Decoupling the complicated vibrational-vibrational （V-V） coupling of a multimode vibrational relaxation remains a challenge for analyzing the sound relaxational absorption in multi-component gas mixtures. In our pre...Decoupling the complicated vibrational-vibrational （V-V） coupling of a multimode vibrational relaxation remains a challenge for analyzing the sound relaxational absorption in multi-component gas mixtures. In our previous work [Acta Phys. Sin. 61 174301 （2012）], an analytical model to predict the sound absorption from vibrational relaxation in a gas medium is proposed. In this paper, we develop the model to decouple the V-V coupled energy to each vibrationaltranslational deexcitation path, and analyze how the multimode relaxations form the peaks of sound absorption spectra in gas mixtures. We prove that a multimode relaxation is the sum of its decoupled single-relaxation processes, and only the decoupled process with a significant isochoric-molar-heat can be observed as an absorption peak. The decoupling model clarifies the essential processes behind the peaks in spectra arising from the multimode relaxations in multi-component gas mixtures. The simulation validates the proposed decoupling model.展开更多
Mooring system is the key equipment of FPSO safe operation. The soft yoke mooring system is regarded as one of the best shallow water mooring strategies and widely applied to the oil exploitation in the Bohai Bay in C...Mooring system is the key equipment of FPSO safe operation. The soft yoke mooring system is regarded as one of the best shallow water mooring strategies and widely applied to the oil exploitation in the Bohai Bay in China and the Gulf of Mexico. Based on the analysis of numerous monitoring data obtained by the prototype monitoring system of one FPSO in the Bohai Bay, the on-site lateral vibration behaviors found on the site of the soft yoke subject to wave load were analyzed. ADAMS simulation and model experiment were utilized to analyze the soft yoke lateral vibration and it was determined that lateral vibration was resonance behaviors caused by wave excitation. On the basis of the soft yoke longitudinal restoring force being guaranteed, a TLD-based vibration damper system was constructed and the vibration reduction experiments with multi-tank space and multi-load conditions were developed. The experimental results demonstrated that the proposed TLD vibration reduction system can effectively reduce lateral vibration of soft yoke structures.展开更多
Nonlinear energy sink(NES)can passively absorb broadband energy from primary oscillators.Proper multiple NESs connected in parallel exhibit superior performance to single-degree-of-freedom(SDOF)NESs.In this work,a lin...Nonlinear energy sink(NES)can passively absorb broadband energy from primary oscillators.Proper multiple NESs connected in parallel exhibit superior performance to single-degree-of-freedom(SDOF)NESs.In this work,a linear coupling spring is installed between two parallel NESs so as to expand the application scope of such vibration absorbers.The vibration absorption of the parallel and parallel-coupled NESs and the system response induced by the coupling spring are studied.The results show that the responses of the system exhibit a significant difference when the heavier cubic oscillators in the NESs have lower stiffness and the lighter cubic oscillators have higher stiffness.Moreover,the efficiency of the parallel-coupled NES is higher for medium shocks but lower for small and large shocks than that of the parallel NESs.The parallel-coupled NES also shows superior performance for medium harmonic excitations until higher response branches are induced.The performance of the parallel-coupled NES and the SDOF NES is compared.It is found that,regardless of the chosen SDOF NES parameters,the performance of the parallel-coupled NES is similar or superior to that of the SDOF NES in the entire force range.展开更多
Squeeze oil film damper are widely used in small high-speed aeroengine.But they are all made of high-hardness alloy steel. In order to improve their vibration absorption performance a new style of soft metal plated da...Squeeze oil film damper are widely used in small high-speed aeroengine.But they are all made of high-hardness alloy steel. In order to improve their vibration absorption performance a new style of soft metal plated damper has been studied. A coat of soft metal is plated on inner surface of the oil film ring, the surface will be deformed to some extent under the effect of oil film pressure. The characteristics of such dampers are calculated and analysed. Result shows that, compared with common damper, the new style damper can change oil film pressure distribution, enhance oil film damping, decrease stiffness, and reduce the force transfered to casing.展开更多
Honeycomb seals and shunt injection have been proposed to weaken the blade vibration.Honeycombseals,as well as,smooth seals were tested with different seals' clearances and shrouded blades.Theshunt injection was s...Honeycomb seals and shunt injection have been proposed to weaken the blade vibration.Honeycombseals,as well as,smooth seals were tested with different seals' clearances and shrouded blades.Theshunt injection was sprayed to the blade tip clearance in the reverse direction of the main flow.Experi-mental results showed that both honeycomb seals and shunt injection had the damping effect for blade vi-bration,and the blade vibration magnitude could be reduced by more than 25 % and 17 %,respectively.When the two methods were adopted synchronously,more than 1/3 of the blade vibration could be re-duced.Consequently,adopting honeycomb seal and superinducing proper shunt injection are two usefulways to minimize vibration of the blade from the viewpoints of avoiding blade rupture and improving therotor stability.展开更多
As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness.To address thes...As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness.To address these challenges,we propose a novel tunable electromagnetic semi-active dynamic vibration absorber(ESADVA),which integrates with a magnetic suction follower to form a followed ESADVA(follow-ESADVA)for mirror milling.This system combines a tunable magnet oscillator with a follower,enabling real-time vibration absorption and condition feedback throughout the milling process.Additionally,the device supports self-sensing and frequency adjustment by providing feedback to a linear actuator,which alters the distance between magnets.This resolves the traditional issue of being unable to directly monitor vibration at the machining point due to space constraints and tool interference.The frequency shift characteristics and vibration absorption performance are comprehensively investigated.Theoretical and experimental results demonstrate that the prototyped follow-ESADVA achieves frequency synchronization with the milling tool,resulting in a vibration suppression rate of approximately 47.57%.Moreover,the roughness of the machined surface decreases by18.95%,significantly enhancing the surface quality.The results of this work pave the way for higher-quality machined surfaces and a more stable mirror milling process.展开更多
This paper presents the design of a novel honeycomb structure with a double curved beam.The purpose of this design is to achieve vibration isolation for the main engine of an offshore platform and reduce impact loads....This paper presents the design of a novel honeycomb structure with a double curved beam.The purpose of this design is to achieve vibration isolation for the main engine of an offshore platform and reduce impact loads.An analytical formula for the force-displacement relationship of the honeycomb single-cell structure is presented based on the modal superposition method.This formula provides a theoretical basis for predicting the compression performance of honeycomb structures.The effects of structural geometric parameters,series and parallel connection methods on the mechanical and energy absorption properties are investigated through mathematical modeling and experimental methods.Furthermore,the study focuses on the vibration isolation and impact resistance performance of honeycomb panels.The results show that the designed honeycomb structure has good mechanical and energy absorption performance,and its energy absorption effect is related to the geometric parameters and series and parallel connection methods of the structure.The isolation efficiency of the honeycomb with 4 rows and 3 columns reaches 38%.The initial isolation frequency of the isolator is 11.7 Hz.展开更多
Traditional passive vibration absorbers are effective only when their natural frequencies are close to those of the excitations. To solve this problem, a vibration absorber with time-delayed feedback control is propos...Traditional passive vibration absorbers are effective only when their natural frequencies are close to those of the excitations. To solve this problem, a vibration absorber with time-delayed feedback control is proposed to suppress vibration of the primary system under excitation with changing frequency. Firstly, the mechanical model of the delay coupled system is established. Then, the displacement transfer ratio of the system is obtained. The stability of the system is analyzed since delay may result in destabilization. Next, in order to design the control parameters, the vibration absorption performances of the proposed time-delayed vibration absorber are studied. The vibration absorption region is shown. The results show that time-delayed feedback control is able to change the response of the system. The effective vibration absorption frequency band is adjustable by tuning the control gain and time delay. The effective frequency band can be widened when choosing appropriate control parameters. The vibration absorption performances can be greatly improved by the time-delayed absorber. In addition, the optimum control parameters are obtained. Finally, the experimental prototype is constructed. Several tests with different control parameters are taken. The experimental and analytical results match quite well.展开更多
The absorption spectrum of the cyclotrime-thylenetrinitramine （RDX） with four different particle sizes are measured in the frequency range from 0.1THz to 2.5THz by using the terahertz time-domain spectroscopy （THz-...The absorption spectrum of the cyclotrime-thylenetrinitramine （RDX） with four different particle sizes are measured in the frequency range from 0.1THz to 2.5THz by using the terahertz time-domain spectroscopy （THz-TDS）, and the characteristic absorption peaks are acquired. All the samples are measured in a loose condition, which is very close to the real using environment of the RDX. The results show that the four kinds of samples have similar absorption peaks around the frequency of 0.82THz, 1.05 THz, 1.30THz, 1.46THz, 1.65THz, and 1.95THz. The sample with a large particle size obtains more peaks than the small one, while the peaks obtained from the sample with a small size are more protrudent. The reasons for these differences can be the refraction, scattering, and attenuation of the terahertz wave when it passes through the crystal samples. The theoretical terahertz spectrum of RDX was simulated by using density functional calculations, in which, the Becke ＆amp; Perdew-Wang＇s functional is used in a double numerical plus polarization method （BP/DNP）. Good agreements between the experimental and computed results show that the three peaks located in the frequency of 1.30THz, 1.48THz, and 1.96THz are caused respectively by the twisting of three-nitrogen heterocyclic, the symmetrical oscillations of the double nitro groups, and the oscillations of a single nitro group.展开更多
The infrared absorption spectrum of zinc oxide whiskers with tetrapod shape was recorded and compared with ZnO powder. The absorptions of microwave and sound were investigated with a result showing that the ZnO whisk...The infrared absorption spectrum of zinc oxide whiskers with tetrapod shape was recorded and compared with ZnO powder. The absorptions of microwave and sound were investigated with a result showing that the ZnO whiskers are of excellence as absorbents of microwave and soundproofing. The results of vibration damping tests of polyvinyl chloride indicate that the material containing the tetrapod shaped ZnO whiskers appears superior damping characteristics.展开更多
In this study,a coupling model of fluid-conveying pipes made of functionally graded materials(FGMs)with NiTiNOL-steel(NiTi-ST)for vibration absorption is investigated.The vibration responses of the FGM fluid-conveying...In this study,a coupling model of fluid-conveying pipes made of functionally graded materials(FGMs)with NiTiNOL-steel(NiTi-ST)for vibration absorption is investigated.The vibration responses of the FGM fluid-conveying pipe with NiTi-ST are studied by the Galerkin truncation method(GTM)and harmonic balance method(HBM).The harmonic balance solutions and the numerical results are consistent.Also,the linearized stability of the structure is determined.The effects of the structure parameters on the absorption performance are also studied.The results show that the NiTi-ST is an effective means of vibration absorption.Furthermore,in studying the effect of the NiTi-ST,a closed detached response(CDR)is first observed.It is noteworthy that the CDR may dramatically change the vibration amplitude and that the parameters of the NiTi-ST may determine the emergence or disappearance of the CDR.This vibration absorption device can be extended to offer more general vibration control in engineering applications.展开更多
The vibroacoustic response and sound absorption performance of a structure composed of multilayer plates and one rigid back wall are theoretically analyzed. In this structure, all plates are two-dimensional, microperf...The vibroacoustic response and sound absorption performance of a structure composed of multilayer plates and one rigid back wall are theoretically analyzed. In this structure, all plates are two-dimensional, microperforated, and periodically rib-stiffened. To investigate such a structural system, semianalytical models of one-layer and multilayer plate structures considering the vibration effects are first developed. Then approaches of the space harmonic method and Fourier transforms are applied to a one-layer plate, and finally the cascade connection method is utilized for a multilayer plate structure. Based on fundamental acoustic formulas, the vibroacoustic responses of microperforated stiffened plates are expressed as functions of a series of harmonic amplitudes of plate displacement, which are then solved by employing the numerical truncation method. Applying the inverse Fourier transform, wave propagation, and linear addition properties, the equations of the sound pressures and absorption coefficients for the one-layer and multilayer stiffened plates in physical space are finally derived. Using numerical examples, the effects of the most important physical parameters-for example, the perforation ratio of the plate, sound incident angles, and periodical rib spacing-on sound absorption performance are examined. Numerical results indicate that the sound absorption performance of the studied structure is effectively enhanced by the flexural vibration of the plate in water. Finally, the proposed approaches are validated by comparing the results of stiffened plates of the present work with solutions from previous studies.展开更多
The local vibration mode(LVM)of carbon acceptor in GaAs is studied by measuring directly the change in LVM absorption with a NIC-170 SX FT-IR spectrometer.The change in the charge state of carbon acceptor and the temp...The local vibration mode(LVM)of carbon acceptor in GaAs is studied by measuring directly the change in LVM absorption with a NIC-170 SX FT-IR spectrometer.The change in the charge state of carbon acceptor and the temperature dependence of the LVM absorption were investigated also.The contents of the impurities other than carbon were estimated by secondary ion mass spectrometry.It is observed that the frequency,the spectral form and the integrated absorption of the LVM are not affected by the change in charge state of car- bon acceptor.展开更多
N-doped FZ-Si crystals and N-doped NTD FZ-Si crystals and their annealing behavior have been studied by IR spectrum. Two models of nitrogen configuration, nearly substitutional nitrogen and interstitial nitrogen pair,...N-doped FZ-Si crystals and N-doped NTD FZ-Si crystals and their annealing behavior have been studied by IR spectrum. Two models of nitrogen configuration, nearly substitutional nitrogen and interstitial nitrogen pair, have been proposed and two nitrogen-related IR absorption peaks at 767cm-1 and 963cm-1 have been well explained.展开更多
Coherent vibrational dynamics can be observed in atomically precise gold nanoclusters using femtosecond time-resolved pump-probe spectroscopy.It can not only reveal the coupling between electrons and vibrations,but al...Coherent vibrational dynamics can be observed in atomically precise gold nanoclusters using femtosecond time-resolved pump-probe spectroscopy.It can not only reveal the coupling between electrons and vibrations,but also reflect the mechanical and electronic properties of metal nanoclusters,which holds potential applications in biological sensing and mass detection.Here,we investigated the coherent vibrational dynamics of[Au_(25)(SR)_(18)]^(-)nanoclusters by ultrafast spectroscopy and revealed the origins of thesecoherent vibrations by analyzing their frequency,phase and probe wavelength distributions.Strong coherent oscillations with frequency of 40 cm^(-1) and 80 cm^(-1) can be reproduced in the excited state dynamics of[Au_(25)(SR)_(18)]^(-),which should originate from acoustic vibrations of the Au13 metal core.Phase analysis on the oscillations indicates that the 80 cm^(-1) mode should arise from the frequency modulation of the electronic states while the 40 cm^(-1) mode should originate from the amplitude modulation of the dynamic spectrum.Moreover,it is found that the vibration frequencies of[Au_(25)(SR)_(18)]^(-)obtained in pump-probe measurements are independent of the surface ligands so that they are intrinsic properties of the metal core.These results are of great value to understand the electron-vibration coupling of metal nanoclusters.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 60971009 and 61001011)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20090142110019)+1 种基金the Natural Science Foundation of Hubei Province, China (Grant No. 2010CDB02701)the Fundamental Research Funds for the Central Universities, China (Grant No. 2012QN083)
文摘Decoupling the complicated vibrational-vibrational （V-V） coupling of a multimode vibrational relaxation remains a challenge for analyzing the sound relaxational absorption in multi-component gas mixtures. In our previous work [Acta Phys. Sin. 61 174301 （2012）], an analytical model to predict the sound absorption from vibrational relaxation in a gas medium is proposed. In this paper, we develop the model to decouple the V-V coupled energy to each vibrationaltranslational deexcitation path, and analyze how the multimode relaxations form the peaks of sound absorption spectra in gas mixtures. We prove that a multimode relaxation is the sum of its decoupled single-relaxation processes, and only the decoupled process with a significant isochoric-molar-heat can be observed as an absorption peak. The decoupling model clarifies the essential processes behind the peaks in spectra arising from the multimode relaxations in multi-component gas mixtures. The simulation validates the proposed decoupling model.
基金supported by the National Natural Science Foundation of China(Grant No.11572072)the National Key Basic Research and Development Program of China(Grant Nos.2014CB046803 and 2016ZX05028-002-005)
文摘Mooring system is the key equipment of FPSO safe operation. The soft yoke mooring system is regarded as one of the best shallow water mooring strategies and widely applied to the oil exploitation in the Bohai Bay in China and the Gulf of Mexico. Based on the analysis of numerous monitoring data obtained by the prototype monitoring system of one FPSO in the Bohai Bay, the on-site lateral vibration behaviors found on the site of the soft yoke subject to wave load were analyzed. ADAMS simulation and model experiment were utilized to analyze the soft yoke lateral vibration and it was determined that lateral vibration was resonance behaviors caused by wave excitation. On the basis of the soft yoke longitudinal restoring force being guaranteed, a TLD-based vibration damper system was constructed and the vibration reduction experiments with multi-tank space and multi-load conditions were developed. The experimental results demonstrated that the proposed TLD vibration reduction system can effectively reduce lateral vibration of soft yoke structures.
基金the National Natural Science Foundation of China(Nos.11872274 and11702188)the Tianjin Natural Science Foundation of China(No.18JCYBJC19900)。
文摘Nonlinear energy sink(NES)can passively absorb broadband energy from primary oscillators.Proper multiple NESs connected in parallel exhibit superior performance to single-degree-of-freedom(SDOF)NESs.In this work,a linear coupling spring is installed between two parallel NESs so as to expand the application scope of such vibration absorbers.The vibration absorption of the parallel and parallel-coupled NESs and the system response induced by the coupling spring are studied.The results show that the responses of the system exhibit a significant difference when the heavier cubic oscillators in the NESs have lower stiffness and the lighter cubic oscillators have higher stiffness.Moreover,the efficiency of the parallel-coupled NES is higher for medium shocks but lower for small and large shocks than that of the parallel NESs.The parallel-coupled NES also shows superior performance for medium harmonic excitations until higher response branches are induced.The performance of the parallel-coupled NES and the SDOF NES is compared.It is found that,regardless of the chosen SDOF NES parameters,the performance of the parallel-coupled NES is similar or superior to that of the SDOF NES in the entire force range.
文摘Squeeze oil film damper are widely used in small high-speed aeroengine.But they are all made of high-hardness alloy steel. In order to improve their vibration absorption performance a new style of soft metal plated damper has been studied. A coat of soft metal is plated on inner surface of the oil film ring, the surface will be deformed to some extent under the effect of oil film pressure. The characteristics of such dampers are calculated and analysed. Result shows that, compared with common damper, the new style damper can change oil film pressure distribution, enhance oil film damping, decrease stiffness, and reduce the force transfered to casing.
基金the National Natural Science Foundation of China(No.50375013,50675013)the National High Technology Research and Development Progamme of China(No.2007AA04Z422)
文摘Honeycomb seals and shunt injection have been proposed to weaken the blade vibration.Honeycombseals,as well as,smooth seals were tested with different seals' clearances and shrouded blades.Theshunt injection was sprayed to the blade tip clearance in the reverse direction of the main flow.Experi-mental results showed that both honeycomb seals and shunt injection had the damping effect for blade vi-bration,and the blade vibration magnitude could be reduced by more than 25 % and 17 %,respectively.When the two methods were adopted synchronously,more than 1/3 of the blade vibration could be re-duced.Consequently,adopting honeycomb seal and superinducing proper shunt injection are two usefulways to minimize vibration of the blade from the viewpoints of avoiding blade rupture and improving therotor stability.
基金Project supported by the National Natural Science Foundation of China(Nos.12172248,12021002,12302022,and 12132010)the Tianjin Research Program of Application Foundation and Advanced Technology of China(No.22JCQNJC00780)IoT Standards and Application Key Laboratory of the Ministry of Industry and Information Technology of China(No.202306)。
文摘As critical components of aircraft skins and rocket fuel storage tank shells,large thin-walled workpieces are susceptible to vibration and deformation during machining due to their weak local stiffness.To address these challenges,we propose a novel tunable electromagnetic semi-active dynamic vibration absorber(ESADVA),which integrates with a magnetic suction follower to form a followed ESADVA(follow-ESADVA)for mirror milling.This system combines a tunable magnet oscillator with a follower,enabling real-time vibration absorption and condition feedback throughout the milling process.Additionally,the device supports self-sensing and frequency adjustment by providing feedback to a linear actuator,which alters the distance between magnets.This resolves the traditional issue of being unable to directly monitor vibration at the machining point due to space constraints and tool interference.The frequency shift characteristics and vibration absorption performance are comprehensively investigated.Theoretical and experimental results demonstrate that the prototyped follow-ESADVA achieves frequency synchronization with the milling tool,resulting in a vibration suppression rate of approximately 47.57%.Moreover,the roughness of the machined surface decreases by18.95%,significantly enhancing the surface quality.The results of this work pave the way for higher-quality machined surfaces and a more stable mirror milling process.
基金supported by the National Natural Science Foundation of China(Grant No.52088102)the Major Scientific and Technological Innovation Project of Shandong Province(Grant No.2019JZZY010820).
文摘This paper presents the design of a novel honeycomb structure with a double curved beam.The purpose of this design is to achieve vibration isolation for the main engine of an offshore platform and reduce impact loads.An analytical formula for the force-displacement relationship of the honeycomb single-cell structure is presented based on the modal superposition method.This formula provides a theoretical basis for predicting the compression performance of honeycomb structures.The effects of structural geometric parameters,series and parallel connection methods on the mechanical and energy absorption properties are investigated through mathematical modeling and experimental methods.Furthermore,the study focuses on the vibration isolation and impact resistance performance of honeycomb panels.The results show that the designed honeycomb structure has good mechanical and energy absorption performance,and its energy absorption effect is related to the geometric parameters and series and parallel connection methods of the structure.The isolation efficiency of the honeycomb with 4 rows and 3 columns reaches 38%.The initial isolation frequency of the isolator is 11.7 Hz.
基金the National Natural Science Foundation of China (Grants 11572224 and 11772229).
文摘Traditional passive vibration absorbers are effective only when their natural frequencies are close to those of the excitations. To solve this problem, a vibration absorber with time-delayed feedback control is proposed to suppress vibration of the primary system under excitation with changing frequency. Firstly, the mechanical model of the delay coupled system is established. Then, the displacement transfer ratio of the system is obtained. The stability of the system is analyzed since delay may result in destabilization. Next, in order to design the control parameters, the vibration absorption performances of the proposed time-delayed vibration absorber are studied. The vibration absorption region is shown. The results show that time-delayed feedback control is able to change the response of the system. The effective vibration absorption frequency band is adjustable by tuning the control gain and time delay. The effective frequency band can be widened when choosing appropriate control parameters. The vibration absorption performances can be greatly improved by the time-delayed absorber. In addition, the optimum control parameters are obtained. Finally, the experimental prototype is constructed. Several tests with different control parameters are taken. The experimental and analytical results match quite well.
基金was supported by the National Natural Science Foundation of China under Grant No. U1330202 and 11204279the Foundation of Terahertz Research Center, CAEP under Grant No. T2014-005-0103
文摘The absorption spectrum of the cyclotrime-thylenetrinitramine （RDX） with four different particle sizes are measured in the frequency range from 0.1THz to 2.5THz by using the terahertz time-domain spectroscopy （THz-TDS）, and the characteristic absorption peaks are acquired. All the samples are measured in a loose condition, which is very close to the real using environment of the RDX. The results show that the four kinds of samples have similar absorption peaks around the frequency of 0.82THz, 1.05 THz, 1.30THz, 1.46THz, 1.65THz, and 1.95THz. The sample with a large particle size obtains more peaks than the small one, while the peaks obtained from the sample with a small size are more protrudent. The reasons for these differences can be the refraction, scattering, and attenuation of the terahertz wave when it passes through the crystal samples. The theoretical terahertz spectrum of RDX was simulated by using density functional calculations, in which, the Becke ＆amp; Perdew-Wang＇s functional is used in a double numerical plus polarization method （BP/DNP）. Good agreements between the experimental and computed results show that the three peaks located in the frequency of 1.30THz, 1.48THz, and 1.96THz are caused respectively by the twisting of three-nitrogen heterocyclic, the symmetrical oscillations of the double nitro groups, and the oscillations of a single nitro group.
文摘The infrared absorption spectrum of zinc oxide whiskers with tetrapod shape was recorded and compared with ZnO powder. The absorptions of microwave and sound were investigated with a result showing that the ZnO whiskers are of excellence as absorbents of microwave and soundproofing. The results of vibration damping tests of polyvinyl chloride indicate that the material containing the tetrapod shaped ZnO whiskers appears superior damping characteristics.
基金Project supported by the National Natural Science Foundation of China(Nos.12272240 and12022213)。
文摘In this study,a coupling model of fluid-conveying pipes made of functionally graded materials(FGMs)with NiTiNOL-steel(NiTi-ST)for vibration absorption is investigated.The vibration responses of the FGM fluid-conveying pipe with NiTi-ST are studied by the Galerkin truncation method(GTM)and harmonic balance method(HBM).The harmonic balance solutions and the numerical results are consistent.Also,the linearized stability of the structure is determined.The effects of the structure parameters on the absorption performance are also studied.The results show that the NiTi-ST is an effective means of vibration absorption.Furthermore,in studying the effect of the NiTi-ST,a closed detached response(CDR)is first observed.It is noteworthy that the CDR may dramatically change the vibration amplitude and that the parameters of the NiTi-ST may determine the emergence or disappearance of the CDR.This vibration absorption device can be extended to offer more general vibration control in engineering applications.
基金supported by the National Natural Science Foundation of China (Grants 51405276, 51505261, and 50875030)the Natural Science Foundation of Shandong Province, China (Grants ZR2014EEQ019 and ZR2014EEP025)the Foundation for Young Teacher Development of the Shandong University of Technology
文摘The vibroacoustic response and sound absorption performance of a structure composed of multilayer plates and one rigid back wall are theoretically analyzed. In this structure, all plates are two-dimensional, microperforated, and periodically rib-stiffened. To investigate such a structural system, semianalytical models of one-layer and multilayer plate structures considering the vibration effects are first developed. Then approaches of the space harmonic method and Fourier transforms are applied to a one-layer plate, and finally the cascade connection method is utilized for a multilayer plate structure. Based on fundamental acoustic formulas, the vibroacoustic responses of microperforated stiffened plates are expressed as functions of a series of harmonic amplitudes of plate displacement, which are then solved by employing the numerical truncation method. Applying the inverse Fourier transform, wave propagation, and linear addition properties, the equations of the sound pressures and absorption coefficients for the one-layer and multilayer stiffened plates in physical space are finally derived. Using numerical examples, the effects of the most important physical parameters-for example, the perforation ratio of the plate, sound incident angles, and periodical rib spacing-on sound absorption performance are examined. Numerical results indicate that the sound absorption performance of the studied structure is effectively enhanced by the flexural vibration of the plate in water. Finally, the proposed approaches are validated by comparing the results of stiffened plates of the present work with solutions from previous studies.
文摘The local vibration mode(LVM)of carbon acceptor in GaAs is studied by measuring directly the change in LVM absorption with a NIC-170 SX FT-IR spectrometer.The change in the charge state of carbon acceptor and the temperature dependence of the LVM absorption were investigated also.The contents of the impurities other than carbon were estimated by secondary ion mass spectrometry.It is observed that the frequency,the spectral form and the integrated absorption of the LVM are not affected by the change in charge state of car- bon acceptor.
文摘N-doped FZ-Si crystals and N-doped NTD FZ-Si crystals and their annealing behavior have been studied by IR spectrum. Two models of nitrogen configuration, nearly substitutional nitrogen and interstitial nitrogen pair, have been proposed and two nitrogen-related IR absorption peaks at 767cm-1 and 963cm-1 have been well explained.
基金supported by the startup funding from University of Science and Technology of China(KY2340000137)the startup funding from Chinese Academy of Sciences
文摘Coherent vibrational dynamics can be observed in atomically precise gold nanoclusters using femtosecond time-resolved pump-probe spectroscopy.It can not only reveal the coupling between electrons and vibrations,but also reflect the mechanical and electronic properties of metal nanoclusters,which holds potential applications in biological sensing and mass detection.Here,we investigated the coherent vibrational dynamics of[Au_(25)(SR)_(18)]^(-)nanoclusters by ultrafast spectroscopy and revealed the origins of thesecoherent vibrations by analyzing their frequency,phase and probe wavelength distributions.Strong coherent oscillations with frequency of 40 cm^(-1) and 80 cm^(-1) can be reproduced in the excited state dynamics of[Au_(25)(SR)_(18)]^(-),which should originate from acoustic vibrations of the Au13 metal core.Phase analysis on the oscillations indicates that the 80 cm^(-1) mode should arise from the frequency modulation of the electronic states while the 40 cm^(-1) mode should originate from the amplitude modulation of the dynamic spectrum.Moreover,it is found that the vibration frequencies of[Au_(25)(SR)_(18)]^(-)obtained in pump-probe measurements are independent of the surface ligands so that they are intrinsic properties of the metal core.These results are of great value to understand the electron-vibration coupling of metal nanoclusters.
