With the rapid advancement of the intelligent era, intelligent electromagnetic interference (EMI) shielding devices are receiving more and more attention due to their advantages in environmental self-adaption response...With the rapid advancement of the intelligent era, intelligent electromagnetic interference (EMI) shielding devices are receiving more and more attention due to their advantages in environmental self-adaption response. Accordingly, appropriate EMI shielding materials are crucial to blocking harmful electromagnetic radiation and passing serviceable electromagnetic waves. Smart EMI shielding materials that can dynamically adjust their EMI shielding effectiveness (SE) in response to specific application requirements and environmental changes are extremely advantageous in both military and civil areas. To date, materials with adjustable EMI SE for various responses have been developed. This review pays special attention to smart materials with tunable EMI SE. The design strategies, mechanism and recent progress of smart EMI shielding materials are discussed together with different stimuli responses, including compression strain, tensile strain, chemical reagent, shape memory, phase transition and crossover angle change-induced responses. The review ends up to discuss challenges and perspectives for smart EMI shielding materials.展开更多
Most previous investigations on interference effects of tall buildings under wind actions focused on the wind induced interference effects between two buildings,and the interference effects of three or more buildings ...Most previous investigations on interference effects of tall buildings under wind actions focused on the wind induced interference effects between two buildings,and the interference effects of three or more buildings have seldom been studied so far due to the huge workload involved in experiments and data processing.In this paper,mean and dynamic force/response interference effects and peak wind pressure interference effects of two and three tall buildings,especially the three-building configuration,are investigated through a series of wind tunnel tests on typical tall building models using high frequency force balance technique and wind pressure measurements.Furthermore,the present paper focuses on the effects of parameters,including breadth ratio and height ratio of the buildings and terrain category,on the interference factors and derives relevant regression results for the interference factors.展开更多
The“riser group−fluid between risers”is taken as the carrier,and the experiment on vortex-induced vibration of tandem riser groups coupling interference effect under sensitive spacing is performed.The least-square m...The“riser group−fluid between risers”is taken as the carrier,and the experiment on vortex-induced vibration of tandem riser groups coupling interference effect under sensitive spacing is performed.The least-square method is used to linearly fit the reduced velocity and main frequency,and the rule of Strouhal numbers is analyzed.Each mode is separated based on the mode decomposition theory,and the mode conversion mechanism is also explored.The concept of“interference efficiency”is introduced to study the dynamic characteristics and response evolutions of different riser groups.The results show that the wake shielding effect widely exists in tandem riser groups,and the interference effect of midstream and downstream risers on their upstream risers is significantly lower than that of upstream risers on midstream and downstream risers.The trajectories of midstream and downstream risers lag behind their upstream risers due to multiple shadowing effects,the vibration frequency range of downstream riser is widened and the dominant frequency is extremely unstable.Compared with the isolated riser,wake interference suppresses the vibration dis-placement of the midstream and downstream risers in the in-line direction,and enhances the displacement of upstream and midstream risers in the cross-flow direction.The interference effect of the fluid between risers at low velocities is stronger than that at higher velocities,and the cross-flow displacements of upstream risers are always in the interference enhancement region.It is urgent to pay attention to the cross-flow displacement of upstream and midstream risers in tandem riser groups considering the safety design.展开更多
In this paper, the temporal and spatial patterns of a diffusive predator-prey model with mutual interference under homogeneous Neumann boundary conditions were studied. Specifically, first, taking the intrinsic growth...In this paper, the temporal and spatial patterns of a diffusive predator-prey model with mutual interference under homogeneous Neumann boundary conditions were studied. Specifically, first, taking the intrinsic growth rate of the predator as the parameter, we give a computational and theoretical analysis of Hopf bifurcation on the positive equilibrium for the ODE system. As well, we have discussed the conditions for determining the bifurcation direction and the stability of the bifurcating periodic solutions.展开更多
For anti-jamming and anti-countermeasure techniques of the sonar receiver,the response characteristics of the automatic gain control(AGC)circuit and the survivability of the prime circuit under strong interference are...For anti-jamming and anti-countermeasure techniques of the sonar receiver,the response characteristics of the automatic gain control(AGC)circuit and the survivability of the prime circuit under strong interference are analyzed by simulations and experiments.An AGC simulation model based on the voltage control amplifier VCA810 prototype is proposed.Then static and dynamic simulations are realized with single frequency signal and linear frequency modulated(LFM)signal commonly used in the active sonar.Based on intense sound pulse(ISP)interference experiments,the real-time response characteristics of each module of the receiver are studied to verify the correctness of the model as well as the simulation results.Simulation and experiment results show that,under 252 dB/20μs ISP interference,the specific sonar receiver will produce sustained cut top oscillation above 30 ms,which may affect the receiver and block the regular sonar signal.展开更多
针对舰船辐射噪声低频线谱动态频率精细特征提取存在的频率分辨率低、瞬时频率跟踪性差、频率分析不够精细等问题,提出了一种基于移频频率细化瞬时自相关函数滤波的改进维格纳威利分布(Wigner Ville distribution,WVD)算法Z-FIR-WVD(zoo...针对舰船辐射噪声低频线谱动态频率精细特征提取存在的频率分辨率低、瞬时频率跟踪性差、频率分析不够精细等问题,提出了一种基于移频频率细化瞬时自相关函数滤波的改进维格纳威利分布(Wigner Ville distribution,WVD)算法Z-FIR-WVD(zoom-finite impulse response filter-WVD)。通过对移频降采样瞬时自相关函数在时域进行FIR(finite impulse response)滤波后的信号进行细化分析,可有效提高对WVD中多线谱交叉项干扰的抑制能力和频率分辨能力,实现对低频线谱动态精细特征的有效提取。仿真实验和实测信号验证结果表明,该算法在保持WVD频率聚集性的前提下,可有效抑制交叉项干扰,并实现对低频线谱的高频率分辨率动态分析,为舰船辐射噪声低频线谱动态频率精细特征提取问题提供了一种新的解决方法。展开更多
地震振幅变化是时移地震分析中非常重要的研究内容,但是影响地震振幅变化的因素比较复杂,由于薄层干涉效应,薄地层的厚度也会对地震反射振幅产生影响。为了量化分析储层厚度对时移地震反射振幅差异的影响,以渤海湾盆地某浅层疏松砂岩油...地震振幅变化是时移地震分析中非常重要的研究内容,但是影响地震振幅变化的因素比较复杂,由于薄层干涉效应,薄地层的厚度也会对地震反射振幅产生影响。为了量化分析储层厚度对时移地震反射振幅差异的影响,以渤海湾盆地某浅层疏松砂岩油藏为例,通过地震岩石物理建模、流体替换、地震正演模拟等技术手段构建时移地震正演数据,并进行时移地震振幅定量分析。结果显示:时移地震振幅差异受薄层干涉效应的影响非常明显,地层厚度小于λ/8(λ为地震波波长)时振幅差异变小,在λ/8到λ/2之间时振幅差异变大,达到λ/2之后振幅差异才是油藏开采活动的正常响应;地层厚度在λ/8到λ/2之间时,薄层干涉效应会将时移地震差异变大,对于时移地震观测是有利因素,对时移地震定量解释却容易产生误导;AVO(Amplitude Versus Offset)属性反演、地震反演技术也无法消除薄层干涉效应的影响。进行时移地震定量解释时一定不要忽视薄层造成的假象,建议利用技术手段消除地震振幅干涉效应之后再开展时移地震解释工作。展开更多
基金financially supported by the National Natural Science Foundation of China(No.52173264)the Natural Science Foundation Project of Chongqing(No.cstc2024ycjh-bgzxm0005).
文摘With the rapid advancement of the intelligent era, intelligent electromagnetic interference (EMI) shielding devices are receiving more and more attention due to their advantages in environmental self-adaption response. Accordingly, appropriate EMI shielding materials are crucial to blocking harmful electromagnetic radiation and passing serviceable electromagnetic waves. Smart EMI shielding materials that can dynamically adjust their EMI shielding effectiveness (SE) in response to specific application requirements and environmental changes are extremely advantageous in both military and civil areas. To date, materials with adjustable EMI SE for various responses have been developed. This review pays special attention to smart materials with tunable EMI SE. The design strategies, mechanism and recent progress of smart EMI shielding materials are discussed together with different stimuli responses, including compression strain, tensile strain, chemical reagent, shape memory, phase transition and crossover angle change-induced responses. The review ends up to discuss challenges and perspectives for smart EMI shielding materials.
基金supported by the National Natural Science Foundation of China (90715040)
文摘Most previous investigations on interference effects of tall buildings under wind actions focused on the wind induced interference effects between two buildings,and the interference effects of three or more buildings have seldom been studied so far due to the huge workload involved in experiments and data processing.In this paper,mean and dynamic force/response interference effects and peak wind pressure interference effects of two and three tall buildings,especially the three-building configuration,are investigated through a series of wind tunnel tests on typical tall building models using high frequency force balance technique and wind pressure measurements.Furthermore,the present paper focuses on the effects of parameters,including breadth ratio and height ratio of the buildings and terrain category,on the interference factors and derives relevant regression results for the interference factors.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.51709161 and U2006226)the Key Technology Research and Development Program of Shandong Province(Grant No.2019GHY112061)+1 种基金the Research and Innovation Team of Ocean Oil and Gas Development Engineering Structure,College of Civil Engineering and Architecture,Shandong University of Science and Technology(Grant No.2019TJKYTD01)the Natural Science Foundation of Shandong Province(Grant No.ZR2020ME261).
文摘The“riser group−fluid between risers”is taken as the carrier,and the experiment on vortex-induced vibration of tandem riser groups coupling interference effect under sensitive spacing is performed.The least-square method is used to linearly fit the reduced velocity and main frequency,and the rule of Strouhal numbers is analyzed.Each mode is separated based on the mode decomposition theory,and the mode conversion mechanism is also explored.The concept of“interference efficiency”is introduced to study the dynamic characteristics and response evolutions of different riser groups.The results show that the wake shielding effect widely exists in tandem riser groups,and the interference effect of midstream and downstream risers on their upstream risers is significantly lower than that of upstream risers on midstream and downstream risers.The trajectories of midstream and downstream risers lag behind their upstream risers due to multiple shadowing effects,the vibration frequency range of downstream riser is widened and the dominant frequency is extremely unstable.Compared with the isolated riser,wake interference suppresses the vibration dis-placement of the midstream and downstream risers in the in-line direction,and enhances the displacement of upstream and midstream risers in the cross-flow direction.The interference effect of the fluid between risers at low velocities is stronger than that at higher velocities,and the cross-flow displacements of upstream risers are always in the interference enhancement region.It is urgent to pay attention to the cross-flow displacement of upstream and midstream risers in tandem riser groups considering the safety design.
文摘In this paper, the temporal and spatial patterns of a diffusive predator-prey model with mutual interference under homogeneous Neumann boundary conditions were studied. Specifically, first, taking the intrinsic growth rate of the predator as the parameter, we give a computational and theoretical analysis of Hopf bifurcation on the positive equilibrium for the ODE system. As well, we have discussed the conditions for determining the bifurcation direction and the stability of the bifurcating periodic solutions.
基金supported by the National Natural Science Foundation of China(10974154)the National Innovation Project of China for Undergraduates(101069935)
文摘For anti-jamming and anti-countermeasure techniques of the sonar receiver,the response characteristics of the automatic gain control(AGC)circuit and the survivability of the prime circuit under strong interference are analyzed by simulations and experiments.An AGC simulation model based on the voltage control amplifier VCA810 prototype is proposed.Then static and dynamic simulations are realized with single frequency signal and linear frequency modulated(LFM)signal commonly used in the active sonar.Based on intense sound pulse(ISP)interference experiments,the real-time response characteristics of each module of the receiver are studied to verify the correctness of the model as well as the simulation results.Simulation and experiment results show that,under 252 dB/20μs ISP interference,the specific sonar receiver will produce sustained cut top oscillation above 30 ms,which may affect the receiver and block the regular sonar signal.
文摘地震振幅变化是时移地震分析中非常重要的研究内容,但是影响地震振幅变化的因素比较复杂,由于薄层干涉效应,薄地层的厚度也会对地震反射振幅产生影响。为了量化分析储层厚度对时移地震反射振幅差异的影响,以渤海湾盆地某浅层疏松砂岩油藏为例,通过地震岩石物理建模、流体替换、地震正演模拟等技术手段构建时移地震正演数据,并进行时移地震振幅定量分析。结果显示:时移地震振幅差异受薄层干涉效应的影响非常明显,地层厚度小于λ/8(λ为地震波波长)时振幅差异变小,在λ/8到λ/2之间时振幅差异变大,达到λ/2之后振幅差异才是油藏开采活动的正常响应;地层厚度在λ/8到λ/2之间时,薄层干涉效应会将时移地震差异变大,对于时移地震观测是有利因素,对时移地震定量解释却容易产生误导;AVO(Amplitude Versus Offset)属性反演、地震反演技术也无法消除薄层干涉效应的影响。进行时移地震定量解释时一定不要忽视薄层造成的假象,建议利用技术手段消除地震振幅干涉效应之后再开展时移地震解释工作。
