TiAl alloys were produced by investment casting method combined with induction skull melting （ISM） technique. In situ scanning electron microscopy （SEM） was utilized to study the fracture characteristics and crack...TiAl alloys were produced by investment casting method combined with induction skull melting （ISM） technique. In situ scanning electron microscopy （SEM） was utilized to study the fracture characteristics and crack propagation of a notched investment cast TiAl specimens in tension under incremental loading conditions. The whole process of crack initiation, propagation and failure during tensile deformation was observed and characterized. The results show that the fracture mechanism was sensitive to not only the microcracks near the notched area but also lamellar orientation to loading axis. The high tensile stress leads to the new microcracks nucleate along lamellar interfaces of grains with favorable orientation when local stress intensity reaches the toughness threshold of the material. Thus, both plasticity and high tensile stress are required to cause notched TiAl failure.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
The effects of surface energy on phase change of water vapor at initial stage of frost growth were studied to find an effective method of restraining frost growth.The mechanism of restraining frost growth by low energ...The effects of surface energy on phase change of water vapor at initial stage of frost growth were studied to find an effective method of restraining frost growth.The mechanism of restraining frost growth by low energy surface(bigger contact angle) was analyzed based on crystal growth theory.Then,the phase change of water vapor and the process of frost growth on the copper and wax energy surfaces were observed using microscope.The results indicate that it is difficult for wax surface(low energy surface),on which there are still water droplets at 100 s,to form critical embryo,so frost growth can be restrained in a way.Water formation,droplet growth,ice formation and dendritic ice growth processes happen on both surfaces,ordinally.But the ice beads,with larger average diameter and sparse distribution on the wax surface,form later(at about 300 s) than that on the copper surface,and the dendritic ice also appears later.All of these support that ice crystal formation and dendritic crystal growth at initial stage of frost growth can be retarded on the low energy surface.展开更多
This paper is concerned with the aerodynamic functions of fly wings. The free and tethered flight analyses were performed by using a digital high-speed video camera system. A liquid droplet impacting with a wing surfa...This paper is concerned with the aerodynamic functions of fly wings. The free and tethered flight analyses were performed by using a digital high-speed video camera system. A liquid droplet impacting with a wing surface of fly was conducted to examine the wing characteristics. Microscopic observation of fly＇s wings were also conducted by using a laser beam microscope. The results of a series of observation and measurement revealed the flight characteristics of flies, such as the wing tip velocity, wing path, wing flexibility, wing structure, resistance to rain drops, and so forth.展开更多
Methods to measure consistent individual differences in behavior （i.e. animal personality） fall into two categories, subjective ratings and behavioral codings. Ratings are seldom used despite being potentially more ...Methods to measure consistent individual differences in behavior （i.e. animal personality） fall into two categories, subjective ratings and behavioral codings. Ratings are seldom used despite being potentially more efficient than codings. One potential limitation for the use of ratings is that it is assumed that long-term observers or experts in the field are required to score individuals. This can be problematic in many cases, especially for long-term ecological studies where there is high turnover in personnel. We tested whether raters who were unacquainted with subjects could produce reliable and valid personality assessments of yellow-bellied marmots Marmota flaviventris. Two raters, previously unacquainted with individuals and marmot be- havior, scored 130 subjects on fifteen different adjectives in both open-field （OF） and mirror image stimulation （MIS） trials. Eight OF and nine MIS adjectives were reliable as indicated by both a high degree of intra-observer and inter-observer reliability. Additionally, some ratings were externally valid, correlating with behavioral codings. Our data suggest that activity/exploration and sociability can be a reliable and valid measurement of personality traits in studies where raters were unacquainted with subjects. These traits are observable with the personality tests we used; otherwise researchers using unacquainted raters should be cautious in the tests they employ [Current Zoology 60 （2）： 162-169, 2014].展开更多
基金Project(51001040)supported by the National Natural Science Foundation of ChinaProject(200802130014)supported by Specialized Research Fund for the Doctoral Program of Higher Education,China+1 种基金Project(HIT.NSRIF.2010116)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(HITQNJS 2009022)supported by Development Program for Outstanding Young Teachers in Harbin Institute of Technology
文摘TiAl alloys were produced by investment casting method combined with induction skull melting （ISM） technique. In situ scanning electron microscopy （SEM） was utilized to study the fracture characteristics and crack propagation of a notched investment cast TiAl specimens in tension under incremental loading conditions. The whole process of crack initiation, propagation and failure during tensile deformation was observed and characterized. The results show that the fracture mechanism was sensitive to not only the microcracks near the notched area but also lamellar orientation to loading axis. The high tensile stress leads to the new microcracks nucleate along lamellar interfaces of grains with favorable orientation when local stress intensity reaches the toughness threshold of the material. Thus, both plasticity and high tensile stress are required to cause notched TiAl failure.
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.
基金Project(50376052) supported by the National Natural Science Foundation of ChinaProject(307013) supported by the Key Project of Chinese Ministry of EducationProject(2008BAJ12B02) supported by the National Science and Technology Pillar Program in the 11th Five-Year Plan Period
文摘The effects of surface energy on phase change of water vapor at initial stage of frost growth were studied to find an effective method of restraining frost growth.The mechanism of restraining frost growth by low energy surface(bigger contact angle) was analyzed based on crystal growth theory.Then,the phase change of water vapor and the process of frost growth on the copper and wax energy surfaces were observed using microscope.The results indicate that it is difficult for wax surface(low energy surface),on which there are still water droplets at 100 s,to form critical embryo,so frost growth can be restrained in a way.Water formation,droplet growth,ice formation and dendritic ice growth processes happen on both surfaces,ordinally.But the ice beads,with larger average diameter and sparse distribution on the wax surface,form later(at about 300 s) than that on the copper surface,and the dendritic ice also appears later.All of these support that ice crystal formation and dendritic crystal growth at initial stage of frost growth can be retarded on the low energy surface.
文摘This paper is concerned with the aerodynamic functions of fly wings. The free and tethered flight analyses were performed by using a digital high-speed video camera system. A liquid droplet impacting with a wing surface of fly was conducted to examine the wing characteristics. Microscopic observation of fly＇s wings were also conducted by using a laser beam microscope. The results of a series of observation and measurement revealed the flight characteristics of flies, such as the wing tip velocity, wing path, wing flexibility, wing structure, resistance to rain drops, and so forth.
文摘Methods to measure consistent individual differences in behavior （i.e. animal personality） fall into two categories, subjective ratings and behavioral codings. Ratings are seldom used despite being potentially more efficient than codings. One potential limitation for the use of ratings is that it is assumed that long-term observers or experts in the field are required to score individuals. This can be problematic in many cases, especially for long-term ecological studies where there is high turnover in personnel. We tested whether raters who were unacquainted with subjects could produce reliable and valid personality assessments of yellow-bellied marmots Marmota flaviventris. Two raters, previously unacquainted with individuals and marmot be- havior, scored 130 subjects on fifteen different adjectives in both open-field （OF） and mirror image stimulation （MIS） trials. Eight OF and nine MIS adjectives were reliable as indicated by both a high degree of intra-observer and inter-observer reliability. Additionally, some ratings were externally valid, correlating with behavioral codings. Our data suggest that activity/exploration and sociability can be a reliable and valid measurement of personality traits in studies where raters were unacquainted with subjects. These traits are observable with the personality tests we used; otherwise researchers using unacquainted raters should be cautious in the tests they employ [Current Zoology 60 （2）： 162-169, 2014].
