A three-dimensional elasto-plastic finite element analysis of pre-twist process for a torsional axis made of 45GrNiMoVA steel, was carried out using a commercial finite element analysis code, MSC MARC 2001. The result...A three-dimensional elasto-plastic finite element analysis of pre-twist process for a torsional axis made of 45GrNiMoVA steel, was carried out using a commercial finite element analysis code, MSC MARC 2001. The results show that the critical pre-twist strain angle is 0.027 rad and the maximum elastic shear stress after pre-twist is 1694MPa for the torsional axis.展开更多
This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional sh...This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional shear apparatus was utilized to conduct tests on remolded samples under both normal and frozen conditions to investigate the mechanical properties and deformation behavior of loess under complex stress conditions. The results indicate significant differences in the internal changes of soil particles, unfrozen water, and relative positions in soil samples under normal and frozen conditions, leading to noticeable variations in strength and strain development.In frozen state, loess experiences primarily compressive failure with a slow growth of cracks, while at normal temperature, it predominantly exhibits shear failure. With the increase in the principal stress angle, the deformation patterns of the soil samples under different conditions become essentially consistent, gradually transitioning from compression to extension, accompanied by a reduction in axial strength. The gradual increase in the principal stress axis angle(α) reduces the strength of the generalized shear stress and shear strain curves.Under an increasing α, frozen soil exhibits strain-hardening characteristics, with the maximum shear strength occurring at α = 45°. The intermediate principal stress coefficient(b) also significantly impacts the strength of frozen soil, with an increasing b resulting in a gradual decrease in generalized shear stress strength. This study provides a reference for comprehensively exploring the mechanical properties of soil under traffic load and a reliable theoretical basis for the design and maintenance of roadbeds.展开更多
Let 0<γ<π be a fixed pythagorean angle. We study the abelian group Hr of primitive integral triangles (a,b,c) for which the angle opposite side c is γ. Addition in Hr is defined by adding the angles β opposi...Let 0<γ<π be a fixed pythagorean angle. We study the abelian group Hr of primitive integral triangles (a,b,c) for which the angle opposite side c is γ. Addition in Hr is defined by adding the angles β opposite side b and modding out by π-γ. The only Hr for which the structure is known is Hπ/2, which is free abelian. We prove that for generalγ, Hr has an element of order two iff 2(1- cosγ) is a rational square, and it has elements of order three iff the cubic (2cosγ)x3-3x2+1=0 has a rational solution 0<x<1. This shows that the set of values ofγ for which Hr has two-torsion is dense in [0, π], and similarly for three-torsion. We also show that there is at most one copy of either Z2 or Z3 in Hr. Finally, we give some examples of higher order torsion elements in Hr.展开更多
Constructing blue thermally activated delayedfluorescence materials for high-performance organic light-emitting diodes(OLEDs)remains challenging due to the intrinsically strong intramolecular charge transfer nature of...Constructing blue thermally activated delayedfluorescence materials for high-performance organic light-emitting diodes(OLEDs)remains challenging due to the intrinsically strong intramolecular charge transfer nature of the nearly orthogonal connection of electron donor(D)and acceptor(A),which results in long-wavelength emission.Herein,an effective delayed-fluorescence design strategy of modulating D–A torsion angles is proposed and efficient sky-blue,pure-blue,and deep-blue delayed-fluorescence molecules consisting of a xanthenone acceptor and carbazole-based donors are created by decreasing the torsion angles.They exhibit strong delayed fluorescence with high photoluminescence quantum yields of 85–94%in doped films,and their delayed-fluorescence lifetimes are elongated from 1.0 to 27.6μs as the torsion angles decrease.These molecules can function as excellent emitters in OLEDs,providing efficient electroluminescence peaking at 442 nm(CIEx,y=0.15,0.08),462 nm(CIEx,y=0.15,0.18),and 482 nm(CIEx,y=0.17,0.30)with state-of-the-art external quantum efficiencies of up to 22.2%,33.7%,and 32.1%,respectively,demonstrating the proposed molecular design for efficient blue delayed-fluorescence molecules is successful and promising.展开更多
AIM:To study the change of torsion in both eyes after unilateral inferior oblique(IO)weakening on children with congenital superior oblique palsy(SOP).METHODS:This retrospective study enrolled all patients diagnosed w...AIM:To study the change of torsion in both eyes after unilateral inferior oblique(IO)weakening on children with congenital superior oblique palsy(SOP).METHODS:This retrospective study enrolled all patients diagnosed with unilateral congenital superior oblique palsy(UCSOP)accompanied by inferior oblique overaction(IOOA).A total of 120 eyes of 60 patients were divided into group 1(more extorted paretic eye)and group 2(more extorted nonparetic eye).The degree of fundus torsion was evaluated before and 1 mo after the IO weakening procedure.The torsion of the fundus was recorded by measuring the diskfoveal angle(DFA)using fundus photography.RESULTS:Group 1 included 26 cases and group 2 included 34 cases,thus the rate of extorsion was insignificantly higher in the nonparetic eye(P=0.10).The preoperative DFA in the paretic and nonparetic eyes was 13.21±5.95,7.97±4.25 in group 1,and 4.65±3.79,13.16±5.35 in group 2(both P<0.001).The postoperative DFA in the paretic and nonparetic eyes was 8.57±4.87,7.32±4.27 in group 1(P=0.24),and 3.85±6.00 and 9.94±5.45 in group 2(P<0.001).The amount of postoperative reduction of the DFA in the paretic and nonparetic eyes was 4.64±3.90,0.65±0.76 in group 1(P=0.002),and 0.80±0.81,3.21±5.50 in group 2(P=0.01).The difference in the amount of reduction of DFA in the more extorted eye in group 1(paretic eye)vs group 2(nonparetic eye)was insignificant(P=0.30).CONCLUSION:Excyclotorsion in the nonparetic eye has a similar probability in the paretic eye in UCSOP children,and weakening of the ipsilateral IO has a more obvious effect on the decrement of extorsion in the more extorted eye regardless of which eye is paretic.展开更多
BACKGROUND： Poly （glycolide-co-L-lactide） （PGLA） braided regeneration conduits have been shown to be biocompatible for the repair of damaged nerve. Mechanical properties, such as radial compression and torsion, g...BACKGROUND： Poly （glycolide-co-L-lactide） （PGLA） braided regeneration conduits have been shown to be biocompatible for the repair of damaged nerve. Mechanical properties, such as radial compression and torsion, greatly influence nerve regeneration and functional recovery. OBJECTIVE： To observe the influence of conduit parameters and coating methods on torsion properties in an in vitro-degradation environment and at normal temperature. DESIGN, TIME AND SE＇I-FING： An in vitro, comparative study using repeated measures was performed at the College of Textiles, Donghua University, China from January 2005 to December 2007. MATERIALS： PGLA fiber and yarn （Shanghai Bio-TianQing, China）, as well as torsion property testing instrument （LaiZhou Electronic Instrument, China）, were used in the present study. METHODS： A total of 16 types of conduits were constructed according to braiding structures （regular/triaxial）, angles （50°/55°/60°/65°）nd coating methods （coated/uncoated）. At normal temperature, torsion properties of all conduits were tested at a predefined constant angle of 90°. Coated and uncoated conduits, which were triaxial and 65°, were incubated in a 5% CO2 incubator at 37 ℃ to simulate an in vitro degradation environment, and then torsion properties were tested at 4, 7, 11, 14, 17, 21,24, and 28 days in culture. MAIN OUTCOME MEASURES： Maximal torsion strength and torsion strength-torsion angle curve of conduits at normal temperature, as well as torsion strength-torsion angle curve, loss of torsion strength, and change in maximal torsion strength in an in vitro degradation environment. RESULTS： At normal temperature, the torsion properties of the triaxial structure were superior to the regular structure. Coated conduits performed better than uncoated ones, and the larger braiding angles exhibited superior torsion properties （P 〈 0.05）. In the in vitro degradation environment, with degradation time, torsion strength of uncoated conduits was deceased gradually and the loss of torsion strength was increased fast. Torsion strength of coated conduits was increased first and decreased afterwards; the loss of torsion strength was decreased slowly till 14 days; both became identical after 14 days （P 〉 0.05）. CONCLUSION： Torsion properties of coated conduits with a triaxial structure and large braiding angle were superior to uncoated conduits with regular structures and small braiding angles.展开更多
We apply general tensor calculus to arbitrary nonrelativistic classical Lagrangian systems and derive general relationships between the torsion tensor and other quantities associated with the coordinate configuration ...We apply general tensor calculus to arbitrary nonrelativistic classical Lagrangian systems and derive general relationships between the torsion tensor and other quantities associated with the coordinate configuration space, such as the metric, the Christoffel symbols, the Euler-Lagrange equations, the affine connections, and the curvature tensor. Using Euler angle metric spaces as examples of spaces with nonzero torsion, we calculate these quantities for nonrelativistic rigid rotators of arbitrary structure. For free rotations, we show that the Euler-Lagrange equations agree with the manifestly correct Euler equations.展开更多
文摘A three-dimensional elasto-plastic finite element analysis of pre-twist process for a torsional axis made of 45GrNiMoVA steel, was carried out using a commercial finite element analysis code, MSC MARC 2001. The results show that the critical pre-twist strain angle is 0.027 rad and the maximum elastic shear stress after pre-twist is 1694MPa for the torsional axis.
基金This work was supported by the National Natural Science Foundation of China(Nos.42161026&41801046)the Natural Science Foundation of Qinghai Province(No.2023-ZJ-934M)the Youth Research Foundation of Qinghai University(No.2022-QGY-5).
文摘This paper aims to comprehensively analyze the influence of the principal stress angle rotation and intermediate principal stress on loess's strength and deformation characteristics. A hollow cylinder torsional shear apparatus was utilized to conduct tests on remolded samples under both normal and frozen conditions to investigate the mechanical properties and deformation behavior of loess under complex stress conditions. The results indicate significant differences in the internal changes of soil particles, unfrozen water, and relative positions in soil samples under normal and frozen conditions, leading to noticeable variations in strength and strain development.In frozen state, loess experiences primarily compressive failure with a slow growth of cracks, while at normal temperature, it predominantly exhibits shear failure. With the increase in the principal stress angle, the deformation patterns of the soil samples under different conditions become essentially consistent, gradually transitioning from compression to extension, accompanied by a reduction in axial strength. The gradual increase in the principal stress axis angle(α) reduces the strength of the generalized shear stress and shear strain curves.Under an increasing α, frozen soil exhibits strain-hardening characteristics, with the maximum shear strength occurring at α = 45°. The intermediate principal stress coefficient(b) also significantly impacts the strength of frozen soil, with an increasing b resulting in a gradual decrease in generalized shear stress strength. This study provides a reference for comprehensively exploring the mechanical properties of soil under traffic load and a reliable theoretical basis for the design and maintenance of roadbeds.
文摘Let 0<γ<π be a fixed pythagorean angle. We study the abelian group Hr of primitive integral triangles (a,b,c) for which the angle opposite side c is γ. Addition in Hr is defined by adding the angles β opposite side b and modding out by π-γ. The only Hr for which the structure is known is Hπ/2, which is free abelian. We prove that for generalγ, Hr has an element of order two iff 2(1- cosγ) is a rational square, and it has elements of order three iff the cubic (2cosγ)x3-3x2+1=0 has a rational solution 0<x<1. This shows that the set of values ofγ for which Hr has two-torsion is dense in [0, π], and similarly for three-torsion. We also show that there is at most one copy of either Z2 or Z3 in Hr. Finally, we give some examples of higher order torsion elements in Hr.
基金This study is financially supported by the National Natural Science Foundation of China(grant no.21788102)the Natural Science Foundation of Guangdong Province(grant no.2019B030301003)the State Key Lab of Luminescent Materials and Devices,South China University of Technology。
文摘Constructing blue thermally activated delayedfluorescence materials for high-performance organic light-emitting diodes(OLEDs)remains challenging due to the intrinsically strong intramolecular charge transfer nature of the nearly orthogonal connection of electron donor(D)and acceptor(A),which results in long-wavelength emission.Herein,an effective delayed-fluorescence design strategy of modulating D–A torsion angles is proposed and efficient sky-blue,pure-blue,and deep-blue delayed-fluorescence molecules consisting of a xanthenone acceptor and carbazole-based donors are created by decreasing the torsion angles.They exhibit strong delayed fluorescence with high photoluminescence quantum yields of 85–94%in doped films,and their delayed-fluorescence lifetimes are elongated from 1.0 to 27.6μs as the torsion angles decrease.These molecules can function as excellent emitters in OLEDs,providing efficient electroluminescence peaking at 442 nm(CIEx,y=0.15,0.08),462 nm(CIEx,y=0.15,0.18),and 482 nm(CIEx,y=0.17,0.30)with state-of-the-art external quantum efficiencies of up to 22.2%,33.7%,and 32.1%,respectively,demonstrating the proposed molecular design for efficient blue delayed-fluorescence molecules is successful and promising.
文摘AIM:To study the change of torsion in both eyes after unilateral inferior oblique(IO)weakening on children with congenital superior oblique palsy(SOP).METHODS:This retrospective study enrolled all patients diagnosed with unilateral congenital superior oblique palsy(UCSOP)accompanied by inferior oblique overaction(IOOA).A total of 120 eyes of 60 patients were divided into group 1(more extorted paretic eye)and group 2(more extorted nonparetic eye).The degree of fundus torsion was evaluated before and 1 mo after the IO weakening procedure.The torsion of the fundus was recorded by measuring the diskfoveal angle(DFA)using fundus photography.RESULTS:Group 1 included 26 cases and group 2 included 34 cases,thus the rate of extorsion was insignificantly higher in the nonparetic eye(P=0.10).The preoperative DFA in the paretic and nonparetic eyes was 13.21±5.95,7.97±4.25 in group 1,and 4.65±3.79,13.16±5.35 in group 2(both P<0.001).The postoperative DFA in the paretic and nonparetic eyes was 8.57±4.87,7.32±4.27 in group 1(P=0.24),and 3.85±6.00 and 9.94±5.45 in group 2(P<0.001).The amount of postoperative reduction of the DFA in the paretic and nonparetic eyes was 4.64±3.90,0.65±0.76 in group 1(P=0.002),and 0.80±0.81,3.21±5.50 in group 2(P=0.01).The difference in the amount of reduction of DFA in the more extorted eye in group 1(paretic eye)vs group 2(nonparetic eye)was insignificant(P=0.30).CONCLUSION:Excyclotorsion in the nonparetic eye has a similar probability in the paretic eye in UCSOP children,and weakening of the ipsilateral IO has a more obvious effect on the decrement of extorsion in the more extorted eye regardless of which eye is paretic.
文摘BACKGROUND： Poly （glycolide-co-L-lactide） （PGLA） braided regeneration conduits have been shown to be biocompatible for the repair of damaged nerve. Mechanical properties, such as radial compression and torsion, greatly influence nerve regeneration and functional recovery. OBJECTIVE： To observe the influence of conduit parameters and coating methods on torsion properties in an in vitro-degradation environment and at normal temperature. DESIGN, TIME AND SE＇I-FING： An in vitro, comparative study using repeated measures was performed at the College of Textiles, Donghua University, China from January 2005 to December 2007. MATERIALS： PGLA fiber and yarn （Shanghai Bio-TianQing, China）, as well as torsion property testing instrument （LaiZhou Electronic Instrument, China）, were used in the present study. METHODS： A total of 16 types of conduits were constructed according to braiding structures （regular/triaxial）, angles （50°/55°/60°/65°）nd coating methods （coated/uncoated）. At normal temperature, torsion properties of all conduits were tested at a predefined constant angle of 90°. Coated and uncoated conduits, which were triaxial and 65°, were incubated in a 5% CO2 incubator at 37 ℃ to simulate an in vitro degradation environment, and then torsion properties were tested at 4, 7, 11, 14, 17, 21,24, and 28 days in culture. MAIN OUTCOME MEASURES： Maximal torsion strength and torsion strength-torsion angle curve of conduits at normal temperature, as well as torsion strength-torsion angle curve, loss of torsion strength, and change in maximal torsion strength in an in vitro degradation environment. RESULTS： At normal temperature, the torsion properties of the triaxial structure were superior to the regular structure. Coated conduits performed better than uncoated ones, and the larger braiding angles exhibited superior torsion properties （P 〈 0.05）. In the in vitro degradation environment, with degradation time, torsion strength of uncoated conduits was deceased gradually and the loss of torsion strength was increased fast. Torsion strength of coated conduits was increased first and decreased afterwards; the loss of torsion strength was decreased slowly till 14 days; both became identical after 14 days （P 〉 0.05）. CONCLUSION： Torsion properties of coated conduits with a triaxial structure and large braiding angle were superior to uncoated conduits with regular structures and small braiding angles.
文摘We apply general tensor calculus to arbitrary nonrelativistic classical Lagrangian systems and derive general relationships between the torsion tensor and other quantities associated with the coordinate configuration space, such as the metric, the Christoffel symbols, the Euler-Lagrange equations, the affine connections, and the curvature tensor. Using Euler angle metric spaces as examples of spaces with nonzero torsion, we calculate these quantities for nonrelativistic rigid rotators of arbitrary structure. For free rotations, we show that the Euler-Lagrange equations agree with the manifestly correct Euler equations.
