The high cycle fatigue response of a high V-alloyed powder metallurgy tool steel （AISI 11） with different inclusion sizes was studied. Two materials of this grade at a similar hardness of about HRC 60 were subjected...The high cycle fatigue response of a high V-alloyed powder metallurgy tool steel （AISI 11） with different inclusion sizes was studied. Two materials of this grade at a similar hardness of about HRC 60 were subjected to axial loading fatigue tests, tensile tests and fracture toughness measurements to investigate their mechanical properties. Large inclusion above 70 ~rn is indicated to be responsible for the tensile fracture which happens before yielding. The fatigue strength obtained up to 107 cycles is found to decrease from approximately 1 538 MPa to 1000 MPa with the inclusion size increasing above 30 Izm. The internally induced crack initiation is mainly attributed to the surface compressive residual stress of 300-450 MPa. Fractographic evaluation demonstrates that the crack initiation and propagation controlling factors of the two materials are almost the same, indicating that the two factors would be insignificantly affected by the inclusion size level. Paris sizes of the two materials both show a tendency to decrease as the ratio of stress intensity factor of crack origin to factor of fish-eye increases. The investigation into the relationship between stress intensity factors and fatigue life of the two materials further indicates that the high cycle fatigue behavior of AISI 11 is controlled by crack propagation.展开更多
Ethylene was tested as a sprout inhibitor on potatoes intended for processing over the 2006-2007 and the 2007-2008 storage seasons. Russet Burbank, Shepody, Innovator, FL-1867, and FL-1833 were loaded into the Univers...Ethylene was tested as a sprout inhibitor on potatoes intended for processing over the 2006-2007 and the 2007-2008 storage seasons. Russet Burbank, Shepody, Innovator, FL-1867, and FL-1833 were loaded into the University of Maine potato research facility in October of 2006. Ethylene gas was metered into the storage until a concentration of 0.1 ppm was reached and then held for one week. At weekly intervals, the ethylene concentration was increased to 0.3 ppm, 0.6 ppm, 12 ppm, 5.0 ppm and 102 ppm. Subsequently, the concentration was maintained at 10.0 ppm for the duration of the storage season. Control potatoes received chlorpropham （CIPC） for sprout control. The trial was repeated in the 2007-2008 storage season. The Agtron readings were performed on the processed potatoes at the end of the storage season. There was no difference in the US color grade between the CIPC-treated and ethylene-treated tubers within any tested variety in either storage season. Sprout inhibition of the ethylene-treated potatoes was acceptable for normal storage length of the potato varieties tested. Ethylene may have promise as an alternate to CIPC for sprout control in potato storages.展开更多
Studying about the effect of four pseudomonas and two serratia isolates on growth of Fusarium oxysporum showed that, Pseudomonasfluorescens No.2 ＆ No.3 and Serratia marcescens No.2 gave highest inhibition zones which...Studying about the effect of four pseudomonas and two serratia isolates on growth of Fusarium oxysporum showed that, Pseudomonasfluorescens No.2 ＆ No.3 and Serratia marcescens No.2 gave highest inhibition zones which were 37.33, 35,00 and 31.33 mm, respectively. Evaluating about the effect ofpseudomonas and serratia culture filtrates at three concentrations （10, 25, 50%） on the linear growth and spore germination ofFusarium oxysporum revealed that, all filtrates of the tested isolates reduced the mycelial growth and spore germination of F. oxysporum. All filtrates of the tested isolates at 50% concentration completely inhabited spore germination ofF. oxysporurn. Culture filtrates of Pseudomonasputida and Serratia marcensens No.2 at 50% concentration reduced the mycelial growth of F. oxysporurn by 80.74 and 80.37% respectively. In this respect, all tested isolates made lysis to mycelial of F. oxysporum except Pseudornonasfluorescens No.3. Effect of treating cucumber seeds with cell suspension of pseudomonas and serratia isolates on incidence of Fusarium wilt disease revealed that all isolates were effective in reducing disease incidence and disease severity and increasing the percentage of healthy plants compared to the control. Pseudornonasfluorescens No.3 and Serratia marcensens No.2 were the best isolates and completely prevented the disease incidence.展开更多
In order to clarify the differences of very high cycle fatigue(VHCF) behavior of nickel based superalloy IN718 with different loading frequencies,stress-controlled fatigue tests were carried out by using ultrasonic te...In order to clarify the differences of very high cycle fatigue(VHCF) behavior of nickel based superalloy IN718 with different loading frequencies,stress-controlled fatigue tests were carried out by using ultrasonic testing method(20 KHz) and rotary bending testing method(52.5 Hz),both at room temperatures,to establish stress versus cycles to failure(S-N) relationships.Results disclosed that cycles to failure at a given stress level increased with an increase of the applied frequency,i.e.,the higher frequency produced an upper shift of the S-N curves.Fractographic analysis suggested that crack initiation and propagation behaviors had large differences:cracks in low-frequency tests preferentially initiated from multiple sources on the specimen surface,while in high-frequency tests,cracks mostly originated from a unique source of subsurface inclusions.Subsequently,frequency-involved modeling was proposed,based on the damage accumulation theory,which could well illustrate qualitatively those comparisons due to different loading frequencies.展开更多
Prevention of annual"green tides"caused by blooms of the green macroalga Ulva prolifera,which have occurred in the Yellow Sea since 2007,has received much attention.Increasing evidence indicates that micro-p...Prevention of annual"green tides"caused by blooms of the green macroalga Ulva prolifera,which have occurred in the Yellow Sea since 2007,has received much attention.Increasing evidence indicates that micro-propagules on the rafts used for Porphyra yezoensis aquaculture along the coastline of Jiangsu Province in China,were the primary source of these green tides.In this study,we investigated the effectiveness of a silicone antifouling coating for preventing the adhesion and germination of U.prolifera micro-propagules on bamboo and nylon ropes,which have been used in rafts for P.yezoensis aquaculture.Our results demonstrated that a coating of silicone(Sylgard 184)containing 1.0 wt.%sodium benzoate(NaB)could reduce the adhesion rate to<5%and completely inhibited the growth of U.prolifera propagules on the coated surfaces.Coating bamboo and nylon ropes with NaB-incorporated silicone thus proved a potentially effective method for controlling the initial biomass accumulation of U.prolifera.展开更多
基金Project(2007BAE51B05)supported by the National Key Technologies Research and Development Program of China
文摘The high cycle fatigue response of a high V-alloyed powder metallurgy tool steel （AISI 11） with different inclusion sizes was studied. Two materials of this grade at a similar hardness of about HRC 60 were subjected to axial loading fatigue tests, tensile tests and fracture toughness measurements to investigate their mechanical properties. Large inclusion above 70 ~rn is indicated to be responsible for the tensile fracture which happens before yielding. The fatigue strength obtained up to 107 cycles is found to decrease from approximately 1 538 MPa to 1000 MPa with the inclusion size increasing above 30 Izm. The internally induced crack initiation is mainly attributed to the surface compressive residual stress of 300-450 MPa. Fractographic evaluation demonstrates that the crack initiation and propagation controlling factors of the two materials are almost the same, indicating that the two factors would be insignificantly affected by the inclusion size level. Paris sizes of the two materials both show a tendency to decrease as the ratio of stress intensity factor of crack origin to factor of fish-eye increases. The investigation into the relationship between stress intensity factors and fatigue life of the two materials further indicates that the high cycle fatigue behavior of AISI 11 is controlled by crack propagation.
文摘Ethylene was tested as a sprout inhibitor on potatoes intended for processing over the 2006-2007 and the 2007-2008 storage seasons. Russet Burbank, Shepody, Innovator, FL-1867, and FL-1833 were loaded into the University of Maine potato research facility in October of 2006. Ethylene gas was metered into the storage until a concentration of 0.1 ppm was reached and then held for one week. At weekly intervals, the ethylene concentration was increased to 0.3 ppm, 0.6 ppm, 12 ppm, 5.0 ppm and 102 ppm. Subsequently, the concentration was maintained at 10.0 ppm for the duration of the storage season. Control potatoes received chlorpropham （CIPC） for sprout control. The trial was repeated in the 2007-2008 storage season. The Agtron readings were performed on the processed potatoes at the end of the storage season. There was no difference in the US color grade between the CIPC-treated and ethylene-treated tubers within any tested variety in either storage season. Sprout inhibition of the ethylene-treated potatoes was acceptable for normal storage length of the potato varieties tested. Ethylene may have promise as an alternate to CIPC for sprout control in potato storages.
文摘Studying about the effect of four pseudomonas and two serratia isolates on growth of Fusarium oxysporum showed that, Pseudomonasfluorescens No.2 ＆ No.3 and Serratia marcescens No.2 gave highest inhibition zones which were 37.33, 35,00 and 31.33 mm, respectively. Evaluating about the effect ofpseudomonas and serratia culture filtrates at three concentrations （10, 25, 50%） on the linear growth and spore germination ofFusarium oxysporum revealed that, all filtrates of the tested isolates reduced the mycelial growth and spore germination of F. oxysporum. All filtrates of the tested isolates at 50% concentration completely inhabited spore germination ofF. oxysporurn. Culture filtrates of Pseudomonasputida and Serratia marcensens No.2 at 50% concentration reduced the mycelial growth of F. oxysporurn by 80.74 and 80.37% respectively. In this respect, all tested isolates made lysis to mycelial of F. oxysporum except Pseudornonasfluorescens No.3. Effect of treating cucumber seeds with cell suspension of pseudomonas and serratia isolates on incidence of Fusarium wilt disease revealed that all isolates were effective in reducing disease incidence and disease severity and increasing the percentage of healthy plants compared to the control. Pseudornonasfluorescens No.3 and Serratia marcensens No.2 were the best isolates and completely prevented the disease incidence.
基金supported by the National Natural Science Foundation of China (Grant Nos. 10872105 and 51071094)
文摘In order to clarify the differences of very high cycle fatigue(VHCF) behavior of nickel based superalloy IN718 with different loading frequencies,stress-controlled fatigue tests were carried out by using ultrasonic testing method(20 KHz) and rotary bending testing method(52.5 Hz),both at room temperatures,to establish stress versus cycles to failure(S-N) relationships.Results disclosed that cycles to failure at a given stress level increased with an increase of the applied frequency,i.e.,the higher frequency produced an upper shift of the S-N curves.Fractographic analysis suggested that crack initiation and propagation behaviors had large differences:cracks in low-frequency tests preferentially initiated from multiple sources on the specimen surface,while in high-frequency tests,cracks mostly originated from a unique source of subsurface inclusions.Subsequently,frequency-involved modeling was proposed,based on the damage accumulation theory,which could well illustrate qualitatively those comparisons due to different loading frequencies.
基金supported by the National Natural Science Foundation of China(Grant No.41276115)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No. XDA11020302)the National Basic Research Program of China(Grant No. 2010CB428706)
文摘Prevention of annual"green tides"caused by blooms of the green macroalga Ulva prolifera,which have occurred in the Yellow Sea since 2007,has received much attention.Increasing evidence indicates that micro-propagules on the rafts used for Porphyra yezoensis aquaculture along the coastline of Jiangsu Province in China,were the primary source of these green tides.In this study,we investigated the effectiveness of a silicone antifouling coating for preventing the adhesion and germination of U.prolifera micro-propagules on bamboo and nylon ropes,which have been used in rafts for P.yezoensis aquaculture.Our results demonstrated that a coating of silicone(Sylgard 184)containing 1.0 wt.%sodium benzoate(NaB)could reduce the adhesion rate to<5%and completely inhibited the growth of U.prolifera propagules on the coated surfaces.Coating bamboo and nylon ropes with NaB-incorporated silicone thus proved a potentially effective method for controlling the initial biomass accumulation of U.prolifera.
