A lumped mass gear-rattling model with backlash is established by considering the time varying mesh stiffness,composite transmission error and the torque fluctuation.Based on the principle that no separation will occu...A lumped mass gear-rattling model with backlash is established by considering the time varying mesh stiffness,composite transmission error and the torque fluctuation.Based on the principle that no separation will occur if the response amplitude is not larger than the static response,the threshold is obtained by theoretical derivation.The validity of the theoretical derivation is verified by the numerical method.The results show that the time-varying mesh stiffness has little effect on the threshold.When the exciting frequency is less than the system natural frequency,the theoretical agrees well with the numerical one.The higher the exciting frequency or the smaller the average input torque is,the easier the separation will occur.When the exciting frequency is larger than the natural frequency by a certain value,the theoretical threshold does not agree with the numerical results.The numerical results show that the motion state will change from the meshing state to the separating state directly.The phenomenon that the gear pair sometimes separates and sometimes meshes occurs only when the exciting frequency is smaller.展开更多
Rattling vibration is an important noise source of gear-box. To controlthat noise, it is necessary to elaborate a mathematics-mechanical model on rattlinggears. In this paper, a rattling system modulated by noise was ...Rattling vibration is an important noise source of gear-box. To controlthat noise, it is necessary to elaborate a mathematics-mechanical model on rattlinggears. In this paper, a rattling system modulated by noise was investigated. Insteadof performing the very tedious numerical calculation, a discrete stochastic modeldescribed by three dimensional mean mapping was established by means of the NonGaussian closure technique. Through the example, the chaotic stochastic behaviormay be revealed. In comparison with deterministic model, the model developed inthis paper is more approximate to practice adn more available for acousticinvestigation, so that it is suggested to be applied to modeling on rattling vibration.展开更多
Inspired by the excellent stability exhibited by experimentally synthesized two-dimensional(2D)MoSi_(2)N_(4) layered material,the thermal and electronic transport,and thermoelectric(TE)properties of MgAl2Te4 monolayer...Inspired by the excellent stability exhibited by experimentally synthesized two-dimensional(2D)MoSi_(2)N_(4) layered material,the thermal and electronic transport,and thermoelectric(TE)properties of MgAl2Te4 monolayer are systematically investigated using the First-principles calculations and Boltzmann transport theory.The mechanical stability,dynamic stability,and thermal stability(900 K)of the MgAl_(2)Te_(4) monolayer are demonstrated,respectively.The MgAl_(2)Te_(4) monolayer exhibits a bandgap of 1.35 eV using the HSE06 functional in combination with spin-orbit coupling(SOC)effect.Band convergence in the valence band is favorable to improve the thermoelectric properties.The rattling thermal damping effect caused by the weak bonding of Mgsingle bondTe bonds in MgAl2Te4 monolayer leads to ultra-low lattice thermal conductivity(0.95/0.38 W/(m·K)@300 K along the x-/y-direction),which is further demonstrated by the phonon group velocities,phonon relaxation time,Grüneisen parameters,and scattering mechanisms.The optimal zT of 3.28 at 900 K is achieved for the p-type MgAl_(2)Te_(4) monolayer,showing the great promising prospect for the excellent p-type thermoelectric material.Our current work not only reveals the underlying mechanisms responsible for the excellent TE properties,but also elaborates on the promising thermoelectric application of MgAl_(2)Te_(4) monolayer material at high temperature.展开更多
Bi_(1-x)Ho_(x)VO_(4)(0.1≤x≤0.9)ceramics were prepared via a solid-state reaction method,and all the ceram-ics could be well densified in the 920–980℃range.The ceramics with 0.1≤x<0.4 were composed of both mono...Bi_(1-x)Ho_(x)VO_(4)(0.1≤x≤0.9)ceramics were prepared via a solid-state reaction method,and all the ceram-ics could be well densified in the 920–980℃range.The ceramics with 0.1≤x<0.4 were composed of both monoclinic scheelite(M)and tetragonal zircon(T)phases,and a single M phase could be obtained in the range of x≥0.4.The measuredε_(r) decreased from 58.9(x=0.1)to 14.7(x=0.9),so do the calcu-lated values(ε_(r)(C−M)=34.3–12.1),and the main reason forε_(r)>ε_(r)(C−M)was the rattling of Ho^(3+)in the dodecahedron.Two points with zeroτf appeared in Bi1–x Hox VO4(0≤x≤1)ceramics,and the best mi-crowave dielectric properties withε_(r)=16.6,Q×f=18,400 GHz(f=10.69 GHz),andτf=+3.29 ppm/℃were obtained in the Bi_(0.2)Ho_(0.8)VO_(4)ceramic.The change in temperature coefficient of ionic polarizability(τ_(αm))caused by the rattling effect of cations is the physical essence that affectsτf.Therefore,the rattling effect can be used as an effective mechanism to regulateτf in low-ε_(r) materials.Furthermore,there was no chemical reaction between Bi_(1-x)Ho_(x)VO_(4) and Ag electrode,which indicates potential applications in low-temperature co-fired ceramic(LTCC)technology.展开更多
Virus-induced gene silencing(VIGS)is a natural defense mechanism of plants,which can cause sequence-specific degradation of viral RNA and is often used for studying the functional genome.At present,the VIGS system med...Virus-induced gene silencing(VIGS)is a natural defense mechanism of plants,which can cause sequence-specific degradation of viral RNA and is often used for studying the functional genome.At present,the VIGS system mediated by Tobacco rattle virus(TRV)has been successfully established in many plant species.However,the VIGS system in Chinese narcissus had not been reported yet.In this paper,the first use of the TRV-VIGS system in Chinese narcissus is described in detail.By injecting pTRV2-GFP into narcissus leaves,we confirmed that TRV could infect narcissus and move in narcissus plants.After the inoculation of pTRV2-Nt PDS by two methods,phenomena such as photo-bleaching appeared in narcissus leaves and qRT-PCR results proved that PDS gene of narcissus was successfully silenced.Besides,pTRV2-NtMYB3 was inoculated into basal plates of narcissus to study the function of NtMYB3;the results showed that NtMYB3 is an inhibitor of flavonoids biosynthesis,which can increase the content of proanthocyanidins in basal plates of narcissus by repressing the expression level of NtFLS.These results indicate that the TRV-VIGS system has been successfully established in Chinese narcissus and successfully applied to the functional study of NtMYB3.展开更多
基金This project is supported by National Natural Science Foundation of China(No.50075070).
文摘A lumped mass gear-rattling model with backlash is established by considering the time varying mesh stiffness,composite transmission error and the torque fluctuation.Based on the principle that no separation will occur if the response amplitude is not larger than the static response,the threshold is obtained by theoretical derivation.The validity of the theoretical derivation is verified by the numerical method.The results show that the time-varying mesh stiffness has little effect on the threshold.When the exciting frequency is less than the system natural frequency,the theoretical agrees well with the numerical one.The higher the exciting frequency or the smaller the average input torque is,the easier the separation will occur.When the exciting frequency is larger than the natural frequency by a certain value,the theoretical threshold does not agree with the numerical results.The numerical results show that the motion state will change from the meshing state to the separating state directly.The phenomenon that the gear pair sometimes separates and sometimes meshes occurs only when the exciting frequency is smaller.
文摘Rattling vibration is an important noise source of gear-box. To controlthat noise, it is necessary to elaborate a mathematics-mechanical model on rattlinggears. In this paper, a rattling system modulated by noise was investigated. Insteadof performing the very tedious numerical calculation, a discrete stochastic modeldescribed by three dimensional mean mapping was established by means of the NonGaussian closure technique. Through the example, the chaotic stochastic behaviormay be revealed. In comparison with deterministic model, the model developed inthis paper is more approximate to practice adn more available for acousticinvestigation, so that it is suggested to be applied to modeling on rattling vibration.
基金Financial supports from the National Natural Science Foundation of China(21503039)Department of Science and Technology of Liaoning Province(2019MS164)+1 种基金Department of Education of Liaoning Province(LJ2020JCL034)Discipline Innovation Team of Liaoning Technical University(LNTU20TD-16)are greatly acknowledged.
文摘Inspired by the excellent stability exhibited by experimentally synthesized two-dimensional(2D)MoSi_(2)N_(4) layered material,the thermal and electronic transport,and thermoelectric(TE)properties of MgAl2Te4 monolayer are systematically investigated using the First-principles calculations and Boltzmann transport theory.The mechanical stability,dynamic stability,and thermal stability(900 K)of the MgAl_(2)Te_(4) monolayer are demonstrated,respectively.The MgAl_(2)Te_(4) monolayer exhibits a bandgap of 1.35 eV using the HSE06 functional in combination with spin-orbit coupling(SOC)effect.Band convergence in the valence band is favorable to improve the thermoelectric properties.The rattling thermal damping effect caused by the weak bonding of Mgsingle bondTe bonds in MgAl2Te4 monolayer leads to ultra-low lattice thermal conductivity(0.95/0.38 W/(m·K)@300 K along the x-/y-direction),which is further demonstrated by the phonon group velocities,phonon relaxation time,Grüneisen parameters,and scattering mechanisms.The optimal zT of 3.28 at 900 K is achieved for the p-type MgAl_(2)Te_(4) monolayer,showing the great promising prospect for the excellent p-type thermoelectric material.Our current work not only reveals the underlying mechanisms responsible for the excellent TE properties,but also elaborates on the promising thermoelectric application of MgAl_(2)Te_(4) monolayer material at high temperature.
基金supported by the Natural Science Foundation of Guangxi Zhuang Autonomous Region(No.2023GXNSFBA026076)the Guangxi Key Laboratory of Optical and Electronic Materials and Devices(No.22KF-10)+1 种基金the Natural Science Foundation of China(Nos.21965009 and 22105048)the Guilin University of Technology Research Startup Project(No.GUTQDJJ2021073),and the Guangxi BaGui Scholars Special Funding.
文摘Bi_(1-x)Ho_(x)VO_(4)(0.1≤x≤0.9)ceramics were prepared via a solid-state reaction method,and all the ceram-ics could be well densified in the 920–980℃range.The ceramics with 0.1≤x<0.4 were composed of both monoclinic scheelite(M)and tetragonal zircon(T)phases,and a single M phase could be obtained in the range of x≥0.4.The measuredε_(r) decreased from 58.9(x=0.1)to 14.7(x=0.9),so do the calcu-lated values(ε_(r)(C−M)=34.3–12.1),and the main reason forε_(r)>ε_(r)(C−M)was the rattling of Ho^(3+)in the dodecahedron.Two points with zeroτf appeared in Bi1–x Hox VO4(0≤x≤1)ceramics,and the best mi-crowave dielectric properties withε_(r)=16.6,Q×f=18,400 GHz(f=10.69 GHz),andτf=+3.29 ppm/℃were obtained in the Bi_(0.2)Ho_(0.8)VO_(4)ceramic.The change in temperature coefficient of ionic polarizability(τ_(αm))caused by the rattling effect of cations is the physical essence that affectsτf.Therefore,the rattling effect can be used as an effective mechanism to regulateτf in low-ε_(r) materials.Furthermore,there was no chemical reaction between Bi_(1-x)Ho_(x)VO_(4) and Ag electrode,which indicates potential applications in low-temperature co-fired ceramic(LTCC)technology.
基金the Science and technology innovation fund of Fujian Agriculture and Forestry University(Grant Nos.KFA17352A,KFA17602A)。
文摘Virus-induced gene silencing(VIGS)is a natural defense mechanism of plants,which can cause sequence-specific degradation of viral RNA and is often used for studying the functional genome.At present,the VIGS system mediated by Tobacco rattle virus(TRV)has been successfully established in many plant species.However,the VIGS system in Chinese narcissus had not been reported yet.In this paper,the first use of the TRV-VIGS system in Chinese narcissus is described in detail.By injecting pTRV2-GFP into narcissus leaves,we confirmed that TRV could infect narcissus and move in narcissus plants.After the inoculation of pTRV2-Nt PDS by two methods,phenomena such as photo-bleaching appeared in narcissus leaves and qRT-PCR results proved that PDS gene of narcissus was successfully silenced.Besides,pTRV2-NtMYB3 was inoculated into basal plates of narcissus to study the function of NtMYB3;the results showed that NtMYB3 is an inhibitor of flavonoids biosynthesis,which can increase the content of proanthocyanidins in basal plates of narcissus by repressing the expression level of NtFLS.These results indicate that the TRV-VIGS system has been successfully established in Chinese narcissus and successfully applied to the functional study of NtMYB3.
