This paper presents a fringe-carrier method that eliminates sign ambiguity of transient moire fringes which can be used to automatically determine the relative orders. A fringe carrier is preset in the static state of...This paper presents a fringe-carrier method that eliminates sign ambiguity of transient moire fringes which can be used to automatically determine the relative orders. A fringe carrier is preset in the static state of the specimen and the dynamic in-plane displacements are recorded as the modulation to the frequency of the carrier fringes when the specimen is loaded by impact. According to a modulating criterion developed from the modulation degree, the fringes of the transient moire patterns keep monotonical in orders so that they can be automatically encoded in grey levels by a digital image system. The moire orders purely caused by dynamic loadings are evaluated by subtracting the grey-value of the unmodulated carrier image from that of the modulated carrier images encoded by their orders. With the subtracted moire orders the strain components can be obtained, and, correspondingly, the histograms of dynamic displacement moire images are shown with order variation by image-difference.展开更多
Most soft materials behave as if they were hardened when subjected to an impact force. The strain rate dependence of viscosity resistance is the reason for this behavior. The authors carried out drop impact tests on s...Most soft materials behave as if they were hardened when subjected to an impact force. The strain rate dependence of viscosity resistance is the reason for this behavior. The authors carried out drop impact tests on several types of soft materials under the condition of a flat frontal impact. The impact force waveform of soft materials was found to consist of a thorn-shaped waveform and a succeeding mountain-shaped waveform. Based on our experimental observations, we believe that a large viscosity resistance is rapidly changed to a small resistance in the course of the impact. In the present study, the cause of this distinct waveform is discussed based on a dynamics model. The study applies a standard linear solid (SLS) model in which the viscosity transient phenomenon is considered is applied. Three types of impact force waveforms of actual soft materials are simulated using the SLS model. Some features of the impact force waveform of soft materials can be explained using the SLS model.展开更多
The exciton dynamics in a WS2 monolayer with strain are studied by transient absorption measurements.We measure the differential transmission signal from monolayer WS2 as a function of the probe wavelength at differen...The exciton dynamics in a WS2 monolayer with strain are studied by transient absorption measurements.We measure the differential transmission signal from monolayer WS2 as a function of the probe wavelength at different levels of strain applied to the sample.The differential transmission spectrum has a positive maximum value at about 614 nm and shows no significant strain dependence.By time-resolving the differential transmission signal,we find that the strain has a minimal effect on the exciton formation process.However,the exciton lifetime is significantly reduced by strain.These results provide useful information for applications of WS2 in flexible electronic and optoelectronic devices where strain is inevitable.展开更多
基金The project supported by Alexander von Humboldt Foundation or Germany and the National Natural Science Foundation of China
文摘This paper presents a fringe-carrier method that eliminates sign ambiguity of transient moire fringes which can be used to automatically determine the relative orders. A fringe carrier is preset in the static state of the specimen and the dynamic in-plane displacements are recorded as the modulation to the frequency of the carrier fringes when the specimen is loaded by impact. According to a modulating criterion developed from the modulation degree, the fringes of the transient moire patterns keep monotonical in orders so that they can be automatically encoded in grey levels by a digital image system. The moire orders purely caused by dynamic loadings are evaluated by subtracting the grey-value of the unmodulated carrier image from that of the modulated carrier images encoded by their orders. With the subtracted moire orders the strain components can be obtained, and, correspondingly, the histograms of dynamic displacement moire images are shown with order variation by image-difference.
文摘Most soft materials behave as if they were hardened when subjected to an impact force. The strain rate dependence of viscosity resistance is the reason for this behavior. The authors carried out drop impact tests on several types of soft materials under the condition of a flat frontal impact. The impact force waveform of soft materials was found to consist of a thorn-shaped waveform and a succeeding mountain-shaped waveform. Based on our experimental observations, we believe that a large viscosity resistance is rapidly changed to a small resistance in the course of the impact. In the present study, the cause of this distinct waveform is discussed based on a dynamics model. The study applies a standard linear solid (SLS) model in which the viscosity transient phenomenon is considered is applied. Three types of impact force waveforms of actual soft materials are simulated using the SLS model. Some features of the impact force waveform of soft materials can be explained using the SLS model.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFA0202302)the National Natural Science Foundation of China(Grant Nos.61527817 and 61875236)+3 种基金the Initiative Postdocs Supporting Program of China(Grant No.BX201600013)the General Financial Grant from the China Postdoctoral Science Foundation(Grant No.2017M610756)the Overseas Expertise Introduction Center for Discipline Innovation,Chinathe 111 Center of China
文摘The exciton dynamics in a WS2 monolayer with strain are studied by transient absorption measurements.We measure the differential transmission signal from monolayer WS2 as a function of the probe wavelength at different levels of strain applied to the sample.The differential transmission spectrum has a positive maximum value at about 614 nm and shows no significant strain dependence.By time-resolving the differential transmission signal,we find that the strain has a minimal effect on the exciton formation process.However,the exciton lifetime is significantly reduced by strain.These results provide useful information for applications of WS2 in flexible electronic and optoelectronic devices where strain is inevitable.
