Phase change materials(PCMs)are important for sustaining energy development.For the thermal performance enhancement,the composite PCM with metal foam reconstructed by the Voronoi method is investigated in this work.Th...Phase change materials(PCMs)are important for sustaining energy development.For the thermal performance enhancement,the composite PCM with metal foam reconstructed by the Voronoi method is investigated in this work.The lattice Boltzmann method(LBM)is used to analyze the melting process on a pore scale.The melting interface evolution and temperature contour of the composite PCM are explored and compared with those of pure PCM.Moreover,structure parameters including the pore density,porosity and irregularity are investigated comprehensively,indicating that the additive of metal foam strengthens the melting performance of PCM obviously.Compared with pure PCM,the composite PCM has quick rates of the melting front evolution and heat transfer.The heat conduction plays a great role in the whole melting process since the convection is weakened for the composite PCM.To improve the melting efficiency,a larger pore density and smaller irregularity are recommended in general.More significantly,a suitable porosity is determined based on the requirement for the balance between the melting rate and heat storage capacity in practical engineering.展开更多
The stochastic response of a noisy system with non-negative restoring force is investigated. The generalized cell mapping （GCM） method compute the transient and stationary probability density functions （PDFs） real...The stochastic response of a noisy system with non-negative restoring force is investigated. The generalized cell mapping （GCM） method compute the transient and stationary probability density functions （PDFs） real-power is used to Combined with the global properties of the noise-free system, the evolutionary process of the tran- sient PDFs is revealed. The results show that stochastic P-bifurcation occurs when the system parameter varies in the response analysis and the stationary PDF evolves from bimodal to unimodal along the unstable manifold during the bifurcation.展开更多
A multi-channel synchronous demodulation system of a polarized low-coherence interferometer(PLCI)based on a matrix charge-coupled-device(CCD)is proposed and demonstrated.By using special designs,the system allows the ...A multi-channel synchronous demodulation system of a polarized low-coherence interferometer(PLCI)based on a matrix charge-coupled-device(CCD)is proposed and demonstrated.By using special designs,the system allows the signals from different channels to be received and demodulated synchronously.Multichannel air pressure experiments were implemented to verify the effectiveness of the proposed system.The experiment results showed that the Fabry–Perot(F–P)sensors could be demodulated synchronously with a high tolerance for light sources and sensors,which indicated that any sensor and light source that can be demodulated by PLCI were allowed to be employed,leading to a wide application in the field of multichannel synchronous measurement.展开更多
A novel magnetic field sensing system based on the fiber loop ring-down technique is proposed in this paper. In the fiber loop, a U-bent single-mode-fiber structure coated with magnetic fluid(MF) serves as the sensing...A novel magnetic field sensing system based on the fiber loop ring-down technique is proposed in this paper. In the fiber loop, a U-bent single-mode-fiber structure coated with magnetic fluid(MF) serves as the sensing head, and an erbium-doped fiber amplifier(EDFA) is introduced to compensate for the intrinsic loss of the cavity. The ring-down time of the system varies with the change of applied magnetic field due to the tunable absorption coefficient and refractive index of the MF. Therefore, measurement of the magnetic field can be realized by monitoring the ringdown time. The experimental results show that the performance of the system is extremely dependent on the interrogation wavelength, because both the gain of the EDFA and the loss of the sensing head are wavelength dependent.We found that at the optimal wavelength, the ratio of the gain to loss attained its maximum. The sensing system was experimentally demonstrated and a sensitivity of-0.5951 μs∕Oe was achieved.展开更多
Electromagnetically induced transparency(EIT)phenomenon is observed in simple metamaterial which consists of concentric double U-shaped resonators(USRs).The numerical and theoretical analysis reveals that EIT arises f...Electromagnetically induced transparency(EIT)phenomenon is observed in simple metamaterial which consists of concentric double U-shaped resonators(USRs).The numerical and theoretical analysis reveals that EIT arises from the bright-bright mode coupling.The transmission spectra at different polarization angle of incident light shows that EIT transparency window is polarization sensitive.More interestingly,Fano resonance appears in the transmission spectrum at certain polarization angles.The sharp and asymmetric Fano lineshape is high valuable for sensing.The performance of sensor is investigated and the sensitivity is high up to 327 GHz/RIU.Furthermore,active control of EIT window is realized by incorporating photosensitive silicon.The proposed USR structure is simple and compact,which may find significant applications in tunable integrated devices such as biosensor,filters,and THz modulators.展开更多
In this paper, Er/Yb co-doped fiber amplifiers(EYDFAs) with an Yb-band fiber Bragg grating(FBG) at the pump end to improve the performance of the amplifier is systematically studied. The influence of the reflectivity ...In this paper, Er/Yb co-doped fiber amplifiers(EYDFAs) with an Yb-band fiber Bragg grating(FBG) at the pump end to improve the performance of the amplifier is systematically studied. The influence of the reflectivity and center wavelength of the FBG along with the gain-fiber length on the performance of an EYDFA are numerically analyzed. The results show that the wavelength of the FBG has critical influence on the efficiency of the EYDFA,whereas the requirement to its reflectivity is relaxed. It is an effective and promising way to improve the efficiency of a high-power pumped EYDFA by introducing a suitable Yb-band FBG at the pump end. Based on the analysis of the underlying principles, suggestions for the practical design and possible further improvement strategies are also proposed.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.51876184,51725602,and 51806147)the Natural Science Foundation of Jiangsu Province,China(Grant No.BK20180102).
文摘Phase change materials(PCMs)are important for sustaining energy development.For the thermal performance enhancement,the composite PCM with metal foam reconstructed by the Voronoi method is investigated in this work.The lattice Boltzmann method(LBM)is used to analyze the melting process on a pore scale.The melting interface evolution and temperature contour of the composite PCM are explored and compared with those of pure PCM.Moreover,structure parameters including the pore density,porosity and irregularity are investigated comprehensively,indicating that the additive of metal foam strengthens the melting performance of PCM obviously.Compared with pure PCM,the composite PCM has quick rates of the melting front evolution and heat transfer.The heat conduction plays a great role in the whole melting process since the convection is weakened for the composite PCM.To improve the melting efficiency,a larger pore density and smaller irregularity are recommended in general.More significantly,a suitable porosity is determined based on the requirement for the balance between the melting rate and heat storage capacity in practical engineering.
基金Project supported by the National Natural Science Foundation of China(Nos.11172233,11302169,11302170,and 11472212)the Fundamental Research Funds for the Central Universities(No.3102014JCQ01079)
文摘The stochastic response of a noisy system with non-negative restoring force is investigated. The generalized cell mapping （GCM） method compute the transient and stationary probability density functions （PDFs） real-power is used to Combined with the global properties of the noise-free system, the evolutionary process of the tran- sient PDFs is revealed. The results show that stochastic P-bifurcation occurs when the system parameter varies in the response analysis and the stationary PDF evolves from bimodal to unimodal along the unstable manifold during the bifurcation.
基金supported by the National Natural Science Foundation of China(Nos.61735011,61675152 and 61505139)National Instrumentation Program of China(No.2013YQ030915)China Postdoctoral Science Foundation(No.2016M590200)
文摘A multi-channel synchronous demodulation system of a polarized low-coherence interferometer(PLCI)based on a matrix charge-coupled-device(CCD)is proposed and demonstrated.By using special designs,the system allows the signals from different channels to be received and demodulated synchronously.Multichannel air pressure experiments were implemented to verify the effectiveness of the proposed system.The experiment results showed that the Fabry–Perot(F–P)sensors could be demodulated synchronously with a high tolerance for light sources and sensors,which indicated that any sensor and light source that can be demodulated by PLCI were allowed to be employed,leading to a wide application in the field of multichannel synchronous measurement.
基金National Key Scientific Instrument and Equipment Development Project of China(2013YQ03091502)National Natural Science Foundation of China(NSFC)(61378043,61107035)
文摘A novel magnetic field sensing system based on the fiber loop ring-down technique is proposed in this paper. In the fiber loop, a U-bent single-mode-fiber structure coated with magnetic fluid(MF) serves as the sensing head, and an erbium-doped fiber amplifier(EDFA) is introduced to compensate for the intrinsic loss of the cavity. The ring-down time of the system varies with the change of applied magnetic field due to the tunable absorption coefficient and refractive index of the MF. Therefore, measurement of the magnetic field can be realized by monitoring the ringdown time. The experimental results show that the performance of the system is extremely dependent on the interrogation wavelength, because both the gain of the EDFA and the loss of the sensing head are wavelength dependent.We found that at the optimal wavelength, the ratio of the gain to loss attained its maximum. The sensing system was experimentally demonstrated and a sensitivity of-0.5951 μs∕Oe was achieved.
基金the National Natural Science Foundation of China(Grant No.11104200)the Natural Science Foundation of Tianjin(No.18JCYBJC17000).
文摘Electromagnetically induced transparency(EIT)phenomenon is observed in simple metamaterial which consists of concentric double U-shaped resonators(USRs).The numerical and theoretical analysis reveals that EIT arises from the bright-bright mode coupling.The transmission spectra at different polarization angle of incident light shows that EIT transparency window is polarization sensitive.More interestingly,Fano resonance appears in the transmission spectrum at certain polarization angles.The sharp and asymmetric Fano lineshape is high valuable for sensing.The performance of sensor is investigated and the sensitivity is high up to 327 GHz/RIU.Furthermore,active control of EIT window is realized by incorporating photosensitive silicon.The proposed USR structure is simple and compact,which may find significant applications in tunable integrated devices such as biosensor,filters,and THz modulators.
基金partially supported by the Natural Science Foundation of Tianjin under grant 13JCYBJC16100the National Natural Science Foundation of China under grants 61107035 and 61378043+1 种基金the National Key Scientific Instrument and Equipment Development Project of China under grant 2013YQ03091502the National Basic Research Program of China(973 Program)under grant 2014CB340104
文摘In this paper, Er/Yb co-doped fiber amplifiers(EYDFAs) with an Yb-band fiber Bragg grating(FBG) at the pump end to improve the performance of the amplifier is systematically studied. The influence of the reflectivity and center wavelength of the FBG along with the gain-fiber length on the performance of an EYDFA are numerically analyzed. The results show that the wavelength of the FBG has critical influence on the efficiency of the EYDFA,whereas the requirement to its reflectivity is relaxed. It is an effective and promising way to improve the efficiency of a high-power pumped EYDFA by introducing a suitable Yb-band FBG at the pump end. Based on the analysis of the underlying principles, suggestions for the practical design and possible further improvement strategies are also proposed.
