This paper investigates the temperature field distribution and thermal focal length within a laser diode array （LDA） end-pumped YVO4/Nd：YVO4 rectangular composite crystal. A general expression of the temperature fi...This paper investigates the temperature field distribution and thermal focal length within a laser diode array （LDA） end-pumped YVO4/Nd：YVO4 rectangular composite crystal. A general expression of the temperature field distribution within the Nd：YVO4 rectangular crystal was obtained by analysing the characteristics of the Nd：YVO4 crystal and solving the Poisson equation with boundary conditions. The temperature field distributions in the Nd：YVO4 rectangular crystal for the YVO4/Nd：YVO4 composite crystal and the Nd：YVO4 single crystal are researched respectively. Calculating the thermal focal length within the Nd：YVO4 rectangular crystal was done by an analysis of the additional optical path differences （OPD） caused by heat, which was very identical with experimental results in this paper. Research results show that the maximum relative temperature on the rear face of the Nd：YVO4 crystal in the composite crystal is 150 K and the thermal focal length is 35.7mm when the output power of the LDA is 22 W. In the same circumstances, the experimental value of the thermal focal length is 37.4 mm. So the relative error between the theoretical analysis and the experimental result is only 4.5%. With the same conditions, the thermal focal length of the Nd：YVO4 single crystal is 18.5 mm. So the relative rate of the thermal focal length between the YVO4/Nd：YVO4 crystal and the Nd：YVO4 crystal is 93%. So, the thermal stability of the output power and the beam quality of the YVO4/Nd：YVO4 laser is more advantageous than the laser with Nd：YVO4 single crystal.展开更多
A type of As2S3 chalcogenide glass mid-infrared dual-core photonic crystal fiber has been proposed. The dualcore photonic crystal fiber （PCF） consists of two asymmetric cores. The high polarization property and the ...A type of As2S3 chalcogenide glass mid-infrared dual-core photonic crystal fiber has been proposed. The dualcore photonic crystal fiber （PCF） consists of two asymmetric cores. The high polarization property and the coupling characteristics have been studied by using the finite dement method and mode coupling theory. Numerical results show that the birefringence at wavelength λ = 10 μm is up to 0.01386 and the coupling length can reach wavelength = 5 μm, 261 μm and 271.44 μm for x-polarized mode and y-polarized mode, respectively. It demonstrates that a 6.786-ram-long fiber can exhibit an extinction ratio of better than -10 dB and a bandwidth of 180 nm.展开更多
To study the extraction difficulty of lithium ions from various crystal planes of Li2 TiO3, according to the first principle, four representative crystal surfaces of Li2TiO3（precursor）,（-133）,（-206）,（002） and...To study the extraction difficulty of lithium ions from various crystal planes of Li2 TiO3, according to the first principle, four representative crystal surfaces of Li2TiO3（precursor）,（-133）,（-206）,（002） and（-131）, were selected to establish a model and to calculate the surface energy, bond length and population using Materials Studio 5.5（MS 5.5）. The results demonstrate that there is no direct relationship between the surface energy and the order of disappearance of the four diffraction peaks when lithium titanate is treated with hydrochloric acid, instead, the difficulty of Li~＋ extraction from various crystal faces corresponds to the Li-O bond strength. Lithium ion is easy to remove from（-133） and（-206） due to the relatively weak Li-O bond strength. In contrast, Li＋ extraction requires a longer time for（002） and（-131）.展开更多
The molecular structure of polyethylene (PE) samples with various comonomers including propylene, I-butane and 1-hexene was investigated by DSC and C-13-NMR techniques. The density of the samples varies from 0.948 g/c...The molecular structure of polyethylene (PE) samples with various comonomers including propylene, I-butane and 1-hexene was investigated by DSC and C-13-NMR techniques. The density of the samples varies from 0.948 g/cm(3) to 0.917 g/cm(3), and the molecular weight determined by the GPC method is in the range of 1 similar to2 x 10(5). The branch paint content of the samples was determined by C-13-NMR measurements and was found to be less than 20 per 1000 C atoms along the main chain. Crystallization segregation DSC technique (CSDSC) was used to characterize the branch point distribution or the segment length distribution of PEs. The crystallization segregation was performed in a successive annealing process at decreasing temperatures. The interval of two successive annealing temperatures was 6 K, and the time length of each annealing step was 2.5 h. The CSDSC results clearly indicate that all the PE samples used, including some metallocene PEs, more or less exhibit their non-uniformity in segment length distribution, and bimodal or multimodal CSDSC curves were usually observed. For quantitative characterization of the CSDSC curves and the segment length distribution two parameters, the average melting point, T-mAV, and the root-mean-square deviation of melting temperature, (DeltaT(m)(AV)(2))(1/2), were proposed. TmAV is corresponding to the average segment length due to branching and (DeltaT(m)(AV)(2))(1/2) gives information about the: width of the segment length distribution. Experimental results show that both the degree of average melting temperature depression and the width of the distribution seem to increase with increasing the branching content and are dependent on the type of comonomers. Very good reproducibility and additivity of the CSDSC method were evidenced experimentally. It was concluded that the CSDSC technique is a sensitive and convenient method for characterizing the segment length distribution of branched polyethylenes and will be of great interest in structure-property relationship studies of crystalline polymers.展开更多
In manufacturing process, it is necessary to measure change in CSD (Crystal Size Distribution) with time accurately because CSD is one of the most important indices that evaluate quality of products. FBRM (Focused Bea...In manufacturing process, it is necessary to measure change in CSD (Crystal Size Distribution) with time accurately because CSD is one of the most important indices that evaluate quality of products. FBRM (Focused Beam Reflectance Measurement) can measure CLD (Chord Length Distribution) in line, but CLD is different from CSD because of principle of FBRM. However, if CSD is determined beforehand, CLD can be calculated from the CSD with statistical method. First, when crystal shape is defined from the characteristic crystal size, the matrix of each crystal shape which transforms CSD into CLD in a uniform manner is calculated with Monte Carlo analysis. Characteristic crystal size is added to the variables defining chord length in order to avoid complex integrals and apply the change in crystal shape with characteristic crystal size to the transforming matrix. Secondly, CSD and CLD are actually measured in suspension of acetaminophen in ethanol and suspension of L-arginine in water to demonstrate the validity of 2 matrices. Lastly, these matrices are multiplied by some simple CSD models to test the properties of these matrices and demonstrate the utility of this transformation.展开更多
A statistical distribution function of the dislocation link length,in unit volume of the crystalline materials has been derived theoretically after semi-infinite normalization by as- suming the distribution of actual ...A statistical distribution function of the dislocation link length,in unit volume of the crystalline materials has been derived theoretically after semi-infinite normalization by as- suming the distribution of actual links in all positions of crystalline materials with equal prob- ability,i.e. (l)dl=2ρl_γ^(-4)l^2exp(l^2/l_γ~2)dl where ρ is dislocation density,This assumption seems to be reasonable for polycrystalline fec metallic materials,and confirmation has been found in pure Ni and stainless steel 1Cr18Ni9Ti TEM experiments alresults.展开更多
This paper presents a method to measure the spontaneous extension of oriented PET fibredirectly during crystallization by twice annealing (constant-length and free-length). Samples be-fore and after the treatment were...This paper presents a method to measure the spontaneous extension of oriented PET fibredirectly during crystallization by twice annealing (constant-length and free-length). Samples be-fore and after the treatment were collected and examined by X-ray diffraction, DSC andbirefringence. The crystallinity, crystallite size, and orientation of both crystalline and amorphousparts between these samples are changed greatly which show that the extension is a consequence ofcrystallization and reorientation of uncrystallized segments along the fibre direction. The results ofthis study are not only important to understand the mechanism of supermolecular structurechanges during crystallization, but also useful to the industrial technology of crystallization spin-ning.展开更多
文摘This paper investigates the temperature field distribution and thermal focal length within a laser diode array （LDA） end-pumped YVO4/Nd：YVO4 rectangular composite crystal. A general expression of the temperature field distribution within the Nd：YVO4 rectangular crystal was obtained by analysing the characteristics of the Nd：YVO4 crystal and solving the Poisson equation with boundary conditions. The temperature field distributions in the Nd：YVO4 rectangular crystal for the YVO4/Nd：YVO4 composite crystal and the Nd：YVO4 single crystal are researched respectively. Calculating the thermal focal length within the Nd：YVO4 rectangular crystal was done by an analysis of the additional optical path differences （OPD） caused by heat, which was very identical with experimental results in this paper. Research results show that the maximum relative temperature on the rear face of the Nd：YVO4 crystal in the composite crystal is 150 K and the thermal focal length is 35.7mm when the output power of the LDA is 22 W. In the same circumstances, the experimental value of the thermal focal length is 37.4 mm. So the relative error between the theoretical analysis and the experimental result is only 4.5%. With the same conditions, the thermal focal length of the Nd：YVO4 single crystal is 18.5 mm. So the relative rate of the thermal focal length between the YVO4/Nd：YVO4 crystal and the Nd：YVO4 crystal is 93%. So, the thermal stability of the output power and the beam quality of the YVO4/Nd：YVO4 laser is more advantageous than the laser with Nd：YVO4 single crystal.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10874145)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20091333110010)+1 种基金the Natural Science Foundation of Hebei Province, China (Grant No. F2009000481)the China Postdoctoral Science Foundation (Grant Nos. 20080440014 and 200902046)
文摘A type of As2S3 chalcogenide glass mid-infrared dual-core photonic crystal fiber has been proposed. The dualcore photonic crystal fiber （PCF） consists of two asymmetric cores. The high polarization property and the coupling characteristics have been studied by using the finite dement method and mode coupling theory. Numerical results show that the birefringence at wavelength λ = 10 μm is up to 0.01386 and the coupling length can reach wavelength = 5 μm, 261 μm and 271.44 μm for x-polarized mode and y-polarized mode, respectively. It demonstrates that a 6.786-ram-long fiber can exhibit an extinction ratio of better than -10 dB and a bandwidth of 180 nm.
基金Funded partly by the Key Project of Natural Science of Sichuan Provincial Education Department(No.16ZA0309)the Doctoral Research Start-up Funding(No.15B16)
文摘To study the extraction difficulty of lithium ions from various crystal planes of Li2 TiO3, according to the first principle, four representative crystal surfaces of Li2TiO3（precursor）,（-133）,（-206）,（002） and（-131）, were selected to establish a model and to calculate the surface energy, bond length and population using Materials Studio 5.5（MS 5.5）. The results demonstrate that there is no direct relationship between the surface energy and the order of disappearance of the four diffraction peaks when lithium titanate is treated with hydrochloric acid, instead, the difficulty of Li~＋ extraction from various crystal faces corresponds to the Li-O bond strength. Lithium ion is easy to remove from（-133） and（-206） due to the relatively weak Li-O bond strength. In contrast, Li＋ extraction requires a longer time for（002） and（-131）.
基金This work was supported by the Science Foundation of Polymer Physics Laboratory, Chinese Academy of Sciences.
文摘The molecular structure of polyethylene (PE) samples with various comonomers including propylene, I-butane and 1-hexene was investigated by DSC and C-13-NMR techniques. The density of the samples varies from 0.948 g/cm(3) to 0.917 g/cm(3), and the molecular weight determined by the GPC method is in the range of 1 similar to2 x 10(5). The branch paint content of the samples was determined by C-13-NMR measurements and was found to be less than 20 per 1000 C atoms along the main chain. Crystallization segregation DSC technique (CSDSC) was used to characterize the branch point distribution or the segment length distribution of PEs. The crystallization segregation was performed in a successive annealing process at decreasing temperatures. The interval of two successive annealing temperatures was 6 K, and the time length of each annealing step was 2.5 h. The CSDSC results clearly indicate that all the PE samples used, including some metallocene PEs, more or less exhibit their non-uniformity in segment length distribution, and bimodal or multimodal CSDSC curves were usually observed. For quantitative characterization of the CSDSC curves and the segment length distribution two parameters, the average melting point, T-mAV, and the root-mean-square deviation of melting temperature, (DeltaT(m)(AV)(2))(1/2), were proposed. TmAV is corresponding to the average segment length due to branching and (DeltaT(m)(AV)(2))(1/2) gives information about the: width of the segment length distribution. Experimental results show that both the degree of average melting temperature depression and the width of the distribution seem to increase with increasing the branching content and are dependent on the type of comonomers. Very good reproducibility and additivity of the CSDSC method were evidenced experimentally. It was concluded that the CSDSC technique is a sensitive and convenient method for characterizing the segment length distribution of branched polyethylenes and will be of great interest in structure-property relationship studies of crystalline polymers.
文摘In manufacturing process, it is necessary to measure change in CSD (Crystal Size Distribution) with time accurately because CSD is one of the most important indices that evaluate quality of products. FBRM (Focused Beam Reflectance Measurement) can measure CLD (Chord Length Distribution) in line, but CLD is different from CSD because of principle of FBRM. However, if CSD is determined beforehand, CLD can be calculated from the CSD with statistical method. First, when crystal shape is defined from the characteristic crystal size, the matrix of each crystal shape which transforms CSD into CLD in a uniform manner is calculated with Monte Carlo analysis. Characteristic crystal size is added to the variables defining chord length in order to avoid complex integrals and apply the change in crystal shape with characteristic crystal size to the transforming matrix. Secondly, CSD and CLD are actually measured in suspension of acetaminophen in ethanol and suspension of L-arginine in water to demonstrate the validity of 2 matrices. Lastly, these matrices are multiplied by some simple CSD models to test the properties of these matrices and demonstrate the utility of this transformation.
文摘A statistical distribution function of the dislocation link length,in unit volume of the crystalline materials has been derived theoretically after semi-infinite normalization by as- suming the distribution of actual links in all positions of crystalline materials with equal prob- ability,i.e. (l)dl=2ρl_γ^(-4)l^2exp(l^2/l_γ~2)dl where ρ is dislocation density,This assumption seems to be reasonable for polycrystalline fec metallic materials,and confirmation has been found in pure Ni and stainless steel 1Cr18Ni9Ti TEM experiments alresults.
文摘This paper presents a method to measure the spontaneous extension of oriented PET fibredirectly during crystallization by twice annealing (constant-length and free-length). Samples be-fore and after the treatment were collected and examined by X-ray diffraction, DSC andbirefringence. The crystallinity, crystallite size, and orientation of both crystalline and amorphousparts between these samples are changed greatly which show that the extension is a consequence ofcrystallization and reorientation of uncrystallized segments along the fibre direction. The results ofthis study are not only important to understand the mechanism of supermolecular structurechanges during crystallization, but also useful to the industrial technology of crystallization spin-ning.
