Machine learning methodologies have been extensively leveraged across diverse domains of chemical research,yielding remarkable outcomes,and exhibit substantial potential for impactful future applications within the fi...Machine learning methodologies have been extensively leveraged across diverse domains of chemical research,yielding remarkable outcomes,and exhibit substantial potential for impactful future applications within the field of supramolecular chemistry.The recognition of alkali metal ions by crown ethers is one of the most classic and widely applied host-vip interactions in supramolecular chemistry.Due to the numerous factors affecting the host-vip interaction,it remains a great challenge to achieve fast and accurate prediction of the binding constants between crown ethers and alkali metal ions.Herein,we report a highly accurate machine learning model that can effectively predict the binding constants between crown ethers and alkali metal ions,i.e.,CrownBind-IA,with a low RMSE of 0.68 logK units.Moreover,this model proves robust extrapolative capabilities by accurately predicting out-of-sample data.The establishment of CrownBind-IA demonstrates the promising application potentials of data-driven machine learning methods in supramolecular chemistry,and it will substantially reduce the time and expense of experimental trials and characterizations,promote the exploration of the mechanism of host-vip interactions,as well as the rational design of novel functional supramolecular host molecules.展开更多
The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of thre...The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of three isomers lead to di-verse dipole moments and spectro-scopic constants.The anharmonic force field and spectroscopic con-stants of thiocarbonyl thioketen and its isomers are calculated using MP2,B3LYP,and CCSD(T)methods employing correlation consistent basis sets.Molecule structures,rotational spectroscopic constants,and fundamental frequencies are compared with the available experimental data for thiocarbonyl thioketen.Ro-vibrational interaction constants,anharmonic constants,cubic and quartic force constants are predicted for thiocarbonyl thioketen.In addition,some rotational and vibrational spectroscopic parameters are predict-ed with the same level of theory for thioacetylene,HCCSH,and thiirene,(CH)_(2)S.The predic-tions of these spectroscopic constants are expected to guide the future astronomical observa-tion and high resolution experimental work for C_(2)H_(2)S isomers.展开更多
Poly(m-phenylene isophthalamide)(PMIA),a key aromatic polyamide,is widely used for its outstanding mechanical strength,high thermal stability,and excellent insulation properties.However,different applications demand v...Poly(m-phenylene isophthalamide)(PMIA),a key aromatic polyamide,is widely used for its outstanding mechanical strength,high thermal stability,and excellent insulation properties.However,different applications demand varying dielectric properties,so tailoring its dielectric per-formance is essential.PMIA was first synthesized in this study,followed by introducing pores and developing porous PMIA films and PMIA-based composites with reduced dielectric constants.Porous PMIA films were fabricated using the wet phase inversion process with N,N-dimethylac-etamide(DMAC)solvent and water as the non-solvent.The impact of casting solution composi-tion and coagulation bath temperature on pore structures was analyzed.A film produced with 18%PMIA and 5%LiCl in a 35℃coagulation bath achieved the lowest dielectric constant of 1.76 at 1 Hz,48%lower than the standard PMIA film,which had a tensile strength of 18.5 MPa and an initial degradation temperature of 320℃.展开更多
Effects of initial δ phase（Ni_3Nb） on the hot tensile deformation behaviors and material constants of a Ni-based superalloy were investigated over wide ranges of strain rate and deformation temperature. It is found...Effects of initial δ phase（Ni_3Nb） on the hot tensile deformation behaviors and material constants of a Ni-based superalloy were investigated over wide ranges of strain rate and deformation temperature. It is found that the true stress-true strain curves exhibit peak stress at a small strain, and the peak stress increases with the increase of initial δ phase. After the peak stress, initial δ phase promotes the dynamic softening behaviors, resulting in the decreased flow stress. An improved Arrhenius constitutive model is proposed to consider the synthetical effects of initial δ phase, deformation temperature, strain rate, and strain on hot deformation behaviors. In the improved model, material constants are expressed as the functions of the content of initial δ phase and strain. A good agreement between the predicted and measured results indicates that the improved Arrhenius constitutive model can well describe hot deformation behaviors of the studied Ni-based superalloy.展开更多
The positive and negative difference of deep and shallow resisitivity in formation without invasion is caused mainly by the fixed two tool constants from numerical simulations. A dynamic calibration method for tool co...The positive and negative difference of deep and shallow resisitivity in formation without invasion is caused mainly by the fixed two tool constants from numerical simulations. A dynamic calibration method for tool constants is proposed based on the effects of the mud and formation resisitivity ratio on the two constants calculated using the finite element method （FEM）. Finally, four specific examples are given to validate the dynamic calibration method. It is an automatic borehole correction method and can give more accurate formation resistivity. The method is useful for dual laterolog logging.展开更多
This paper presents an experimental study to determine the tensile properties of the envelope fabric Uretek3216L under biaxial cyclic loading.First the biaxial cyclic tests were carefully carried out on the envelope m...This paper presents an experimental study to determine the tensile properties of the envelope fabric Uretek3216L under biaxial cyclic loading.First the biaxial cyclic tests were carefully carried out on the envelope material to obtain the stress-strain data and the corresponding nonlinearity and orthotropy of the material were analyzed. Then for some determination options with different stress ratios the least squares method minimizing the strain terms was used to calculate the elastic constants from the experimental data.Finally the influences of the determination options with different stress ratios and the reciprocal relationship on the elastic constants were discussed.Results show that the orthotropy of the envelope material can be attributed to the unbalanced crimp of their constitutive yarns in warp and weft directions and the elastic constants vary noticeably with the determination options as well as the normalized stress ratios.In real design practice it is more reasonable to use constants determined for specific stress states in particular stress ratios depending on the project＆#39;s needs.Also calculating the structures with two limitative sets of elastic constants instead of using only one set is recommendable in light of the great variety of the constant＆#39;s values.展开更多
Based on previous laser-induced fluorescence excitation spectroscopy work, the vibrational constants of neutral FeS in the X5 △ electronic state were obtained by directly mapping the ground-state vibrational levels u...Based on previous laser-induced fluorescence excitation spectroscopy work, the vibrational constants of neutral FeS in the X5 △ electronic state were obtained by directly mapping the ground-state vibrational levels up to v＂=3 using conventional laser-induced dispersed fluorescence spectroscopy. The vibrational frequency of FeS（X5 △） （518±5 cm-1） agrees well with that reported in a recent PES measurement （520±30 cm-1） [J. Phys. Chem. A 107, 2821 （2003）] which is the only one prior experimental vibrational frequency value for the 5 △ state of FeS. Careful comparisons of our experimental results and those documented in the literature （mainly from theoretical predictions） suggest that the ground state of FeS is 5 △ state.展开更多
The cadmium（Ⅱ）-glycine system was studied by the two experimental techniques, ion sensitive electrode （ISE） and differential pulse polarography （DPP）, and the experimental data obtained were used by a unified m...The cadmium（Ⅱ）-glycine system was studied by the two experimental techniques, ion sensitive electrode （ISE） and differential pulse polarography （DPP）, and the experimental data obtained were used by a unified mathematical treatment to calculate the complex stability constants. The combination of the two techniques is of many advantages as ISE can be performed at low [LT]：[MT] ratios and significantly higher [MT], whereas DPP could be used well at large [LT]：[MT] ratios and much smaller [MT]. This makes it possible to study a metal-ligand system in a relatively broader range of experimental conditions that, in turn, provides more information about the metakligand system of interest. Applying the unified mathematical treatment to the cadmium-glycine system, two new complexes MHL and ML2（OH） as well as three complexes ML, ML2 and ML3, reported in literatures, could be modeled and all their stability constants have been refined.展开更多
By double beam and double wave interferomatric (DDI) method, the optical constants of thin films, i.e. refractive index, extinction coefficient and thickness may be determined in infrared (3.39 μm) and in visible (...By double beam and double wave interferomatric (DDI) method, the optical constants of thin films, i.e. refractive index, extinction coefficient and thickness may be determined in infrared (3.39 μm) and in visible (0.633 μm) wavelengths in the same optical path with a tunable double wave He Ne laser designed by ourselves. The measuring principle and the device are describod.展开更多
AIM: To evaluate the effect of different lens constant optimization methods on the accuracy of intraocular lens(IOL) power calculation formulas for highly myopic eyes.METHODS: This study comprised 108 eyes of 94 conse...AIM: To evaluate the effect of different lens constant optimization methods on the accuracy of intraocular lens(IOL) power calculation formulas for highly myopic eyes.METHODS: This study comprised 108 eyes of 94 consecutive patients with axial length(AL) over 26 mm undergoing phacoemulsification and implantation of a Rayner(Hove, UK) 920H IOL. Formulas were evaluated using the following lens constants: manufacturer’s lens constant, User Group for Laser Interference Biometry(ULIB) constant, and optimized constant for long eyes. Results were compared with Barrett Universal II formula, original Wang-Koch AL adjustment method, and modified Wang-Koch AL adjustment method. The outcomes assessed were mean absolute error(MAE) and percentage of eyes with IOL prediction errors within ±0.25, ±0.50, and ±1.0 diopter(D). The nonparametric method, Friedman test, was used to compare MAE performance among constants.RESULTS: Optimized constants could significantly reduce the MAE of SRK/T, Hoffer Q, and Holladay 1 formulas compared with manufacturer’s lens constant, whereas the percentage of eyes with IOL prediction errors within ±0.25, ±0.50, and ±1.0 D had no statistically significant differences. Optimized lens constant for long eyes alone showed non-significant refractive advantages over the ULIB constant. Barrett Universal II formula and formulas with AL adjustment showed significantly higher accuracy in highly myopic eyes(P<0.001). CONCLUSION: Lens constant optimization for the subset of long eyes reduces the refractive error only to a limited extent for highly myopic eyes.展开更多
The binding of Tb 3+ to chicken apoovotransferrin was studied by monitoring the fluorescent intensity of Tb 3+ at 549 nm. The conditional equilibrium constants for the complexation of Tb 3+ by chicken apoovotransferri...The binding of Tb 3+ to chicken apoovotransferrin was studied by monitoring the fluorescent intensity of Tb 3+ at 549 nm. The conditional equilibrium constants for the complexation of Tb 3+ by chicken apoovotransferrin in 0 1 mol/L hepes, at pH 7 4 and room temperature were measured. The successive macroscopic binding constants are lg K 1=9 08±0 12 and lg K 2=7 36±0 22. The molar fluorescence enhancement of Tb 3+ apoovotransferrin complex is (2 06±0 14)×10 4 mol -1 ·L. The fluorescence quenching experiment and the titration of N terminal monoferric ovotransferrin showed that Tb 3+ has a preference for being bound to the N terminal binding site of apoovotransferrin.展开更多
Thin oxidized copper films in various thickness values are deposited onto quartz glass substrates by electron beam evaporation. The ellipsometry parameters and transmittance in a wavelength range of 300 nm-1000 nm are...Thin oxidized copper films in various thickness values are deposited onto quartz glass substrates by electron beam evaporation. The ellipsometry parameters and transmittance in a wavelength range of 300 nm-1000 nm are collected by a spectroscopic ellipsometer and a spectrophotometer respectively. The effective thickness and optical constants, i.e., refractive index n and extinction coefficient k, are accurately determined by using newly developed ellipsometry combined with transmittance iteration method. It is found that the effective thickness determined by this method is close to the physical thickness and has obvious difference from the mass thickness for very thin film due to variable density of film. Furthermore, the thickness dependence of optical constants of thin oxidized Cu films is analyzed.展开更多
The density functional theory （B3LYP, B3P86） and the quadratic configuration-interaction method including single and double substitutions （QCISD（T）, QCISD） presented in Gaussian03 program package are employed to...The density functional theory （B3LYP, B3P86） and the quadratic configuration-interaction method including single and double substitutions （QCISD（T）, QCISD） presented in Gaussian03 program package are employed to calculate the equilibrium internuclear distance Re, the dissociation energy De and the harmonic frequency We for the XIEg＋ state of sodium dimer in a number of basis sets. The conclusion is gained that the best Re, De and We results can be attained at the QCISD/6-311G（3df,3pd） level of theory. The potential energy curve at this level of theory for this state is obtained over a wide internuclear separation range from 0.16 to 2.0 nm and is fitted to the analytic Murrell-Sorbie function. The spectroscopic parameters De, DO, Re, ωe, ωe Xe, αe and Be are calculated to be 0.7219 eV, 0.7135 eV, 0.31813 nm, 151.63 cm^-1, 0.7288 cm^-1, 0.000729 cm^-1 and 0.1449 cm^-1, respectively, which are in good agreement with the measurements. With the potential obtained at the QCISD/6-311G（3df,3pd） level of theory, a total of 63 vibrational states is found when J = 0 by solving the radial SchrSdinger equation of nuclear motion. The vibrational level, corresponding classical turning point and inertial rotation constant are computed for each vibrational state. The centrifugal distortion constants （Dr Hv, Lv, Mv, Nv and Ov） are reported for the first time for the first 31 vibrational states when J = 0.展开更多
Ab initio VB calculations were used to determine the accurate spectroscopic parameters of the ground states of LiF and NaF. A set of potential energy curves corresponding to the ground states including ionic and cov...Ab initio VB calculations were used to determine the accurate spectroscopic parameters of the ground states of LiF and NaF. A set of potential energy curves corresponding to the ground states including ionic and covalent interactions, pure ionic interaction and covalent interaction were generated using the VBSCF method. Curve crossing in the dissociation processes of LiF and NaF was discussed. The optimized VB wave functions suggest that LiF and NaF are of high ionicity, and their ionic weights are 86 2% and 94 6%, respectively. NaF has a higher ionicity. The main difference between atom F and ion F - and the effect of the proper description of this difference on dissociation energies were investigated.展开更多
A three-phase confocal elliptical cylinder model is proposed to analyze micromechanics of one-dimensional hexagonal piezoelectric quasicrystal （PQC） compos- ites. Exact solutions of the phonon, phason, and electric ...A three-phase confocal elliptical cylinder model is proposed to analyze micromechanics of one-dimensional hexagonal piezoelectric quasicrystal （PQC） compos- ites. Exact solutions of the phonon, phason, and electric fields are obtained by using the conformal mapping combined with the Laurent expansion technique when the model is subject to far-field anti-plane mechanical and in-plane electric loadings. The effective elec- troelastic constants of several different composites made up of PQC, quasicrystal （QC）, and piezoelectric （PE） materials are predicted by the generalized self-consistent method. Numerical examples are conducted to show the effects of the volume fraction and the cross-sectional shape of inclusion （or fiber） on the effective electroelastic constants of these composites. Compared with other micromechanical methods, the generalized self- consistent and Mori-Tanaka methods can predict the effective electroelastic constants of the composites consistently.展开更多
The definitions of the third-order elastic,piezoelectric,and dielectric constants and the properties of the associated tensors are discussed.Based on the energy conservation and coordinate transformation,the relations...The definitions of the third-order elastic,piezoelectric,and dielectric constants and the properties of the associated tensors are discussed.Based on the energy conservation and coordinate transformation,the relations among the third-order constants are obtained.Furthermore,the relations among the third-order elastic,piezoelectric,and dielectric constants of the seven crystal systems and isotropic materials are listed in detail.These third-order constants relations play an important role in solving nonlinear problems of elastic and piezoelectric materials.It is further found that all third-order piezoelectric constants are 0 for 15 kinds of point groups,while all third-order dielectric constants are 0 for 16 kinds of point groups as well as isotropic material.The reason is that some of the point groups are centrally symmetric,and the other point groups are high symmetry.These results provide the foundation to measure these constants,to choose material,and to research nonlinear problems.Moreover,these results are helpful not only for the study of nonlinear elastic and piezoelectric problems,but also for the research on flexoelectric effects and size effects.展开更多
To investigate the origin of the strong dependence of martensitic transformation temperature on composition, the elastic properties of high temperature B2 phases of both NiTi and NiAI were calculated by a first-princi...To investigate the origin of the strong dependence of martensitic transformation temperature on composition, the elastic properties of high temperature B2 phases of both NiTi and NiAI were calculated by a first-principle method, the exact-muffin orbital method within coherent potential approximation. In the composition range of 50-56 at. pct Ni of NiTi and 60-70 at. pct Ni of NiAI in which martensitic transformation occurs, non-basalplane shear modulus c44 increases with increasing Ni content, while basal-plane shear modulus c＇ decreases. In the above composition ranges however the transformation temperature of NiAI increases with increasing Ni content while that of NiTi decreases from experimental observation. The softening of c＇ is experimentally observed only in NiAI, and the decrease of c＇ with increasing Ni content is responsible for the increase of transformation temperature. The result of the present work demonstrates that, besides c＇, c44 also influences the martensitic transformation of NiTi and plays quite important a role.展开更多
The protonation constants of a new dinucleating 24-membered hexaazadiphenol macrocyclic ligand, BDBPH, were determined by potentiometric measurement at 25.0 degreesC and mu = 0.100 mol.L-1 (KCl). The species distribut...The protonation constants of a new dinucleating 24-membered hexaazadiphenol macrocyclic ligand, BDBPH, were determined by potentiometric measurement at 25.0 degreesC and mu = 0.100 mol.L-1 (KCl). The species distributions of the deprotonated and protonated compounds in the pH range from 2 to 12 aqueous solutions were also described.展开更多
The angular light-scattering measurement（ALSM） method combined with an improved artificial bee colony algorithm is introduced to determine aerosol optical constants and aerosol size distribution（ASD） simultaneousl...The angular light-scattering measurement（ALSM） method combined with an improved artificial bee colony algorithm is introduced to determine aerosol optical constants and aerosol size distribution（ASD） simultaneously. Meanwhile, an optimized selection principle of the ALSM signals based on the sensitivity analysis and principle component analysis（PCA）is proposed to improve the accuracy of the retrieval results. The sensitivity analysis of the ALSM signals to the optical constants or characteristic parameters in the ASD is studied first to find the optimized selection region of measurement angles. Then, the PCA is adopted to select the optimized measurement angles within the optimized selection region obtained by sensitivity analysis. The investigation reveals that, compared with random selection measurement angles, the optimized selection measurement angles can provide more useful measurement information to ensure the retrieval accuracy. Finally,the aerosol optical constants and the ASDs are reconstructed simultaneously. The results show that the retrieval accuracy of refractive indices is better than that of absorption indices, while the characteristic parameters in ASDs have similar retrieval accuracy. Moreover, the retrieval accuracy in studying L-N distribution is a little better than that in studying Gamma distribution for the difference of corresponding correlation coefficient matrixes of the ALSM signals. All the results confirm that the proposed technique is an effective and reliable technique in estimating the aerosol optical constants and ASD simultaneously.展开更多
The Al film reflectors can yield a high-reflectance over a broad wavelength region, and have been widely used in the spacecraft optical instruments for high quality optical applications. Under the irradiation of charg...The Al film reflectors can yield a high-reflectance over a broad wavelength region, and have been widely used in the spacecraft optical instruments for high quality optical applications. Under the irradiation of charged particles in the Earth radiation belt, the reflectors could be deteriorated. In order to reveal the deterioration mechanism, the change in optical constants of Al film reflector induced by proton radiation with 60 keV was studied in an environment of vacuum with heat sink. Experimental results showed that when the radiation damage primarily occurs in the Al reflecting film, the extinction coefficient k will gradually decrease with increasing radiation fluence, which results in the decrease of the energies of reflective light. Therefore, the proton radiation induced an obvious degradation of spectral reflectance in the wavelength region from 200 to 800nm on the Al film reflector.展开更多
基金the financial support of the National Natural Science Foundation of China(Nos.22193020 and 22193022)the financial support of the National Natural Science Foundation of China(No.32301691)+4 种基金Tsinghua University Initiative Scientific Research Programthe financial support of the Science and Technology Innovation Program of Hunan Province(No.2023RC3188)the financial support of the Science and Technology Innovation Program of Hunan Province(No.2022RC1112)the Elite Youth Program by the Department of Education of Hunan Province(No.21B0666)the financial support of the Scientific Research Foundation of Hunan Provincial Education Department(No.24C0380)。
文摘Machine learning methodologies have been extensively leveraged across diverse domains of chemical research,yielding remarkable outcomes,and exhibit substantial potential for impactful future applications within the field of supramolecular chemistry.The recognition of alkali metal ions by crown ethers is one of the most classic and widely applied host-vip interactions in supramolecular chemistry.Due to the numerous factors affecting the host-vip interaction,it remains a great challenge to achieve fast and accurate prediction of the binding constants between crown ethers and alkali metal ions.Herein,we report a highly accurate machine learning model that can effectively predict the binding constants between crown ethers and alkali metal ions,i.e.,CrownBind-IA,with a low RMSE of 0.68 logK units.Moreover,this model proves robust extrapolative capabilities by accurately predicting out-of-sample data.The establishment of CrownBind-IA demonstrates the promising application potentials of data-driven machine learning methods in supramolecular chemistry,and it will substantially reduce the time and expense of experimental trials and characterizations,promote the exploration of the mechanism of host-vip interactions,as well as the rational design of novel functional supramolecular host molecules.
基金supported by the Natural Science Foundation of Inner Mongolia(No.2020MS01023).
文摘The interstellar medium molecule thiocarbonyl thioketen,H_(2)CCS,has several stable isomers and has received considerable attention of as-tronomical observation in recent years.The positions of H,C,and S atoms of three isomers lead to di-verse dipole moments and spectro-scopic constants.The anharmonic force field and spectroscopic con-stants of thiocarbonyl thioketen and its isomers are calculated using MP2,B3LYP,and CCSD(T)methods employing correlation consistent basis sets.Molecule structures,rotational spectroscopic constants,and fundamental frequencies are compared with the available experimental data for thiocarbonyl thioketen.Ro-vibrational interaction constants,anharmonic constants,cubic and quartic force constants are predicted for thiocarbonyl thioketen.In addition,some rotational and vibrational spectroscopic parameters are predict-ed with the same level of theory for thioacetylene,HCCSH,and thiirene,(CH)_(2)S.The predic-tions of these spectroscopic constants are expected to guide the future astronomical observa-tion and high resolution experimental work for C_(2)H_(2)S isomers.
文摘Poly(m-phenylene isophthalamide)(PMIA),a key aromatic polyamide,is widely used for its outstanding mechanical strength,high thermal stability,and excellent insulation properties.However,different applications demand varying dielectric properties,so tailoring its dielectric per-formance is essential.PMIA was first synthesized in this study,followed by introducing pores and developing porous PMIA films and PMIA-based composites with reduced dielectric constants.Porous PMIA films were fabricated using the wet phase inversion process with N,N-dimethylac-etamide(DMAC)solvent and water as the non-solvent.The impact of casting solution composi-tion and coagulation bath temperature on pore structures was analyzed.A film produced with 18%PMIA and 5%LiCl in a 35℃coagulation bath achieved the lowest dielectric constant of 1.76 at 1 Hz,48%lower than the standard PMIA film,which had a tensile strength of 18.5 MPa and an initial degradation temperature of 320℃.
基金Projects(5137550251305466) supported by the National Natural Science Foundation of China+2 种基金Project(2015CX002) supported by the Innovation-driven Plan in Central South University,ChinaProject(2013CB035801) supported by the National Basic Research Program of ChinaProject(2015NGQ001) supported by Key Laboratory of Efficient&Clean Energy Utilization,College of Hunan Province,China
文摘Effects of initial δ phase（Ni_3Nb） on the hot tensile deformation behaviors and material constants of a Ni-based superalloy were investigated over wide ranges of strain rate and deformation temperature. It is found that the true stress-true strain curves exhibit peak stress at a small strain, and the peak stress increases with the increase of initial δ phase. After the peak stress, initial δ phase promotes the dynamic softening behaviors, resulting in the decreased flow stress. An improved Arrhenius constitutive model is proposed to consider the synthetical effects of initial δ phase, deformation temperature, strain rate, and strain on hot deformation behaviors. In the improved model, material constants are expressed as the functions of the content of initial δ phase and strain. A good agreement between the predicted and measured results indicates that the improved Arrhenius constitutive model can well describe hot deformation behaviors of the studied Ni-based superalloy.
基金supported by the National Natural Science Foundation of China(Grant No.11134011)
文摘The positive and negative difference of deep and shallow resisitivity in formation without invasion is caused mainly by the fixed two tool constants from numerical simulations. A dynamic calibration method for tool constants is proposed based on the effects of the mud and formation resisitivity ratio on the two constants calculated using the finite element method （FEM）. Finally, four specific examples are given to validate the dynamic calibration method. It is an automatic borehole correction method and can give more accurate formation resistivity. The method is useful for dual laterolog logging.
基金The National Natural Science Foundation of China(No.51278299,50878128)
文摘This paper presents an experimental study to determine the tensile properties of the envelope fabric Uretek3216L under biaxial cyclic loading.First the biaxial cyclic tests were carefully carried out on the envelope material to obtain the stress-strain data and the corresponding nonlinearity and orthotropy of the material were analyzed. Then for some determination options with different stress ratios the least squares method minimizing the strain terms was used to calculate the elastic constants from the experimental data.Finally the influences of the determination options with different stress ratios and the reciprocal relationship on the elastic constants were discussed.Results show that the orthotropy of the envelope material can be attributed to the unbalanced crimp of their constitutive yarns in warp and weft directions and the elastic constants vary noticeably with the determination options as well as the normalized stress ratios.In real design practice it is more reasonable to use constants determined for specific stress states in particular stress ratios depending on the project＆#39;s needs.Also calculating the structures with two limitative sets of elastic constants instead of using only one set is recommendable in light of the great variety of the constant＆#39;s values.
基金Acknowledgment： This work was supported by the National Natural Science Foundation of China （No.20673107 and No.20873133）, the National Basic Research Program of China （No.2007CB815203 and No.2010CB923302）, the Chinese Academy of Sciences （No.KJCX2-YW-N24）, and the Scientific Research Foundation for the Returned Overseas Chinese Scholars, Ministry of Education of China.
文摘Based on previous laser-induced fluorescence excitation spectroscopy work, the vibrational constants of neutral FeS in the X5 △ electronic state were obtained by directly mapping the ground-state vibrational levels up to v＂=3 using conventional laser-induced dispersed fluorescence spectroscopy. The vibrational frequency of FeS（X5 △） （518±5 cm-1） agrees well with that reported in a recent PES measurement （520±30 cm-1） [J. Phys. Chem. A 107, 2821 （2003）] which is the only one prior experimental vibrational frequency value for the 5 △ state of FeS. Careful comparisons of our experimental results and those documented in the literature （mainly from theoretical predictions） suggest that the ground state of FeS is 5 △ state.
文摘The cadmium（Ⅱ）-glycine system was studied by the two experimental techniques, ion sensitive electrode （ISE） and differential pulse polarography （DPP）, and the experimental data obtained were used by a unified mathematical treatment to calculate the complex stability constants. The combination of the two techniques is of many advantages as ISE can be performed at low [LT]：[MT] ratios and significantly higher [MT], whereas DPP could be used well at large [LT]：[MT] ratios and much smaller [MT]. This makes it possible to study a metal-ligand system in a relatively broader range of experimental conditions that, in turn, provides more information about the metakligand system of interest. Applying the unified mathematical treatment to the cadmium-glycine system, two new complexes MHL and ML2（OH） as well as three complexes ML, ML2 and ML3, reported in literatures, could be modeled and all their stability constants have been refined.
文摘By double beam and double wave interferomatric (DDI) method, the optical constants of thin films, i.e. refractive index, extinction coefficient and thickness may be determined in infrared (3.39 μm) and in visible (0.633 μm) wavelengths in the same optical path with a tunable double wave He Ne laser designed by ourselves. The measuring principle and the device are describod.
基金Supported by National Natural Science Foundation of China(No.81770905)
文摘AIM: To evaluate the effect of different lens constant optimization methods on the accuracy of intraocular lens(IOL) power calculation formulas for highly myopic eyes.METHODS: This study comprised 108 eyes of 94 consecutive patients with axial length(AL) over 26 mm undergoing phacoemulsification and implantation of a Rayner(Hove, UK) 920H IOL. Formulas were evaluated using the following lens constants: manufacturer’s lens constant, User Group for Laser Interference Biometry(ULIB) constant, and optimized constant for long eyes. Results were compared with Barrett Universal II formula, original Wang-Koch AL adjustment method, and modified Wang-Koch AL adjustment method. The outcomes assessed were mean absolute error(MAE) and percentage of eyes with IOL prediction errors within ±0.25, ±0.50, and ±1.0 diopter(D). The nonparametric method, Friedman test, was used to compare MAE performance among constants.RESULTS: Optimized constants could significantly reduce the MAE of SRK/T, Hoffer Q, and Holladay 1 formulas compared with manufacturer’s lens constant, whereas the percentage of eyes with IOL prediction errors within ±0.25, ±0.50, and ±1.0 D had no statistically significant differences. Optimized lens constant for long eyes alone showed non-significant refractive advantages over the ULIB constant. Barrett Universal II formula and formulas with AL adjustment showed significantly higher accuracy in highly myopic eyes(P<0.001). CONCLUSION: Lens constant optimization for the subset of long eyes reduces the refractive error only to a limited extent for highly myopic eyes.
文摘The binding of Tb 3+ to chicken apoovotransferrin was studied by monitoring the fluorescent intensity of Tb 3+ at 549 nm. The conditional equilibrium constants for the complexation of Tb 3+ by chicken apoovotransferrin in 0 1 mol/L hepes, at pH 7 4 and room temperature were measured. The successive macroscopic binding constants are lg K 1=9 08±0 12 and lg K 2=7 36±0 22. The molar fluorescence enhancement of Tb 3+ apoovotransferrin complex is (2 06±0 14)×10 4 mol -1 ·L. The fluorescence quenching experiment and the titration of N terminal monoferric ovotransferrin showed that Tb 3+ has a preference for being bound to the N terminal binding site of apoovotransferrin.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11074232,10874160,and 21002097)the National Basic Research Program of China(Grant Nos.2011CB932801 and 2012CB933702)
文摘Thin oxidized copper films in various thickness values are deposited onto quartz glass substrates by electron beam evaporation. The ellipsometry parameters and transmittance in a wavelength range of 300 nm-1000 nm are collected by a spectroscopic ellipsometer and a spectrophotometer respectively. The effective thickness and optical constants, i.e., refractive index n and extinction coefficient k, are accurately determined by using newly developed ellipsometry combined with transmittance iteration method. It is found that the effective thickness determined by this method is close to the physical thickness and has obvious difference from the mass thickness for very thin film due to variable density of film. Furthermore, the thickness dependence of optical constants of thin oxidized Cu films is analyzed.
基金Project supported by the National Natural Science Foundation of China （Grant No 10574039）, the Henan Innovation for University Prominent Research Talents （Grant No 2006KYCX002） and the Natural Science Foundation of Henan Province （Grant Nos 2006140008 and 2007140015）.
文摘The density functional theory （B3LYP, B3P86） and the quadratic configuration-interaction method including single and double substitutions （QCISD（T）, QCISD） presented in Gaussian03 program package are employed to calculate the equilibrium internuclear distance Re, the dissociation energy De and the harmonic frequency We for the XIEg＋ state of sodium dimer in a number of basis sets. The conclusion is gained that the best Re, De and We results can be attained at the QCISD/6-311G（3df,3pd） level of theory. The potential energy curve at this level of theory for this state is obtained over a wide internuclear separation range from 0.16 to 2.0 nm and is fitted to the analytic Murrell-Sorbie function. The spectroscopic parameters De, DO, Re, ωe, ωe Xe, αe and Be are calculated to be 0.7219 eV, 0.7135 eV, 0.31813 nm, 151.63 cm^-1, 0.7288 cm^-1, 0.000729 cm^-1 and 0.1449 cm^-1, respectively, which are in good agreement with the measurements. With the potential obtained at the QCISD/6-311G（3df,3pd） level of theory, a total of 63 vibrational states is found when J = 0 by solving the radial SchrSdinger equation of nuclear motion. The vibrational level, corresponding classical turning point and inertial rotation constant are computed for each vibrational state. The centrifugal distortion constants （Dr Hv, Lv, Mv, Nv and Ov） are reported for the first time for the first 31 vibrational states when J = 0.
文摘Ab initio VB calculations were used to determine the accurate spectroscopic parameters of the ground states of LiF and NaF. A set of potential energy curves corresponding to the ground states including ionic and covalent interactions, pure ionic interaction and covalent interaction were generated using the VBSCF method. Curve crossing in the dissociation processes of LiF and NaF was discussed. The optimized VB wave functions suggest that LiF and NaF are of high ionicity, and their ionic weights are 86 2% and 94 6%, respectively. NaF has a higher ionicity. The main difference between atom F and ion F - and the effect of the proper description of this difference on dissociation energies were investigated.
基金Projected supported by the National Natural Science Foundation of China(Nos.11502123 and11262012)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(No.2015JQ01)
文摘A three-phase confocal elliptical cylinder model is proposed to analyze micromechanics of one-dimensional hexagonal piezoelectric quasicrystal （PQC） compos- ites. Exact solutions of the phonon, phason, and electric fields are obtained by using the conformal mapping combined with the Laurent expansion technique when the model is subject to far-field anti-plane mechanical and in-plane electric loadings. The effective elec- troelastic constants of several different composites made up of PQC, quasicrystal （QC）, and piezoelectric （PE） materials are predicted by the generalized self-consistent method. Numerical examples are conducted to show the effects of the volume fraction and the cross-sectional shape of inclusion （or fiber） on the effective electroelastic constants of these composites. Compared with other micromechanical methods, the generalized self- consistent and Mori-Tanaka methods can predict the effective electroelastic constants of the composites consistently.
基金Project supported by the National Natural Science Foundation of China(Nos.11872186 and11272126)the Fundamental Research Funds for the Central Universities(No.HUST:2016JCTD114)
文摘The definitions of the third-order elastic,piezoelectric,and dielectric constants and the properties of the associated tensors are discussed.Based on the energy conservation and coordinate transformation,the relations among the third-order constants are obtained.Furthermore,the relations among the third-order elastic,piezoelectric,and dielectric constants of the seven crystal systems and isotropic materials are listed in detail.These third-order constants relations play an important role in solving nonlinear problems of elastic and piezoelectric materials.It is further found that all third-order piezoelectric constants are 0 for 15 kinds of point groups,while all third-order dielectric constants are 0 for 16 kinds of point groups as well as isotropic material.The reason is that some of the point groups are centrally symmetric,and the other point groups are high symmetry.These results provide the foundation to measure these constants,to choose material,and to research nonlinear problems.Moreover,these results are helpful not only for the study of nonlinear elastic and piezoelectric problems,but also for the research on flexoelectric effects and size effects.
基金Part of the calculations in this work was performed ona Shenteng 6800 supercomputer at CNIC, China.
文摘To investigate the origin of the strong dependence of martensitic transformation temperature on composition, the elastic properties of high temperature B2 phases of both NiTi and NiAI were calculated by a first-principle method, the exact-muffin orbital method within coherent potential approximation. In the composition range of 50-56 at. pct Ni of NiTi and 60-70 at. pct Ni of NiAI in which martensitic transformation occurs, non-basalplane shear modulus c44 increases with increasing Ni content, while basal-plane shear modulus c＇ decreases. In the above composition ranges however the transformation temperature of NiAI increases with increasing Ni content while that of NiTi decreases from experimental observation. The softening of c＇ is experimentally observed only in NiAI, and the decrease of c＇ with increasing Ni content is responsible for the increase of transformation temperature. The result of the present work demonstrates that, besides c＇, c44 also influences the martensitic transformation of NiTi and plays quite important a role.
基金the Robert A. Welch Foundation (A-0259) in the U.S and China Scholarship Council is gratefully acknowledged.
文摘The protonation constants of a new dinucleating 24-membered hexaazadiphenol macrocyclic ligand, BDBPH, were determined by potentiometric measurement at 25.0 degreesC and mu = 0.100 mol.L-1 (KCl). The species distributions of the deprotonated and protonated compounds in the pH range from 2 to 12 aqueous solutions were also described.
基金Project supported by the Jiangsu Provincial Natural Science Foundation,China(Grant Nos.BK20170800 and BK20160794)the National Natural Science Foundation of China(Grant No.51606095)
文摘The angular light-scattering measurement（ALSM） method combined with an improved artificial bee colony algorithm is introduced to determine aerosol optical constants and aerosol size distribution（ASD） simultaneously. Meanwhile, an optimized selection principle of the ALSM signals based on the sensitivity analysis and principle component analysis（PCA）is proposed to improve the accuracy of the retrieval results. The sensitivity analysis of the ALSM signals to the optical constants or characteristic parameters in the ASD is studied first to find the optimized selection region of measurement angles. Then, the PCA is adopted to select the optimized measurement angles within the optimized selection region obtained by sensitivity analysis. The investigation reveals that, compared with random selection measurement angles, the optimized selection measurement angles can provide more useful measurement information to ensure the retrieval accuracy. Finally,the aerosol optical constants and the ASDs are reconstructed simultaneously. The results show that the retrieval accuracy of refractive indices is better than that of absorption indices, while the characteristic parameters in ASDs have similar retrieval accuracy. Moreover, the retrieval accuracy in studying L-N distribution is a little better than that in studying Gamma distribution for the difference of corresponding correlation coefficient matrixes of the ALSM signals. All the results confirm that the proposed technique is an effective and reliable technique in estimating the aerosol optical constants and ASD simultaneously.
文摘The Al film reflectors can yield a high-reflectance over a broad wavelength region, and have been widely used in the spacecraft optical instruments for high quality optical applications. Under the irradiation of charged particles in the Earth radiation belt, the reflectors could be deteriorated. In order to reveal the deterioration mechanism, the change in optical constants of Al film reflector induced by proton radiation with 60 keV was studied in an environment of vacuum with heat sink. Experimental results showed that when the radiation damage primarily occurs in the Al reflecting film, the extinction coefficient k will gradually decrease with increasing radiation fluence, which results in the decrease of the energies of reflective light. Therefore, the proton radiation induced an obvious degradation of spectral reflectance in the wavelength region from 200 to 800nm on the Al film reflector.
