AIMTo determine the effect of suction duration on thickness and diameter of corneal flap created by microkeratome in porcine eyes in laser in situ keratomileusis (LASIK).
The rare earth (RE) elements (Ce, La) were added to binary Ti 47% Al alloys (atomic fraction) by Induction Skull Melting. The element Ce of 1.0 atomic percent was added individually, and La of 0.2 atomic percent was ...The rare earth (RE) elements (Ce, La) were added to binary Ti 47% Al alloys (atomic fraction) by Induction Skull Melting. The element Ce of 1.0 atomic percent was added individually, and La of 0.2 atomic percent was added individually. This article studied the influences of rare earth metal (Ce, La) on microstructure of as cast TiAl based alloy by XRD, SEM, EMPA and TEM measurement methodology. The results show that most of rare earth rich phases (AlCe, AlLa) are uniformly distributed in grain boundary in the shape of discontinuous network, and some particles of rare earth rich phases within the grains are mainly ellipsoids. In addition, rare earth element can obviously refine the grain size and the lamellar thickness of as cast TiAl based alloy samples. The grain size of Ti 47Al 1.0Ce 0.2La alloy reaches about 30～80 μm, and the lamellar thickness of its γ phase and α 2 phase are less than 200 and 20 nm, respectively.展开更多
Short chain branching has been characterized using thermal fractionation, a stepwise isothermal crystallizationtechnique, followed by a melting analysis scan using differential scanning calorimetry. Short chain branch...Short chain branching has been characterized using thermal fractionation, a stepwise isothermal crystallizationtechnique, followed by a melting analysis scan using differential scanning calorimetry. Short chain branching distributionwas also characterized by a continuous slow cooling crystallization, followed by a melting analysis scan. Four differentpolyethylenes were studied: Ziegler-Natta gas phase, Ziegler-Natta solution, metallocene, constrained-geometry single sitecatalyzed polyethylenes. The branching distribution was calculated from a calibration of branch content with meltingtemperature. The lamellar thickness was calculated based on the thermodynamic melting temperature of each polyethyleneand the surface free energy of the crystal face. The branching distribution and lamellar thickness distribution were used tocalculate weight average branch content, mean lamellar thickness, and a branch dispersity index. The results for the branchcontent were in good agreement with the known comonomer content of the polyethylenes. A limitation was that high branchcontent polyethylenes did not reach their potential crystallization at ambient temperatures. Cooling to sub-ambient wasnecessary to equilibrate the crystallization, but melting temperature versus branch content was not applicable after cooling tobelow ambient because the calibration data were not performed in this way.展开更多
The microstructures of the as-rolled magnesium alloy subjected to dynamic plastic deformation along the rolling direction have been investigated.Mostly one{101-2}twin variant or a twin variant pair is activated in a g...The microstructures of the as-rolled magnesium alloy subjected to dynamic plastic deformation along the rolling direction have been investigated.Mostly one{101-2}twin variant or a twin variant pair is activated in a grain,leading to a parallel{101-2}twin lamellar structure.At the stage of twinning-dominated deformation(ε〈-8%),lamellar thickness decreases significantly with strain,from 5.55 to 2.49 pro.The evolution of lamellar thickness during deformation is directly related to{1012}twin activity.When plastic strain is greater than-8%,the twin lamellar structure disappears because the volume fraction of twins almost saturates at a value of-90%.展开更多
Crystallization of flexible polymer chains reveals distinct characters compared to small molecules, which provides a platform to study molecular self-assembly and morphogenesis. In this review, some examples, e.g., tw...Crystallization of flexible polymer chains reveals distinct characters compared to small molecules, which provides a platform to study molecular self-assembly and morphogenesis. In this review, some examples, e.g., twisting chirality of polymer lamellar crystals, recognition of different chain units and competitive nucleation of different polymorphs and different lamellar thicknesses are briefly discussed. It is shown that the polymer crystallization process far from equilibrium is in practically minimization of the system free energy in local space and finite time, leading to formation of twisted crystals, metastable polymorphism and lamellar crystals with finite thickness. Though each molecule is blind to others, the peculiar ordered configurations with stronger long-range interactions are chosen from the enormous random trials. At the end, we list some remaining questions and outlook the perspectives.展开更多
The stereo-defects distribution of polypropylene of the two industry biaxially oriented polypropylene （BOPP） samples T28FE and F28SO with different processing properties was studied through successive self-nucleatio...The stereo-defects distribution of polypropylene of the two industry biaxially oriented polypropylene （BOPP） samples T28FE and F28SO with different processing properties was studied through successive self-nucleation and annealing （SSA） technique. It was found that there were more medium isotactic components in sample F28SO, and the isotactic sequence length of polypropylene of sample F28SO was shorter and the isotactic sequence length distribution of polypropylene of sample F28SO was broader, which could be processed well at high-speed orientation during the processing of BOPP films. This result indicates that the isotactic sequence length distribution of polypropylene is related to the processing speed during preparing BOPP films, and the stereo-defects distribution of polypropylene has an important influence on its processing ability.展开更多
基金Natural Science Foundation of Liaoning Province,China(No.20042081)
文摘AIMTo determine the effect of suction duration on thickness and diameter of corneal flap created by microkeratome in porcine eyes in laser in situ keratomileusis (LASIK).
文摘The rare earth (RE) elements (Ce, La) were added to binary Ti 47% Al alloys (atomic fraction) by Induction Skull Melting. The element Ce of 1.0 atomic percent was added individually, and La of 0.2 atomic percent was added individually. This article studied the influences of rare earth metal (Ce, La) on microstructure of as cast TiAl based alloy by XRD, SEM, EMPA and TEM measurement methodology. The results show that most of rare earth rich phases (AlCe, AlLa) are uniformly distributed in grain boundary in the shape of discontinuous network, and some particles of rare earth rich phases within the grains are mainly ellipsoids. In addition, rare earth element can obviously refine the grain size and the lamellar thickness of as cast TiAl based alloy samples. The grain size of Ti 47Al 1.0Ce 0.2La alloy reaches about 30～80 μm, and the lamellar thickness of its γ phase and α 2 phase are less than 200 and 20 nm, respectively.
文摘Short chain branching has been characterized using thermal fractionation, a stepwise isothermal crystallizationtechnique, followed by a melting analysis scan using differential scanning calorimetry. Short chain branching distributionwas also characterized by a continuous slow cooling crystallization, followed by a melting analysis scan. Four differentpolyethylenes were studied: Ziegler-Natta gas phase, Ziegler-Natta solution, metallocene, constrained-geometry single sitecatalyzed polyethylenes. The branching distribution was calculated from a calibration of branch content with meltingtemperature. The lamellar thickness was calculated based on the thermodynamic melting temperature of each polyethyleneand the surface free energy of the crystal face. The branching distribution and lamellar thickness distribution were used tocalculate weight average branch content, mean lamellar thickness, and a branch dispersity index. The results for the branchcontent were in good agreement with the known comonomer content of the polyethylenes. A limitation was that high branchcontent polyethylenes did not reach their potential crystallization at ambient temperatures. Cooling to sub-ambient wasnecessary to equilibrate the crystallization, but melting temperature versus branch content was not applicable after cooling tobelow ambient because the calibration data were not performed in this way.
基金supported by National Natural Science Foundation of China(Nos.51071183,50890170 and 51271208)the Fundamental Research Funds for the Central Universities(No.CDJXS11132225)
文摘The microstructures of the as-rolled magnesium alloy subjected to dynamic plastic deformation along the rolling direction have been investigated.Mostly one{101-2}twin variant or a twin variant pair is activated in a grain,leading to a parallel{101-2}twin lamellar structure.At the stage of twinning-dominated deformation(ε〈-8%),lamellar thickness decreases significantly with strain,from 5.55 to 2.49 pro.The evolution of lamellar thickness during deformation is directly related to{1012}twin activity.When plastic strain is greater than-8%,the twin lamellar structure disappears because the volume fraction of twins almost saturates at a value of-90%.
基金the National Natural Science Foundation of China (No. 21374054)Fund of Key Laboratory of Advanced Materials of Ministry of Education (No. 2017AML07) for financial support
文摘Crystallization of flexible polymer chains reveals distinct characters compared to small molecules, which provides a platform to study molecular self-assembly and morphogenesis. In this review, some examples, e.g., twisting chirality of polymer lamellar crystals, recognition of different chain units and competitive nucleation of different polymorphs and different lamellar thicknesses are briefly discussed. It is shown that the polymer crystallization process far from equilibrium is in practically minimization of the system free energy in local space and finite time, leading to formation of twisted crystals, metastable polymorphism and lamellar crystals with finite thickness. Though each molecule is blind to others, the peculiar ordered configurations with stronger long-range interactions are chosen from the enormous random trials. At the end, we list some remaining questions and outlook the perspectives.
基金financially supported by the National Natural Science Foundation of China(No.51073170)
文摘The stereo-defects distribution of polypropylene of the two industry biaxially oriented polypropylene （BOPP） samples T28FE and F28SO with different processing properties was studied through successive self-nucleation and annealing （SSA） technique. It was found that there were more medium isotactic components in sample F28SO, and the isotactic sequence length of polypropylene of sample F28SO was shorter and the isotactic sequence length distribution of polypropylene of sample F28SO was broader, which could be processed well at high-speed orientation during the processing of BOPP films. This result indicates that the isotactic sequence length distribution of polypropylene is related to the processing speed during preparing BOPP films, and the stereo-defects distribution of polypropylene has an important influence on its processing ability.
