microsegregation since its welding speed was slower. The tensile results indicated that the mechanical properties of the weld decreased with the increase of the segregation extent of Cu and porosities, and LPVPTIG weld had lower tensile properties in the longitudinal direction than those in the transverse direction due to the macrosegregation bands.
文摘The experimental study on the macro and micro characteristics of the spray from a pressure swirl nozzle embraces the growth of surface unstable wave,disintegration process,spray angle,breakup length and so on.The effects of injection pressure,nozzle geometry and liquid properties on these characteristics are also discussed.The results are helpful to understand the underlying physics of the pressure swirl nozzle and serve as the basis for the practical design,usage and improvement of the nozzle.
基金Projects(51104043,51374067)supported by the National Natural Science Foundation of ChinaProject(2012CB619506)supported by the National Basic Research Program of ChinaProject(N120409002)supported by the Fundamental Research Funds for the Central Universities,China
文摘Low frequency electromagnetic casting （LFEC） process with the application of an induction coil outside the conventional direct chill （DC） casting mould was used to prepare the flat ingot of 2524 alloy and the effect of electromagnetic field on the microstructure and macrosegregation of this alloy was systematically studied. The results show that the fiat ingot prepared by the LFEC process has a finer and more uniform as-cast microstructure and the grain morphology is transformed from dendrite and rosette-like to equiaxed structure. The LFEC process also shows a significant effect on macrosegregation, and with the application of electromagnetic field during casting process, the segregation in the centre of the ingot is obviously reduced. The mechanism of these effects was also discussed.
基金Project(2005CB623707)supported by National Basic Research Project of China
文摘The effects of low frequency electromagnetic field on the macro-physical fields in the semi-continuous casting process of aluminum alloys and the microstructure and crack in the billets were studied and analyzed by the numerical and experimental methods.Comparison of the results for the macro-physical fields in the low frequency electromagnetic casting（LFEC） process with the conventional DC casting process indicates the following characters due to the application of electromagnetic field：an entirely changed direction and remarkably increased velocity of melt flow;a uniform distribution and a decreased gradient of temperature;elevated isothermal lines;a reduced sump depth;decreased stress and plastic deformation.Further,the microstructure of the billets is refined remarkably and the crack in the billets is eliminated in LFEC process because of modification of the macro-physical fields induced by the application of low frequency electromagnetic field.
文摘Nonequilibrium statistical theory of fracture is a theory of fracture that macromechanical quantities can be derived from the microscopic atomic mechanism of microcrack(or microvoid)evolution kinetcs by means of nonequilibrium statistical physical concepts and methods. The microcrack evolution equation is the central equation in the theory.The coefficents of the equation, the microcrack growth rate and the microcrack nucleation rate,come from microscopic atomic mechanism.The solution of the equation connects with macromechanical quantities by the model of the weakest chain. All the other formulas and quantities, for instance, distribution function,fracture probability, reliability, failure rate and macromechanical quantities such as strength, toughness, life etc. and their statistical distribution function and statistical fluctuation are derived in a unified fashion and expressed by a few physical parameters. This theory can be widely applied to various kinds of fracture, such as the brittle, fatigue, delayed and environmental fracture of metals and structural ceramics. The theoretical framework of this theory is given in this paper.
基金Supported by the Fundamental Research Funds for the Central Universities (SWJTU09BR221)~~
文摘[Objective] The aim was to study characters of pollen grains of tetraploid lines and diploid control line of Chrysanthemum cinerariifolium (Trev.) Vis.,morphological characters,fertility of pollen grain and germination percentage of seeds. [Method] Pollen grains were prepared by sulphuric acid-acetyl oxide decomposition method. The lengths of polar axis and equatorial axis of pollen grains were determined with general optical microscope. The morphology of pollen grains was observed with SEM (scanning electron microscope) and the typical visual fields of 2 500× (or 2 000×),7 000× were taken pictures. [Result] Comparing with the diploid control line,the pollen grains of five tetraploid lines which were tested were different from the diploid line in morphology,sculpture,etc.. 4 of the 5 tested samples were significant larger than the diploid line in size and one was similar to the diploid line. [Conclusion] This research provided references for breeding tetraploid improved varieties of Chrysanthemum cinerariifolium (Trev.) Vis. with good fertility and high germination percentage.
文摘Objectives Increased lipoprotein （a） serum concentration seems to be a cardiovascular risk factor; this has not been confirmed in extracoronary atherosclerosis complications. We therefore wished to gain a deeper insight into relationship between the plasma concentrations of lipoprotein （a） and the micro- and macro-vascular complications of type 2 diabetes mellitus and to identify possible differences in this association. Methods This is a descriptive observational cross-sectional study. Two-hundred and seventeen elderly patients with type 2 diabetes mellitus were included from the internal medicine outclinic. Anthropometric data, analytical data （insulin reserve, basal and postprandial peptide C, glycosylated hemoglobin, renal parameters, lipid profile and clinical data as hypertension, obesity, micro and macrovascular complications were collected. Results Patients were grouped according to the type 2 diabetes mellitus time of evolution. The mean plasma concentration of lipoprotein （a） was 22.2± 17.3 mg/dL （22.1± 15.9 mg/dL for males, and 22.1 ± 18.4 mg/dL for females）. Patients with hypertension, coronary heart disease, cerebrovascular accident, microalbuminuria and proteinuria presented a statistically significant increased level of lipoprotein （a）. Similarly, the patients with hyperlipoprotein （a） （≥30 mg/dL） presented significantly increased levels of urea and total cholesterol. In the multivariate regression model, the level of lipoprotein （a） is positively correlated with coronary heart disease and diabetic nephropathy （P 〈 0.01 and P 〈 0.005, respectively）. Conclusions The elevation of plasma levels of lipoprotein （a） are associ- ated with the development of coronary heart disease and diabe tic nephropathy. Therefore, we consider that the determination of lipoprotein （a） may be a prognostic marker of vascular complications in patients with type 2 diabetes mellitus.
基金supported by the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No KZCX2-YW-409)
文摘The archaeological site of the Sanxingdui may date back as far as 5,000 years ago. The typical profiles of Palaeo-Stagnic-Anthrosols near the ancient site were selected, which aimed to identify diagnostic horizons employing methodology of soil taxonomic classification and to reveal the micromorphological properties of the paleosols. Under long-term anthropogenic mellowing, the discernible differentiation between anthrostagnic epipedon and its subhorizons as well as hydragric horizon and its subhorizons occurred in Paleo-Stagnie-Anthrosols at the archaeological site of the Sanxingdui. The mieromorphological properties diversified among each specific diagnostic subhorizon, e.g., the developed microstructure in cultivated subhorizon within anthrostagnic epipedon, closely arranged particles and considerable micropores beneficial to both of water conservation and filtration in plow subhorizon within anthrostagnic epipedon, and automorphic optical-orientation clays and calcareous corrosion in hydragric horizons. The findings above of micromorphological features related with diagnostic horizons are significant for soil taxonomic classification.
文摘The selected modifications to the construction of grinding wheels were described which facilitate an increase in the material removal rate （grinding wheels with conic chamfer and grinding wheels with microdiscontinuities on the active surface）. Using these background details, a suggested thesis was put forward regarding the need to develop a device which will allow for the shaping of the macrogeometry of the grinding wheel （cylindrical and conical surfaces） and the microdiscontinuities within the dressing operation simultaneously. The device was presented and prepared in two functional variants （horizontal and vertical mounting of the motor）, then a prototype was described. An example of the grinding wheel active surface, shaped by using this device, was also presented. The theoretical analysis and experimental verification performed determine that the error of shaping the conic chamfer angle within the range of 0-1.5°, using the developed device, is approximately ±3%.
基金National Natural Science Foundation of China under Grant Nos.10125521 and 10535010the State Key Basic Research and Development Program of China under Grant Nos.G2000077400 and 2007CB815004+1 种基金the CAS Knowledge Innovation Project under Grant No.KJCX2-SW-N02the Fund of the Education Ministry of China under Grant No.20010284036
文摘The ground state properties of superheavy nuclei are systematically calculated by the macroscopic-microscopic (MM) model with the Nilsson potential.The calculations well produced the ground state binding energies,α-decay energies,and half lives of superheavy nuclei.The calculated results are systematically compared with availableexperimental data.The calculated results are also compared with theoretical results from other MM models and fromrelativistic mean-field model.The calculations and comparisons show that the MM model is reliable in superheavy regionand that the MM model results are not very sensitive to the choice of microscopic single-particle potential.
