Bionic X-shaped vibration isolators have been widely employed in aerospace and other industrial fields,but the stiffness properties of classic X-shaped structures limit the vibration isolation ability for low frequenc...Bionic X-shaped vibration isolators have been widely employed in aerospace and other industrial fields,but the stiffness properties of classic X-shaped structures limit the vibration isolation ability for low frequencies.An innovative bionic quasi-zero stiffness(QZS)vibration isolator(BQZSVI),which can broaden the QZS range of a classic X-shaped isolator and can bring it closer to the equilibrium position,is proposed.The BQZSVI consists of an X-shaped structure as the bone fabric of lower limbs and a nonlinear magnetic loop device simulating the leg muscle.Based on static calculation,the stiffness characteristic of the structure is confirmed.The governing equations of motion of the BQZSVI structure are established in the framework of the Lagrange equation,and the harmonic balance method(HBM)is adopted to obtain the transmissibility responses.The results show that the BQZSVI can provide a more accessible and broader range of QZS.In the dynamic manifestation,the introduction of the BQZSVI can reduce the amplitude of a classic X-shaped vibration isolator by 65.7%,and bring down the initial vibration isolation frequency from 7.43 Hz to 2.39 Hz.In addition,a BQZSVI prototype is designed and fabricated,and the exactitude of the theoretical analysis method is proven by means of experiments.展开更多
A novel X-shaped variable stiffness vibration isolator(X-VSVI)is proposed.The Runge-Kutta method,harmonic balance method,and wavelet transform spectra are introduced to evaluate the performance of the X-VSVI under var...A novel X-shaped variable stiffness vibration isolator(X-VSVI)is proposed.The Runge-Kutta method,harmonic balance method,and wavelet transform spectra are introduced to evaluate the performance of the X-VSVI under various excitations.The layer number,the installation angle of the X-shaped structure,the stiffness,and the active control parameters are systematically analyzed.In addition,a prototype of the X-VSVI is manufactured,and vibration tests are carried out.The results show that the proposed X-VSVI has a superior adaptability to that of a traditional X-shaped mechanism,and shows excellent vibration isolation performance in response to different amplitudes and forms of excitations.Moreover,the vibration isolation efficiency of the device can be improved by appropriate adjustment of parameters.展开更多
Existing quasi-zero stiffness(QZS)isolators are reviewed.In terms of their advantages,a novel X-shape QZS isolator combined with the cam-roller-spring mechanism(CRSM)is proposed.Different from the existing X-shape iso...Existing quasi-zero stiffness(QZS)isolators are reviewed.In terms of their advantages,a novel X-shape QZS isolator combined with the cam-roller-spring mechanism(CRSM)is proposed.Different from the existing X-shape isolators,oblique springs are used to enhance the negative stiffness of the system.Meanwhile,the CRSM is used to eliminate the gravity of the loading mass,while the X-shape structure leaves its static position.The existing QZS isolators are demonstrated and classified according to their nonlinearity mechanisms and classical shapes.It is shown that the oblique spring can realize negative stiffness based on the simplest mechanism.The X-shape has a strong capacity of loading mass,while the CRSM can achieve a designed restoring force at any position.The proposed isolator combines all these advantages together.Based on the harmonic balance method(HBM)and the simulation,the displacement transmissibilities of the proposed isolator,the X-shape isolators just with oblique springs,and the X-shape isolators in the traditional form are studied.The results show that the proposed isolator has the lowest beginning isolation frequency and the smallest maximum displacement transmissibility.However,it still has some disadvantages similar to the existing QZS isolators.This means that its parameters should be designed carefully so as to avoid becoming a bistable system,in which there are two potential wells in the potential energy curve and thus the isolation performance will be worsened.展开更多
To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement,two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial co...To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement,two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial compression load and low reversed cyclic loading,which imitated low to moderate earthquake force.The seismic behavior of specially shaped column joints with X-shaped reinforcement in terms of bearing capacity,displacement,ductility,hysteretic curve,stiffness degradation and energy dissipation was studied and compared to that without Xshaped reinforcement in joint core region.With the damage estimation model,the accumulated damage was analyzed.The shearing capacity formula of specially shaped column joints reinforced by X-shaped reinforcement was proposed with a simple form.The test results show that X-shaped reinforcement is an effective measure for improving the seismic behavior of specially shaped column joints including deformation behavior,ductility and hysteretic characteristic.All specimens were damaged with gradual stiffness degeneration.In addition,X-shaped reinforcement in the joint core region is an effective way to lighten the degree of cumulated damage.The good seismic performance obtained from the specially shaped column joint with X-shaped reinforcement can be used in engineering applications.The test value is higher than the calculated value,which indicates that the formula is safe for the design of specially shaped column joints.展开更多
The transitions and morphology of a series of main-chain liquid crystalline polymer with X-shaped mesogens were studied by means of DSC,SALS and polarizing microscopy techniques. Aneven-odd effect was observed for sam...The transitions and morphology of a series of main-chain liquid crystalline polymer with X-shaped mesogens were studied by means of DSC,SALS and polarizing microscopy techniques. Aneven-odd effect was observed for samples with different size of the substituents on the mesogenends. The isotropization process was similar to that of main-chain polymers with rod-likemesogens. No crystallization was detected for specimens cooling down from their isotropic meltstate. However two of the samples may crystallize in cooling process directly from the liquidcrystalline state.展开更多
A novel series of main chain liquid crystalline copolyesters with X-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 was prepared via solution conde...A novel series of main chain liquid crystalline copolyesters with X-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4＇-（a;arhexanedioyloxy） dibenzoyl dichloride （MI）, 2,5-bis（p-octyloxybenzoyloxy） hydro-quinone （M2） and cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 （M3）. Monomer MI was synthesized by esterification and substitution of adipoyl chloride with p-hydroxybenzoic acid, monomer M2 was synthesized by esterfication and reduction reaction of 2,5-dihydroxybenzoquinone and p-octanoxybenzoyl chloride and monomer M3 was synthesized by diazotization and coupling reaction of cis-diaminodibenzo-18-crown-6 with phenol. The molecular weights of copolyesters are not high, and the intrinsic viscosity [η] of copolyesters ranges from 0.25-0.35. The monomers＇ structures were identified by using elemental analysis, IR, UV, ^1H-NMR, MS, etc. All the copolyesters are yellowish powders and insoluble in THF and CHC13 at room temperature except cPg. The properties of copolyesters were investigated by using GPC, [η] , DSC, TG, WAXD and POM. It was found that all the copolyesters entered into liquid crystal phase when they were heated to above their melting temperature （Tin）. The typical smectic and nematic phase texture can be observed on POM. Their mesophase transition temperature and thermal stability change regularly with varying the content of cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 unit in the copolyesters.展开更多
A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl di...A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl dichlorides with 2,5-bis(p-octanoxy benzoyloxy)-hydroquinone and diphenol. All of the copolyesters showed thermotropic liquid crystalline behaviors through observations using DSC, polarized microscopy and X-ray diffraction. The melting point (T-m) and the isotropization temperature (T-i) change regularly with varying the content of diphenol unit in the copolymers.展开更多
Musculoskeletal diseases such as neck, shoulder, back and leg pain are ext remely common in clinic. Diseases of the joints of the ext remi ti es, especially sputum, wr ist spr ains, and periarthritis of the shoulders,...Musculoskeletal diseases such as neck, shoulder, back and leg pain are ext remely common in clinic. Diseases of the joints of the ext remi ti es, especially sputum, wr ist spr ains, and periarthritis of the shoulders, and even lumbar disc herniation, use X-shaped balance acupuncture therapy to relieve pain and improve motor function. The method of obtaining acupoints is simple and easy to operate. Many of clinical comparison shows that this therapy is simple to conventional acupuncture and moxibustion in the treatment of local pain and joint diseases. This review concluded the advantaged about the X-shaped balance acupuncture therapy and it worth to clinical promotion.展开更多
The high-speed railway track-bridge system(HSRTBS)is susceptible to damage under the effects of earthquakes,thus threatening the safety of running trains.To improve the seismic performance of HSRTBS and reduce damage ...The high-speed railway track-bridge system(HSRTBS)is susceptible to damage under the effects of earthquakes,thus threatening the safety of running trains.To improve the seismic performance of HSRTBS and reduce damage to the system,a replaceable X-shaped Energy Dissipating Steel Damper(X-EDSD)is proposed,which contains the energy-dissipating component(EDC)to dissipate the earthquake energy.Cyclic tests were performed to obtain the hysteretic performance of the EDC and X-EDSD,and a test-validated numerical model was developed to conduct parametric analyses.The X-EDSD was simplified as a nonlinear spring element with hysteretic parameters and modeled into the numerical model of the HSRTBS for seismic dynamic analyses.The peak displacements of girder and rail decreased by approximately 48.1%and 47.7%,respectively.The peak deflections of the fasteners,cement asphalt mortar layer and sliding layer were reduced by 70.4%,70.8%,and 86.1%,respectively.A comprehensive consideration of the system response control-economic cost ratio coefficient R_(pe)is proposed,and the optimal thickness of 14.94 mm is obtained by applying cubic term coefficient fitting according to 5 groups of steel plate thickness data for the specific case study in this paper.The method can be used for cost-informed X-EDSD-selection for seismic mitigation of HSRTBS.展开更多
Combining with entransy theory, constructal designs of the X-shaped vascular networks(XSVNs) are implemented with fixed total tube volumes of the XSVNs. The entransy dissipation rates(EDRs) of the XSVNs are minimized,...Combining with entransy theory, constructal designs of the X-shaped vascular networks(XSVNs) are implemented with fixed total tube volumes of the XSVNs. The entransy dissipation rates(EDRs) of the XSVNs are minimized, and the optimal constructs of the XSVNs are derived. Comparison of the optimal constructs of the XSVNs with two optimization objectives(EDR minimization and entropy generation rate(EGR) minimization) is conducted. It is found that when the dimensionless mass flow rate(DMFR) is small, the optimal diameter ratio of the elemental XSVN derived by EDR minimization is different from that derived by EGR minimization. For the multilevel XSVN, when the DMFR is 100, compared the XSVN with the corresponding H-shaped vascular network(HSVN), the dimensionless EDRs of the elemental, second and fourth order XSVNs are reduced by 26.39%, 15.34% and 9.81%, respectively. Compared with the entransy dissipation number(EDN) of the second order XSVN before angle optimization, the EDN after optimization is reduced by 26.15%, which illustrates that it is significant to conduct angle optimization of the XSVN. Entransy theory is applied into the constructal design of the vasculature with heat transfer and fluid flow in this paper, which provides new directions for the vasculature designs.展开更多
The energy dissipation of X-shaped flaring gate piers ahead of a stepped spillway was adopted in the Suofengying Hydroplant. Under the circumstance that the first step is higher than others, at the step surface an aer...The energy dissipation of X-shaped flaring gate piers ahead of a stepped spillway was adopted in the Suofengying Hydroplant. Under the circumstance that the first step is higher than others, at the step surface an aerated cavity occured behind piers. The interaction of the weir head, the elevation difference between crest and chamber outlet, the first step height, the slopes of weir end and step, and the size of cavity, was investigated, the expression was derived to characterize their relationship, and the corresponding curves were plotted. The comparison of the calculated and simulated results with the measured data was performed. When the slopes of step and weir end are equivalent, the relative height difference between the first and second steps becomes the main factor influencing the aerated cavity. These findings may be useful in practical applications.展开更多
基金Project supported by the National Natural Science Foundation of China(No.U23A2066)the Liaoning Revitalization Talents Program of China(No.XLYC2202032)。
文摘Bionic X-shaped vibration isolators have been widely employed in aerospace and other industrial fields,but the stiffness properties of classic X-shaped structures limit the vibration isolation ability for low frequencies.An innovative bionic quasi-zero stiffness(QZS)vibration isolator(BQZSVI),which can broaden the QZS range of a classic X-shaped isolator and can bring it closer to the equilibrium position,is proposed.The BQZSVI consists of an X-shaped structure as the bone fabric of lower limbs and a nonlinear magnetic loop device simulating the leg muscle.Based on static calculation,the stiffness characteristic of the structure is confirmed.The governing equations of motion of the BQZSVI structure are established in the framework of the Lagrange equation,and the harmonic balance method(HBM)is adopted to obtain the transmissibility responses.The results show that the BQZSVI can provide a more accessible and broader range of QZS.In the dynamic manifestation,the introduction of the BQZSVI can reduce the amplitude of a classic X-shaped vibration isolator by 65.7%,and bring down the initial vibration isolation frequency from 7.43 Hz to 2.39 Hz.In addition,a BQZSVI prototype is designed and fabricated,and the exactitude of the theoretical analysis method is proven by means of experiments.
基金Project supported by the National Natural Science Foundation of China(Nos.12022213,12002329,U23A2066,12272240,and 12002217)。
文摘A novel X-shaped variable stiffness vibration isolator(X-VSVI)is proposed.The Runge-Kutta method,harmonic balance method,and wavelet transform spectra are introduced to evaluate the performance of the X-VSVI under various excitations.The layer number,the installation angle of the X-shaped structure,the stiffness,and the active control parameters are systematically analyzed.In addition,a prototype of the X-VSVI is manufactured,and vibration tests are carried out.The results show that the proposed X-VSVI has a superior adaptability to that of a traditional X-shaped mechanism,and shows excellent vibration isolation performance in response to different amplitudes and forms of excitations.Moreover,the vibration isolation efficiency of the device can be improved by appropriate adjustment of parameters.
基金the National Natural Science Foundation of China(No.12002195)the National Science Fund for Distinguished Young Scholars of China(No.12025204)+1 种基金the Program of Shanghai Municipal Education Commission of China(No.2019-01-07-00-09-E00018)the Pujiang Project of Shanghai Science and Technology Commission of China(No.20PJ1404000)。
文摘Existing quasi-zero stiffness(QZS)isolators are reviewed.In terms of their advantages,a novel X-shape QZS isolator combined with the cam-roller-spring mechanism(CRSM)is proposed.Different from the existing X-shape isolators,oblique springs are used to enhance the negative stiffness of the system.Meanwhile,the CRSM is used to eliminate the gravity of the loading mass,while the X-shape structure leaves its static position.The existing QZS isolators are demonstrated and classified according to their nonlinearity mechanisms and classical shapes.It is shown that the oblique spring can realize negative stiffness based on the simplest mechanism.The X-shape has a strong capacity of loading mass,while the CRSM can achieve a designed restoring force at any position.The proposed isolator combines all these advantages together.Based on the harmonic balance method(HBM)and the simulation,the displacement transmissibilities of the proposed isolator,the X-shape isolators just with oblique springs,and the X-shape isolators in the traditional form are studied.The results show that the proposed isolator has the lowest beginning isolation frequency and the smallest maximum displacement transmissibility.However,it still has some disadvantages similar to the existing QZS isolators.This means that its parameters should be designed carefully so as to avoid becoming a bistable system,in which there are two potential wells in the potential energy curve and thus the isolation performance will be worsened.
基金Supported by National Natural Science Foundation of China (No. 50878141)Hebei Natural Science Foundation,China (No. E2011202013)High School of Hebei Science and Technology Research Youth Foundation,China(No. Q2012083)
文摘To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement,two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial compression load and low reversed cyclic loading,which imitated low to moderate earthquake force.The seismic behavior of specially shaped column joints with X-shaped reinforcement in terms of bearing capacity,displacement,ductility,hysteretic curve,stiffness degradation and energy dissipation was studied and compared to that without Xshaped reinforcement in joint core region.With the damage estimation model,the accumulated damage was analyzed.The shearing capacity formula of specially shaped column joints reinforced by X-shaped reinforcement was proposed with a simple form.The test results show that X-shaped reinforcement is an effective measure for improving the seismic behavior of specially shaped column joints including deformation behavior,ductility and hysteretic characteristic.All specimens were damaged with gradual stiffness degeneration.In addition,X-shaped reinforcement in the joint core region is an effective way to lighten the degree of cumulated damage.The good seismic performance obtained from the specially shaped column joint with X-shaped reinforcement can be used in engineering applications.The test value is higher than the calculated value,which indicates that the formula is safe for the design of specially shaped column joints.
基金This work was supported by the National Natural Science Foundation of China(Grant No.29,070,196)and the Science Foundation of Polymer Physics Laboratory,Academia Sinica.
文摘The transitions and morphology of a series of main-chain liquid crystalline polymer with X-shaped mesogens were studied by means of DSC,SALS and polarizing microscopy techniques. Aneven-odd effect was observed for samples with different size of the substituents on the mesogenends. The isotropization process was similar to that of main-chain polymers with rod-likemesogens. No crystallization was detected for specimens cooling down from their isotropic meltstate. However two of the samples may crystallize in cooling process directly from the liquidcrystalline state.
基金This work was supported by the National Natural Science Foundation of China(No.29974026)the Natural Science Foundation of Henan Province.
文摘A novel series of main chain liquid crystalline copolyesters with X-shaped two-dimensional mesogenic unit and crown ether cycle of cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 was prepared via solution condensation polymerization from 4,4＇-（a;arhexanedioyloxy） dibenzoyl dichloride （MI）, 2,5-bis（p-octyloxybenzoyloxy） hydro-quinone （M2） and cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 （M3）. Monomer MI was synthesized by esterification and substitution of adipoyl chloride with p-hydroxybenzoic acid, monomer M2 was synthesized by esterfication and reduction reaction of 2,5-dihydroxybenzoquinone and p-octanoxybenzoyl chloride and monomer M3 was synthesized by diazotization and coupling reaction of cis-diaminodibenzo-18-crown-6 with phenol. The molecular weights of copolyesters are not high, and the intrinsic viscosity [η] of copolyesters ranges from 0.25-0.35. The monomers＇ structures were identified by using elemental analysis, IR, UV, ^1H-NMR, MS, etc. All the copolyesters are yellowish powders and insoluble in THF and CHC13 at room temperature except cPg. The properties of copolyesters were investigated by using GPC, [η] , DSC, TG, WAXD and POM. It was found that all the copolyesters entered into liquid crystal phase when they were heated to above their melting temperature （Tin）. The typical smectic and nematic phase texture can be observed on POM. Their mesophase transition temperature and thermal stability change regularly with varying the content of cis-4,4＇-bis（4-hydroxyphenylazo） dibenzo-18-crown-6 unit in the copolyesters.
基金The work was supported by the National Natural Science Foundation of China.
文摘A series of main chain liquid crystal aromatic copolyesters with X-shaped and rod-shaped mesogenic units were synthesized via solution condensation polymerizations of 4,4'-(alpha,omega-octanedioyloxy)-dibenzoyl dichlorides with 2,5-bis(p-octanoxy benzoyloxy)-hydroquinone and diphenol. All of the copolyesters showed thermotropic liquid crystalline behaviors through observations using DSC, polarized microscopy and X-ray diffraction. The melting point (T-m) and the isotropization temperature (T-i) change regularly with varying the content of diphenol unit in the copolymers.
文摘Musculoskeletal diseases such as neck, shoulder, back and leg pain are ext remely common in clinic. Diseases of the joints of the ext remi ti es, especially sputum, wr ist spr ains, and periarthritis of the shoulders, and even lumbar disc herniation, use X-shaped balance acupuncture therapy to relieve pain and improve motor function. The method of obtaining acupoints is simple and easy to operate. Many of clinical comparison shows that this therapy is simple to conventional acupuncture and moxibustion in the treatment of local pain and joint diseases. This review concluded the advantaged about the X-shaped balance acupuncture therapy and it worth to clinical promotion.
基金supported by the National Key Research and Development Program of China(No.2022YFC3004304)the National Natural Science Foundation of China(Grant No.52378209)+1 种基金the Hunan Province Science and Technology Project Huxiang Young Talents Program(No.2023RC3057)the Xiaohe SciTech Talents Special Funding under Hunan Provincial Sci-Tech Talents Sponsorship Program(No.2023TJ-X66).
文摘The high-speed railway track-bridge system(HSRTBS)is susceptible to damage under the effects of earthquakes,thus threatening the safety of running trains.To improve the seismic performance of HSRTBS and reduce damage to the system,a replaceable X-shaped Energy Dissipating Steel Damper(X-EDSD)is proposed,which contains the energy-dissipating component(EDC)to dissipate the earthquake energy.Cyclic tests were performed to obtain the hysteretic performance of the EDC and X-EDSD,and a test-validated numerical model was developed to conduct parametric analyses.The X-EDSD was simplified as a nonlinear spring element with hysteretic parameters and modeled into the numerical model of the HSRTBS for seismic dynamic analyses.The peak displacements of girder and rail decreased by approximately 48.1%and 47.7%,respectively.The peak deflections of the fasteners,cement asphalt mortar layer and sliding layer were reduced by 70.4%,70.8%,and 86.1%,respectively.A comprehensive consideration of the system response control-economic cost ratio coefficient R_(pe)is proposed,and the optimal thickness of 14.94 mm is obtained by applying cubic term coefficient fitting according to 5 groups of steel plate thickness data for the specific case study in this paper.The method can be used for cost-informed X-EDSD-selection for seismic mitigation of HSRTBS.
基金supported by the National Natural Science Foundation of China(Grant Nos.51506220,51579244)the Natural Science Foundation of Hubei Province(Grant No.2016CFB504)the Independent Project of Naval University of Engineering(Grant No.425317Q017)
文摘Combining with entransy theory, constructal designs of the X-shaped vascular networks(XSVNs) are implemented with fixed total tube volumes of the XSVNs. The entransy dissipation rates(EDRs) of the XSVNs are minimized, and the optimal constructs of the XSVNs are derived. Comparison of the optimal constructs of the XSVNs with two optimization objectives(EDR minimization and entropy generation rate(EGR) minimization) is conducted. It is found that when the dimensionless mass flow rate(DMFR) is small, the optimal diameter ratio of the elemental XSVN derived by EDR minimization is different from that derived by EGR minimization. For the multilevel XSVN, when the DMFR is 100, compared the XSVN with the corresponding H-shaped vascular network(HSVN), the dimensionless EDRs of the elemental, second and fourth order XSVNs are reduced by 26.39%, 15.34% and 9.81%, respectively. Compared with the entransy dissipation number(EDN) of the second order XSVN before angle optimization, the EDN after optimization is reduced by 26.15%, which illustrates that it is significant to conduct angle optimization of the XSVN. Entransy theory is applied into the constructal design of the vasculature with heat transfer and fluid flow in this paper, which provides new directions for the vasculature designs.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50479061).
文摘The energy dissipation of X-shaped flaring gate piers ahead of a stepped spillway was adopted in the Suofengying Hydroplant. Under the circumstance that the first step is higher than others, at the step surface an aerated cavity occured behind piers. The interaction of the weir head, the elevation difference between crest and chamber outlet, the first step height, the slopes of weir end and step, and the size of cavity, was investigated, the expression was derived to characterize their relationship, and the corresponding curves were plotted. The comparison of the calculated and simulated results with the measured data was performed. When the slopes of step and weir end are equivalent, the relative height difference between the first and second steps becomes the main factor influencing the aerated cavity. These findings may be useful in practical applications.
