This article demonstrates a novel approach for material nonlinear analysis.This analysis procedure eliminates tedious and lengthy step by step incremental and then iterative procedure adopted classically and gives dir...This article demonstrates a novel approach for material nonlinear analysis.This analysis procedure eliminates tedious and lengthy step by step incremental and then iterative procedure adopted classically and gives direct results in the linear as well as in nonlinear range of the material behavior.Use of elastic moduli is eliminated.Instead,stress and strain functions are used as the material input in the analysis procedure.These stress and strain functions are directly derived from the stress-strain behavior of the material by the method of curve fitting.This way,the whole stress-strain diagram is utilized in the analysis which naturally exposes the response of structure when loading is in nonlinear range of the material behavior.It is found that it is an excellent computational procedure adopted so far for material nonlinear analysis which gives very accurate results,easy to adopt and simple in calculations.The method eliminates all types of linearity assumptions in basic derivations of equations and hence,eliminates all types of possibility of errors in the analysis procedure as well.As it is required to know stress distribution in the structural body by proper modelling and structural idealization,the proposed analysis approach can be regarded as stress-based analysis procedure.Basic problems such as uniaxial problem,beam bending,and torsion problems are solved.It is found that approach is very suitable for solving the problems of fracture mechanics.Energy release rate for plate with center crack and double cantilever beam specimen is also evaluated.The approach solves the fracture problem with relative ease in strength of material style calculations.For all problems,results are compared with the classical displacement-based liner theory.展开更多
Precisely quantifying the strength of the proximal femur and accurately assessing hip fracture risk would enable those at high risk to be identified so that preventive interventions could be taken.Development of bette...Precisely quantifying the strength of the proximal femur and accurately assessing hip fracture risk would enable those at high risk to be identified so that preventive interventions could be taken.Development of better measures of femoral strength using the clinically展开更多
Ca 4YO(BO 3) 3(YCOB) which possesses good NLO properties and chemical stability,is an excellent candidate for frequency conversion crystals to produce green and blue light (SHG and THG of Nd∶YAG laser).In this paper,...Ca 4YO(BO 3) 3(YCOB) which possesses good NLO properties and chemical stability,is an excellent candidate for frequency conversion crystals to produce green and blue light (SHG and THG of Nd∶YAG laser).In this paper,preparation of the feed material and the vertical Bridgman growth condition for YCOB crystal is reported for the first time to our knowledge. YCOB crystals have been grown from the feed materials composed of Y 2O 3(4N),CaCO 3/CaO (A.R.) and H 3BO 3/B 2O 3(4N)by vertical Bridgman method.Since Ca 4YO(BO 3) 3 melts congruently,the feed material should be prepared in the stoichiometric composition.The evaporation of B 2O 3 at high temperature and the hygroscopicity of CaO,B 2O 3 and Y 2O 3 were carefully considered.It was showed by experiments that the feed material prepared by directly and thoroughly mixing together stoichiometric amount of Y 2O 3,CaO and B 2O 3 is suitable for the Bridgman growth of YCOB crystal.The melting point of YCOB crystal is 1510℃,and Pt crucible less than 1.0mm thick was chosen.The temperature of the furnace was controlled from 1560℃ to 1650℃.Owing to the extremely high melting points of both Y 2O 3 and CaO,the feed material had been heated at the above temperature for more than 10 hours before growth so that it melts thoroughly.The growth rate of 0.2-0.6mm/h and the temperature gradient near the solid-liquid interface of 40-60°C/cm were chosen.The Crack free and transparent YCOB crystals with 25mm in diameter and 50mm long have been grown in near sealed Pt crucibles under the above growth condition,which suggests that the vertical Bridgman method is suitable for the growth of YCOB crystal.展开更多
Two alkali-metal sulfamates nonlinear optical(NLO)crystals,Li(NH_(2)SO_(3))and Na(NH_(2)SO_(3)),have been obtained through the facile evaporation method.Li(NH_(2)SO_(3))crystallizes in the polar space group Pca2_(1)(N...Two alkali-metal sulfamates nonlinear optical(NLO)crystals,Li(NH_(2)SO_(3))and Na(NH_(2)SO_(3)),have been obtained through the facile evaporation method.Li(NH_(2)SO_(3))crystallizes in the polar space group Pca2_(1)(No.29).The structure of Li(NH_(2)SO_(3))can be described as a 3D network formed by[LiO_(4)]^(7-)polyhedral connecting with NH_(2)SO_(3)^(-)tetrahedra through corner-sharing.Na(NH_(2)SO_(3))crystallizes in the polar space group P2_(1)2_(1)2_(1)(No.19).The structure of Na(NH_(2)SO_(3))can be described as a 3D network formed by distorted[NaO_(6)]^(11-)octahedral connecting with NH_(2)SO_(3)^(-)tetrahedra through corner-sharing.The UV-Vis-near-infrared spectra demonstrate that Li(NH_(2)SO_(3))and Na(NH_(2)SO_(3))possessed large optical band gaps of 5.25 and 4.81 eV,respectively.Powder second-harmonic generation(SHG)measurements demonstrate that the SHG intensity of Li(NH_(2)SO_(3))and Na(NH_(2)SO_(3))were 0.32 times and 0.31 times that of KH_(2)PO_(4),respectively.First-principles calculations confirm the nonlinear optical performance mainly derived from the synergistic effect of amino sulfonate anions and alkali metal oxide anionic polyhedra.CCDC:2339109,Li(NH_(2)SO_(3));2339110,Na(NH_(2)SO_(3)).展开更多
文摘This article demonstrates a novel approach for material nonlinear analysis.This analysis procedure eliminates tedious and lengthy step by step incremental and then iterative procedure adopted classically and gives direct results in the linear as well as in nonlinear range of the material behavior.Use of elastic moduli is eliminated.Instead,stress and strain functions are used as the material input in the analysis procedure.These stress and strain functions are directly derived from the stress-strain behavior of the material by the method of curve fitting.This way,the whole stress-strain diagram is utilized in the analysis which naturally exposes the response of structure when loading is in nonlinear range of the material behavior.It is found that it is an excellent computational procedure adopted so far for material nonlinear analysis which gives very accurate results,easy to adopt and simple in calculations.The method eliminates all types of linearity assumptions in basic derivations of equations and hence,eliminates all types of possibility of errors in the analysis procedure as well.As it is required to know stress distribution in the structural body by proper modelling and structural idealization,the proposed analysis approach can be regarded as stress-based analysis procedure.Basic problems such as uniaxial problem,beam bending,and torsion problems are solved.It is found that approach is very suitable for solving the problems of fracture mechanics.Energy release rate for plate with center crack and double cantilever beam specimen is also evaluated.The approach solves the fracture problem with relative ease in strength of material style calculations.For all problems,results are compared with the classical displacement-based liner theory.
基金supported by The HongKong Polytechnic University Research Grants(No.1-BB81)grants from National Natural Science Foundation of China,Nos.10872078 and 10832012
文摘Precisely quantifying the strength of the proximal femur and accurately assessing hip fracture risk would enable those at high risk to be identified so that preventive interventions could be taken.Development of better measures of femoral strength using the clinically
文摘Ca 4YO(BO 3) 3(YCOB) which possesses good NLO properties and chemical stability,is an excellent candidate for frequency conversion crystals to produce green and blue light (SHG and THG of Nd∶YAG laser).In this paper,preparation of the feed material and the vertical Bridgman growth condition for YCOB crystal is reported for the first time to our knowledge. YCOB crystals have been grown from the feed materials composed of Y 2O 3(4N),CaCO 3/CaO (A.R.) and H 3BO 3/B 2O 3(4N)by vertical Bridgman method.Since Ca 4YO(BO 3) 3 melts congruently,the feed material should be prepared in the stoichiometric composition.The evaporation of B 2O 3 at high temperature and the hygroscopicity of CaO,B 2O 3 and Y 2O 3 were carefully considered.It was showed by experiments that the feed material prepared by directly and thoroughly mixing together stoichiometric amount of Y 2O 3,CaO and B 2O 3 is suitable for the Bridgman growth of YCOB crystal.The melting point of YCOB crystal is 1510℃,and Pt crucible less than 1.0mm thick was chosen.The temperature of the furnace was controlled from 1560℃ to 1650℃.Owing to the extremely high melting points of both Y 2O 3 and CaO,the feed material had been heated at the above temperature for more than 10 hours before growth so that it melts thoroughly.The growth rate of 0.2-0.6mm/h and the temperature gradient near the solid-liquid interface of 40-60°C/cm were chosen.The Crack free and transparent YCOB crystals with 25mm in diameter and 50mm long have been grown in near sealed Pt crucibles under the above growth condition,which suggests that the vertical Bridgman method is suitable for the growth of YCOB crystal.
文摘Two alkali-metal sulfamates nonlinear optical(NLO)crystals,Li(NH_(2)SO_(3))and Na(NH_(2)SO_(3)),have been obtained through the facile evaporation method.Li(NH_(2)SO_(3))crystallizes in the polar space group Pca2_(1)(No.29).The structure of Li(NH_(2)SO_(3))can be described as a 3D network formed by[LiO_(4)]^(7-)polyhedral connecting with NH_(2)SO_(3)^(-)tetrahedra through corner-sharing.Na(NH_(2)SO_(3))crystallizes in the polar space group P2_(1)2_(1)2_(1)(No.19).The structure of Na(NH_(2)SO_(3))can be described as a 3D network formed by distorted[NaO_(6)]^(11-)octahedral connecting with NH_(2)SO_(3)^(-)tetrahedra through corner-sharing.The UV-Vis-near-infrared spectra demonstrate that Li(NH_(2)SO_(3))and Na(NH_(2)SO_(3))possessed large optical band gaps of 5.25 and 4.81 eV,respectively.Powder second-harmonic generation(SHG)measurements demonstrate that the SHG intensity of Li(NH_(2)SO_(3))and Na(NH_(2)SO_(3))were 0.32 times and 0.31 times that of KH_(2)PO_(4),respectively.First-principles calculations confirm the nonlinear optical performance mainly derived from the synergistic effect of amino sulfonate anions and alkali metal oxide anionic polyhedra.CCDC:2339109,Li(NH_(2)SO_(3));2339110,Na(NH_(2)SO_(3)).
