Contact fatigue issues become more and more crucial in gear industry as they significantly affect the reliability and service life of associated mechanical systems such as wind turbine gearboxes.The contact fatigue be...Contact fatigue issues become more and more crucial in gear industry as they significantly affect the reliability and service life of associated mechanical systems such as wind turbine gearboxes.The contact fatigue behavior is mostly determined by the mechanical properties of materials and stress fields near the contact area,which is further influenced by the lubrication and surface roughness due to pressure fluctuations.In this study,a numerical model incorporating the lubrication state,tooth surface roughness,residual stress,and mechanical properties of the material is developed to determine the contact fatigue behavior of a megawatt level wind turbine carburized gear.The variations of the hardness and residual stress along the depth were characterized by the Vickers hardness measurement and X-ray diffraction test,respectively.The elastohydrodynamic lubrication theory was applied to predict the contact pressure distribution,highlighting the influence of the surface roughness that stemed from the original measurement through an optical profiler.The stress histories of the studied material points during a complete contact loading cycle were fast calculated using the discreteconcrete fast Fourier transformation(DC-FFT)method.Modified Dang Van diagrams under different working conditions were determined to estimate the contact fatigue failure risk.The effect of the root mean square(RMS)value of the surface roughness on the failure risk at critical material points were discussed in detail.Results revealed that the surface roughness significantly increases the contact fatigue failure risk within a shallow area,and the maximum risk appears near the surface.展开更多
To evaluate the impact of <em>Ceratina cyanea</em> on fruit and seed yields of sunflower, experimental field was set up from June to July in 2016 and 2017 at Dang. Observations were done on 540 capitula di...To evaluate the impact of <em>Ceratina cyanea</em> on fruit and seed yields of sunflower, experimental field was set up from June to July in 2016 and 2017 at Dang. Observations were done on 540 capitula divided in four treatments: two treatments differentiated according to the presence or absence of protection on capitula regarding<em> Ceratina cyanea</em> and other flowering insects’ visits;the third with capitula protected and uncovered when florets were opened, to allow <em>C. cyanea</em> visits and flowers bagged uncovered and rebagged without the visit of insects or any other organisms. Bee’s daily rhythm of activity, its foraging behavior on florets and its pollination efficiency were evaluated. Bee’s daily rhythm of activity, its foraging behavior on flowers and its pollination efficiency were evaluated. Results show that, <em>C. cyanea</em> foraged on <em>Helianthus annuus</em> flowers throughout its whole blooming period. Among 32 insect species recorded on <em>H. annuus</em> capitula, <em>C. cyanea</em> ranked second accounting for 10.79% all visits, after <em>Apis mellifera</em> (76.06%). On florets, individual bees intensely harvested nectar and slightly collected pollen. The mean duration of a visit per floret was 3.62 sec for nectar harvest and 9.58 sec for pollen collection. For the two years, through its pollination efficiency on <em>H. annuus</em>, <em>C. cyanea</em> has increased the fruiting rate by 65.90%, the percentage of fruit with seed by 63.56% and the percentage of normal seeds by 76.11%. Based on these results, we recommend the protection of <em>C. cyanea</em> nests at the vicinity of sunflower fields to increase its fruit and seed yields in the Adamaoua Region of Cameroon.展开更多
A decline in the immunopotential of the host plays acritical factor(s) in the occurrence of infections with methicillin-resistant Staphylococcus aureus (MRSA) or microorganisms by opportunistic infection. In such an i...A decline in the immunopotential of the host plays acritical factor(s) in the occurrence of infections with methicillin-resistant Staphylococcus aureus (MRSA) or microorganisms by opportunistic infection. In such an infection, no way out for therapeutic concept, therefore bi-directional trial was the final choice. So we selected aformula, Dang Gui Liu Huang Tang (dLHT), which could both augmentimmune factorsin host and exert bacteriostatic effect. We sought to break through the epidemic by MRSA especially in elderly patient, by the fundamental and clinical trial by employing minor TCM, characterizing bidirectional ability of the decoction by western methods. Animal Experiment: Mitomycin-C (MMC)-treated mice with or without the infection of MRSA were made. The experimental design was made up to examine the bacteriostatic action as well as the immunopo-tentiating bias of the promising Chinese herbal medicine, dLHT, which was first proved for its immune potentiating activities as well as their sensitivity to antibiotics, but not direct aseptic effect was clear for MRSA. Both basic and clinical data showed that this formula was effective on repelling from the infectious focus after the treatment of MRSA infection. After the administration of dLHT, the number of white blood cells in MMC-treated mice recovered to 80% of the normal level. In addition, the phagocytic activity of macrophages increased to 70% in the dLHT-treated group, while that of the non-treated group was only 20%. The bactericidal activity also recovered to the level close to the normal value by dLHT. The ratio of neutrophils in the dLHT-administered group increased to 2.2% (normal mice, 2.6%), whereas that in the non-terated group was only 0.5%. The bacterial count in the liver of MRSA-challenged mice reached the peak at six hours after the challenge in both dLHT-treated and non-treated mice. However, the number of bacteria in dLHT group was much greater than that in the non-treated group. The bacterial count in the blood showed an increase 12 and 24 展开更多
Objective:To evaluate the therapeutic efficacy of acupuncture plus Dang Gui Bu Xue Qu Feng Tang for benign essential blepharospasm(BEB).Methods:A prospective randomized controlled trial was performed.A total of 105 pa...Objective:To evaluate the therapeutic efficacy of acupuncture plus Dang Gui Bu Xue Qu Feng Tang for benign essential blepharospasm(BEB).Methods:A prospective randomized controlled trial was performed.A total of 105 participants were randomized 1:1:1 into an acupuncture group,a herbal medicine group and an acupuncture plus herbal medicine group.Participants in the acupuncture group received manual acupuncture treatment,twice a week.Participants in the herbal medicine group received Dang Gui Bu Xue Qu Feng Tang,oral administration,once a day.Participants in the acupuncture plus herbal medicine group received both treatments.The therapeutic effects of the three groups were evaluated after four weeks of treatment.The primary outcome was the Jankovic rating scale(JRS)score,and the secondary outcome was the blepharospasm disability index(BSDI)score.Results:After four weeks of treatment,the JRS total scores significantly decreased in all three groups versus baseline(P<0.05).A greater reduction in the JRS total score was reported in participants in the acupuncture plus herbal medicine group(P<0.05),but there was no significant difference between the acupuncture group and the herbal medicine group(P>0.05).The acupuncture plus herbal medicine group had a greater decrease in the JRS severity score than the herbal medicine group(P<0.05).The reduction in the JRS frequency score was not significantly different among the three groups(P>0.05).The BSDI scores significantly decreased in all three groups versus baseline(P<0.05),but the reduction in the BSDI score was insignificantly different among the three groups(P>0.05).Conclusion:It is effective in the treatment of BEB either to use acupuncture and Dang Gui Bu Xue Qu Feng Tang alone or in combination.The combination therapy shows a more significant effect than either of the treatment alone.展开更多
The design and sizing of new mechanical components which are intended to operate under cyclic loads often require an acceptable level of confidence that the components will meet pre-defined fatigue strength objectives...The design and sizing of new mechanical components which are intended to operate under cyclic loads often require an acceptable level of confidence that the components will meet pre-defined fatigue strength objectives for crack initiation. For loads with multiple amplitudes and mean values, models based on Palmgren-Miner’s linear cumulative damage hypothesis and on multiple S/N curves (stress-no. cycles) are widely used in estimations for the duration of crack initiation. In this paper a procedure for generating S/N curves for multiple stress ratios by interpolation or extrapolation from the data available for two such curves is proposed. At any number of cycles, the stress for crack initiation is calculated from the far field macroscopic stresses of the known curves using Dang Van fatigue criterion and microscopic stresses evaluated at the grain level. An algorithm is presented for uniaxial loading and results verifications against curves established from laboratory tests with elastic and plastic stresses are shown and discussed for notched and un-notched specimens.展开更多
基金The work was supported by the National Natural Science Foundation of China(Nos.U1864210,51775060,and 51705043)Chongqing Research Program on Technology Innovation and Application Demonstration(No.cstc2018jszx-cyzdX0053).
文摘Contact fatigue issues become more and more crucial in gear industry as they significantly affect the reliability and service life of associated mechanical systems such as wind turbine gearboxes.The contact fatigue behavior is mostly determined by the mechanical properties of materials and stress fields near the contact area,which is further influenced by the lubrication and surface roughness due to pressure fluctuations.In this study,a numerical model incorporating the lubrication state,tooth surface roughness,residual stress,and mechanical properties of the material is developed to determine the contact fatigue behavior of a megawatt level wind turbine carburized gear.The variations of the hardness and residual stress along the depth were characterized by the Vickers hardness measurement and X-ray diffraction test,respectively.The elastohydrodynamic lubrication theory was applied to predict the contact pressure distribution,highlighting the influence of the surface roughness that stemed from the original measurement through an optical profiler.The stress histories of the studied material points during a complete contact loading cycle were fast calculated using the discreteconcrete fast Fourier transformation(DC-FFT)method.Modified Dang Van diagrams under different working conditions were determined to estimate the contact fatigue failure risk.The effect of the root mean square(RMS)value of the surface roughness on the failure risk at critical material points were discussed in detail.Results revealed that the surface roughness significantly increases the contact fatigue failure risk within a shallow area,and the maximum risk appears near the surface.
文摘To evaluate the impact of <em>Ceratina cyanea</em> on fruit and seed yields of sunflower, experimental field was set up from June to July in 2016 and 2017 at Dang. Observations were done on 540 capitula divided in four treatments: two treatments differentiated according to the presence or absence of protection on capitula regarding<em> Ceratina cyanea</em> and other flowering insects’ visits;the third with capitula protected and uncovered when florets were opened, to allow <em>C. cyanea</em> visits and flowers bagged uncovered and rebagged without the visit of insects or any other organisms. Bee’s daily rhythm of activity, its foraging behavior on florets and its pollination efficiency were evaluated. Bee’s daily rhythm of activity, its foraging behavior on flowers and its pollination efficiency were evaluated. Results show that, <em>C. cyanea</em> foraged on <em>Helianthus annuus</em> flowers throughout its whole blooming period. Among 32 insect species recorded on <em>H. annuus</em> capitula, <em>C. cyanea</em> ranked second accounting for 10.79% all visits, after <em>Apis mellifera</em> (76.06%). On florets, individual bees intensely harvested nectar and slightly collected pollen. The mean duration of a visit per floret was 3.62 sec for nectar harvest and 9.58 sec for pollen collection. For the two years, through its pollination efficiency on <em>H. annuus</em>, <em>C. cyanea</em> has increased the fruiting rate by 65.90%, the percentage of fruit with seed by 63.56% and the percentage of normal seeds by 76.11%. Based on these results, we recommend the protection of <em>C. cyanea</em> nests at the vicinity of sunflower fields to increase its fruit and seed yields in the Adamaoua Region of Cameroon.
文摘A decline in the immunopotential of the host plays acritical factor(s) in the occurrence of infections with methicillin-resistant Staphylococcus aureus (MRSA) or microorganisms by opportunistic infection. In such an infection, no way out for therapeutic concept, therefore bi-directional trial was the final choice. So we selected aformula, Dang Gui Liu Huang Tang (dLHT), which could both augmentimmune factorsin host and exert bacteriostatic effect. We sought to break through the epidemic by MRSA especially in elderly patient, by the fundamental and clinical trial by employing minor TCM, characterizing bidirectional ability of the decoction by western methods. Animal Experiment: Mitomycin-C (MMC)-treated mice with or without the infection of MRSA were made. The experimental design was made up to examine the bacteriostatic action as well as the immunopo-tentiating bias of the promising Chinese herbal medicine, dLHT, which was first proved for its immune potentiating activities as well as their sensitivity to antibiotics, but not direct aseptic effect was clear for MRSA. Both basic and clinical data showed that this formula was effective on repelling from the infectious focus after the treatment of MRSA infection. After the administration of dLHT, the number of white blood cells in MMC-treated mice recovered to 80% of the normal level. In addition, the phagocytic activity of macrophages increased to 70% in the dLHT-treated group, while that of the non-treated group was only 20%. The bactericidal activity also recovered to the level close to the normal value by dLHT. The ratio of neutrophils in the dLHT-administered group increased to 2.2% (normal mice, 2.6%), whereas that in the non-terated group was only 0.5%. The bacterial count in the liver of MRSA-challenged mice reached the peak at six hours after the challenge in both dLHT-treated and non-treated mice. However, the number of bacteria in dLHT group was much greater than that in the non-treated group. The bacterial count in the blood showed an increase 12 and 24
文摘Objective:To evaluate the therapeutic efficacy of acupuncture plus Dang Gui Bu Xue Qu Feng Tang for benign essential blepharospasm(BEB).Methods:A prospective randomized controlled trial was performed.A total of 105 participants were randomized 1:1:1 into an acupuncture group,a herbal medicine group and an acupuncture plus herbal medicine group.Participants in the acupuncture group received manual acupuncture treatment,twice a week.Participants in the herbal medicine group received Dang Gui Bu Xue Qu Feng Tang,oral administration,once a day.Participants in the acupuncture plus herbal medicine group received both treatments.The therapeutic effects of the three groups were evaluated after four weeks of treatment.The primary outcome was the Jankovic rating scale(JRS)score,and the secondary outcome was the blepharospasm disability index(BSDI)score.Results:After four weeks of treatment,the JRS total scores significantly decreased in all three groups versus baseline(P<0.05).A greater reduction in the JRS total score was reported in participants in the acupuncture plus herbal medicine group(P<0.05),but there was no significant difference between the acupuncture group and the herbal medicine group(P>0.05).The acupuncture plus herbal medicine group had a greater decrease in the JRS severity score than the herbal medicine group(P<0.05).The reduction in the JRS frequency score was not significantly different among the three groups(P>0.05).The BSDI scores significantly decreased in all three groups versus baseline(P<0.05),but the reduction in the BSDI score was insignificantly different among the three groups(P>0.05).Conclusion:It is effective in the treatment of BEB either to use acupuncture and Dang Gui Bu Xue Qu Feng Tang alone or in combination.The combination therapy shows a more significant effect than either of the treatment alone.
文摘The design and sizing of new mechanical components which are intended to operate under cyclic loads often require an acceptable level of confidence that the components will meet pre-defined fatigue strength objectives for crack initiation. For loads with multiple amplitudes and mean values, models based on Palmgren-Miner’s linear cumulative damage hypothesis and on multiple S/N curves (stress-no. cycles) are widely used in estimations for the duration of crack initiation. In this paper a procedure for generating S/N curves for multiple stress ratios by interpolation or extrapolation from the data available for two such curves is proposed. At any number of cycles, the stress for crack initiation is calculated from the far field macroscopic stresses of the known curves using Dang Van fatigue criterion and microscopic stresses evaluated at the grain level. An algorithm is presented for uniaxial loading and results verifications against curves established from laboratory tests with elastic and plastic stresses are shown and discussed for notched and un-notched specimens.
