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Surface Acoustic Wave Humidity Sensors Based on(1120) ZnO Piezoelectric Films Sputtered on R-Sapphire Substrates 被引量:3
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作者 王艳 张淑仪 +2 位作者 范理 水修基 杨跃涛 《Chinese Physics Letters》 SCIE CAS CSCD 2015年第8期123-126,共4页
ZnO films on R-sapphire substrates are prepared and characterized by x-ray diffraction and scanning electron microscopy, which indicate that the thin films are well crystallized with (1120) texture. Love wave and Ra... ZnO films on R-sapphire substrates are prepared and characterized by x-ray diffraction and scanning electron microscopy, which indicate that the thin films are well crystallized with (1120) texture. Love wave and Rayleigh wave are used for fabrications of humidity sensors, which are excited in [1100] and [0001] directions of the (1120) ZnO piezoelectric films, respectively. The experimental results show that both kinds of sensors have good humidity response and repeatability, and the performances of the Love wave sensors are better than those of the Rayleigh wave sensors at room temperature. Moreover, the theoretical calculations of the mass sensitivity of the sensors are a/so carried out and the calculated results are in good agreement with the experimental measurements. 展开更多
关键词 ZnO Piezoelectric Films Sputtered on R-Sapphire Substrates Surface Acoustic wave Humidity Sensors based on
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Satellite-based RAR performance simulation for measuring directional ocean wave spectrum based on SAR inversion spectrum 被引量:2
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作者 REN Lin MAO Zhihua +1 位作者 HUANG Haiqing GONG Fang 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2010年第4期13-20,共8页
Some missions have been carried out to measure wave directional spectrum by synthetic aperture radar (SAR) and airborne real aperture radar (RAR) at a low incidence.Both them have their own advantages and limitati... Some missions have been carried out to measure wave directional spectrum by synthetic aperture radar (SAR) and airborne real aperture radar (RAR) at a low incidence.Both them have their own advantages and limitations.Scientists hope that SAR and satellite-based RAR can complement each other for the research on wave properties in the future.For this study,the authors aim to simulate the satellite-based RAR system to validate performance for measuring the directional wave spectrum.The principal measurements are introduced and the simulation methods based on the one developed by Hauser are adopted and slightly modified.To enhance the authenticity of input spectrum and the wave spectrum measuring consistency for SAR and satellite-based RAR,the wave height spectrum inversed from Envisat ASAR data by cross spectrum technology is used as the input spectrum of the simulation system.In the process of simulation,the sea surface,backscattering signal,modulation spectrum and the estimated wave height spectrum are simulated in each look direction.Directional wave spectrum are measured based on the simulated observations from 0 ? to 360 ? .From the estimated wave spectrum,it has an 180 ? ambiguity like SAR,but it has no special high wave number cut off in all the direction.Finally,the estimated spectrum is compared with the input one in terms of the dominant wave wavelength,direction and SWH and the results are promising.The simulation shows that satellite-based RAR should be capable of measuring the directional wave properties.Moreover,it indicates satellite-based RAR basically can measure waves that SAR can measure. 展开更多
关键词 satellite-based RAR directional wave spectrum SAR inversion performance simulation
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Distance-Coefficient-Based Imaging Accuracy Improving Method Based on the Lamb Wave 被引量:1
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作者 Shao-Jie Chen Shao-Ping Zhou +2 位作者 Yong Li Yan-Xun Xiang Min-Xin Qi 《Chinese Physics Letters》 SCIE CAS CSCD 2017年第4期55-59,共5页
An imaging accuracy improving method is established, within which a distance coefficient including location information between sparse array configuration and the location of defect is proposed to select higher signal... An imaging accuracy improving method is established, within which a distance coefficient including location information between sparse array configuration and the location of defect is proposed to select higher signal- to-noise ratio data from all experimental data and then to use these selected data for elliptical imaging. Tile relationships among imaging accuracy, distance coefficient and residual direct wave are investigated, and then the residual direct wave is introduced to make the engineering application more convenient. The effectiveness of the proposed method is evaluated experimentally by sparse transducer array of a rectangle, and the results reveal that selecting experimental data of smaller distance coefficient can effectively improve imaging accuracy. Moreover, the direct wave difference increases with the decrease of the distance coefficient, which implies that the imaging accuracy can be effectively improved by using the experimental data of the larger direct wave difference. 展开更多
关键词 Distance-Coefficient-based Imaging Accuracy Improving Method based on the Lamb wave
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A Transmission-Type Electrically Tunable Polarizer Based on Graphene Ribbons at Terahertz Wave Band 被引量:1
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作者 唐祎程 朱志宏 +4 位作者 张检发 郭楚才 刘肯 袁晓东 秦石乔 《Chinese Physics Letters》 SCIE CAS CSCD 2015年第2期91-94,共4页
We theoretically and numerically demonstrate that a transmission-type electrically tunable polarizer can be realized by using graphene ribbons supported on a dielectric film with a graphene sheet behind. The polarizat... We theoretically and numerically demonstrate that a transmission-type electrically tunable polarizer can be realized by using graphene ribbons supported on a dielectric film with a graphene sheet behind. The polarization mechanism originates from the antenna plasmon resonance of graphene stripes. The results of full-wave numerical simulations reveal that transmittance of 0.70 for one polarization and 0.0073 for another polarization can be obtained at normal incidence. The transmission-type electrically tunable polarizer provides and facilitates a variety of applications, including filtering, detecting, and imaging. 展开更多
关键词 THz A Transmission-Type Electrically Tunable Polarizer based on Graphene Ribbons at Terahertz wave Band
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Global Statistical Study of Ionospheric Waves Based on COSMIC GPS Radio Occultation Data
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作者 Xuan-Yun Zeng Xiang-Hui Xue +4 位作者 Xin-An Yue Ming-Jiao Jia Bing-Kun Yu ian-Fei Wu Chao Yu 《Chinese Physics Letters》 SCIE CAS CSCD 2018年第10期93-97,共5页
Extracting and parameterizing ionospheric waves globally and statistically is a longstanding problem. Based on the multichannel maximum entropy method(MMEM) used for studying ionospheric waves by previous work, we c... Extracting and parameterizing ionospheric waves globally and statistically is a longstanding problem. Based on the multichannel maximum entropy method(MMEM) used for studying ionospheric waves by previous work, we calculate the parameters of ionospheric waves by applying the MMEM to numerously temporally approximate and spatially close global-positioning-system radio occultation total electron content profile triples provided by the unique clustered satellites flight between years 2006 and 2007 right after the constellation observing system for meteorology, ionosphere, and climate(COSMIC) mission launch. The results show that the amplitude of ionospheric waves increases at the low and high latitudes(~0.15 TECU) and decreases in the mid-latitudes(~0.05 TECU). The vertical wavelength of the ionospheric waves increases in the mid-latitudes(e.g., ~50 km at altitudes of 200–250 km) and decreases at the low and high latitudes(e.g., ~35 km at altitudes of 200–250 km).The horizontal wavelength shows a similar result(e.g., ~1400 km in the mid-latitudes and ~800 km at the low and high latitudes). 展开更多
关键词 COSMIC Global Statistical Study of Ionospheric waves based on COSMIC GPS Radio Occultation Data GPS
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Analysis of Runoff in Ungauged Mountain Watersheds in Sichuan,China using Kinematic-wave-based GIUH Model 被引量:5
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作者 CAO Shuyou LEE Kwan Tun +3 位作者 HO Juiyi LIU Xingnian HUANG Er YANG Kejun 《Journal of Mountain Science》 SCIE CSCD 2010年第2期157-166,共10页
Floods are one of the most common natural hazards occurring all around the world.However,the knowledge of the origins of a food and its possible magnitude in a given region remains unclear yet.This lack of understandi... Floods are one of the most common natural hazards occurring all around the world.However,the knowledge of the origins of a food and its possible magnitude in a given region remains unclear yet.This lack of understanding is particularly acute in mountainous regions with large degrees in Sichuan Province,China,where runoff is seldom measured.The nature of streamflow in a region is related to the time and spatial distribution of rainfall quantity and watershed geomorphology.The geomorphologic characteristics are the channel network and surrounding landscape which transform the rainfall input into an output hydrograph at the outlet of the watershed.With the given geomorphologic properties of the watershed,theoretically the hydrological response function can be determined hydraulically without using any recorded data of past rainfall or runoff events.In this study,a kinematic-wave-based geomorphologic instantaneous unit hydrograph (KW-GIUH) model was adopted and verified to estimate runoff in ungauged areas.Two mountain watersheds,the Yingjing River watershed and Tianquan River watershed in Sichuan were selected as study sites.The geomorphologic factors of the two watersheds were obtained by using a digital elevation model (DEM) based on the topographic database obtained from the Shuttle Radar Topography Mission of US's NASA.The tests of the model on the two watersheds were performed both at gauged and ungauged sites.Comparison between the simulated and observed hydrographs for a number of rainstorms at the gauged sites indicated the potential of the KW-GIUH model as a useful tool for runoff analysis in these regions.Moreover,to simulate possible concentrated rainstorms that could result in serious flooding in these areas,synthetic rainfall hyetographs were adopted as input to the KW-GIUH model to obtain the flow hydrographs at two ungauged sites for different return period conditions.Hydroeconomic analysis can be performed in the future to select the optimum design return period for determining the flood control work. 展开更多
关键词 Kinematic-wave-based geomorphologic instantaneous unit hydrograph (KW-GIUH) Ungauged watershed Rainfall-runoff simulation Digital elevation model
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Response Analysis of Tension-Based Tension Leg Platform Under Irregular Waves 被引量:1
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作者 D.S.Bhaskara Rao R.Panneer Selvam 《China Ocean Engineering》 SCIE EI CSCD 2016年第4期603-614,共12页
Tension Leg Platform(TLP) is a hybrid structure used as oil drilling and production facility within water depths of 1200 m. The extension of this TLP concept to deeper waters is a challenge and warrants for some inn... Tension Leg Platform(TLP) is a hybrid structure used as oil drilling and production facility within water depths of 1200 m. The extension of this TLP concept to deeper waters is a challenge and warrants for some innovative design concepts. In this paper, a relatively new concept of TLP which is christened as Tension-Based Tension Leg Platform(TBTLP) and patented by Srinivasan(1998) has been chosen for study. Response analysis of TLP with one tension base under irregular waves for three different sea states has been performed using hydrodynamic tool ANSYS? AQWA?. Results are reported in terms of RAOs, response spectrums for surge, heave and pitch degrees of freedom from which spectral statistics have been obtained. The statistics of TBTLP have been compared with TLPs(without tension base) for two different water depths to highlight the features of the new concept. The effect of viscous damping and loading effects on the RAOs are also investigated. 展开更多
关键词 Tension-based Tension Leg Platform irregular waves time domain response response amplitudeoperators SPECTRUM STATISTICS coupled analysis
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High-Frequency Guided Wave Scattering by a Partly Through-Thickness Hole Based on 3D Theory
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作者 张海燕 徐建 马世伟 《Chinese Physics Letters》 SCIE CAS CSCD 2015年第8期94-97,共4页
We present a theoretical investigation of the scattering of high frequency S0 Lamb mode from a circular blind hole defect in a plate based on the 3D theory. The SO wave is incident at the frequency above the A1 mode c... We present a theoretical investigation of the scattering of high frequency S0 Lamb mode from a circular blind hole defect in a plate based on the 3D theory. The SO wave is incident at the frequency above the A1 mode cut-off frequency, in which the popular approximate plate theories are inapplicable. Due to the non-symmetric blind hole defect, the scattered fields will contain higher order converted modes in addition to the fundamental SO and AO modes. The far-field scattering amplitudes of various propagating Lamb modes for different hole sizes are inspected. The results are compared with those of lower frequencies and some different phenomena are found. Two-dimensional Fourier transform (2DFT) results of transient scattered Lamb and SH wave signals agree well with the analytical dispersion curves, which check the validity of the solutions from another point of view. 展开更多
关键词 High-Frequency Guided wave Scattering by a Partly Through-Thickness Hole based on 3D Theory
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Microwave photonic notch filter with complex coefficient based on four wave mixing
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作者 许东 曹晔 +1 位作者 童峥嵘 杨菁芃 《Optoelectronics Letters》 EI 2016年第6期417-420,共4页
A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing(FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber(HNLF), and mu... A microwave photonic notch filter with a complex coefficient is proposed and demonstrated based on four wave mixing(FWM). FWM effect of two single-frequency laser beams occurs in a highly nonlinear fiber(HNLF), and multi-wavelength optical signals are generated and used to generate the multi-tap of microwave photonic filter(MPF). The complex coefficient is generated by using a Fourier-domain optical processor(FD-OP) to control the amplitude and phase of the optical carrier and phase modulation sidebands. The results show that this filter can be changed from bandpass filter to notch filter by controlling the FD-OP. The center frequency of the notch filter can be continuously tuned from 5.853 GHz to 29.311 GHz with free spectral range(FSR) of 11.729 GHz. The shape of the frequency response keeps unchanged when the phase is tuned. 展开更多
关键词 notch photonic mixing tuned processor microwave unchanged continuously tunable modulator
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Design of a Broadband E-Plane Power Combiner Based on Quarter-Arc Bent Rectangular Waveguides for Sub-THz and THz Wave
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作者 唐效频 杨梓强 +1 位作者 史宗君 兰峰 《Chinese Physics Letters》 SCIE CAS CSCD 2016年第8期135-138,共4页
A method of designing an E-plane power combiner composed of two quarter-arc bent rectangular waveguides is proposed for sub-THz and THz waves. The quarter-arc bent-waveguide power combiner has a simple geometry which ... A method of designing an E-plane power combiner composed of two quarter-arc bent rectangular waveguides is proposed for sub-THz and THz waves. The quarter-arc bent-waveguide power combiner has a simple geometry which is easy to design and fabricate. By HFSS codes, the physical mechanism and performance of the power combiner are analyzed, and the relationship between the output characteristics and the structure/operating parameters is given. Simulation results show that our power combiner is suitable for the combining of two equalpower and reversed-phase signals, the bandwidth of the combiner is wide and can be adjusted by the radius of the quarter-arc, and the isolation performance of the combiner can be improved by adding thin film resistive septa at the junction of two quarter-arc bent waveguides. Meanwhile, an approximate method based on the analytic geometrical analysis is given to design this power combiner for different frequency bands. 展开更多
关键词 of in is THZ Design of a Broadband E-Plane Power Combiner based on Quarter-Arc Bent Rectangular waveguides for Sub-THz and THz wave for on
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Hydrodynamic Simulation of Wave Energy Converter Using Particle-Based Computational Fluid Dynamics 被引量:1
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作者 Yodchai Tiaple 《Journal of Marine Science and Application》 CSCD 2019年第1期48-53,共6页
Wave energy from the ocean is currently a very popular renewable energy, and its development has primarily focused on the shape of the wave energy converter(WEC) used to efficiently convert wave energy into electrical... Wave energy from the ocean is currently a very popular renewable energy, and its development has primarily focused on the shape of the wave energy converter(WEC) used to efficiently convert wave energy into electrical energy. However, the free surface ocean wave problem is very complex and the parameters affecting WEC behavior are difficult to understand. In this paper, based on the Lattice-Boltzmann method, we present particle-based CFD simulation results for the pivoted-type WEC that exhibits both vertical and horizontal motions. In this method, the computation domain need not be a mesh and complex geometry is not a limiting factor. Using a free-surface turbulence model, we simulated the fluid-structure interaction. We detail our simulation results, which show good agreement with those in the literature. 展开更多
关键词 wave energy converter Pivoted BUOY LATTICE-BOLTZMANN Particle-based CFD
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植物型生态护岸消浪数值模型构建及物理试验研究
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作者 白洋 段明涛 +3 位作者 柳叶 秦梦春 李绍武 赵帅 《海洋工程》 北大核心 2026年第1期118-128,共11页
植物型生态护岸作为一种新兴的海岸防护方式,不仅具备护岸功能,还能有效促进海岸带生态修复。然而,如何构建植物型生态护岸并对其消浪效果进行定量评估,仍是一个有待解决的问题。因此,采用数值模型模拟和物理模型试验两种方法对其进行... 植物型生态护岸作为一种新兴的海岸防护方式,不仅具备护岸功能,还能有效促进海岸带生态修复。然而,如何构建植物型生态护岸并对其消浪效果进行定量评估,仍是一个有待解决的问题。因此,采用数值模型模拟和物理模型试验两种方法对其进行了研究。通过在Navier-Stokes方程中引入植物与流体作用项,采用标准Smagorinsky紊流模式描述植物与波浪作用的紊流效应,并改进MAC算法(marker-and-cell method)和波浪表面追踪法,开发了数值模型;通过物理模型试验验证了数值模型,构建了植物消浪阻力系数经验公式。研究结果表明:构建的数值模型可以反映植物的消浪效果,量化海岸植物的消浪和透浪特性;植物消浪阻力系数经验公式可以反映植物的物理特性。研究工作可为植物型生态海岸防护工程设计提供科学依据。 展开更多
关键词 海岸防护结构 植物型生态护岸 波浪数值模型 MAC算法
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关闭/废弃矿井采空区反射无线电波勘探方法及应用
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作者 庞瑶 吴荣新 +1 位作者 王锦国 胡泽安 《煤田地质与勘探》 北大核心 2026年第2期214-225,共12页
【目的和方法】关闭/废弃矿井数量庞大,重新开发和利用关闭/废弃矿井具有重大研究意义及生产价值。我国关闭/废弃矿井能源、空间资源的二次开发和利用起步较晚,基础理论和关键技术研究相对薄弱。为研究关闭/废弃矿井采空破坏区地下空间... 【目的和方法】关闭/废弃矿井数量庞大,重新开发和利用关闭/废弃矿井具有重大研究意义及生产价值。我国关闭/废弃矿井能源、空间资源的二次开发和利用起步较晚,基础理论和关键技术研究相对薄弱。为研究关闭/废弃矿井采空破坏区地下空间发育特征,提出一种基于反射无线电波的关闭/废弃矿井采空区勘探方法,在关闭/废弃矿井工作面上/下方或两侧岩石巷道中,布设同源检距观测系统的反射无线电波勘探施工。构建三维层状地电数值模型,模拟并分析均匀采空破坏区和含水/瓦斯采空破坏区条件下,多频率和多源检距的反射无线电波响应特征。【结果和结论】采空破坏区均匀介质中反射无线电波场图像呈直线状,含水/瓦斯异常构造时,其会削弱/增强反射波信号,反射无线电波接收磁场强度曲线呈“凹”/“凸”状。开展了地下隧道物理相似模拟试验,模拟实验结果分为明显的五段,与隧道真实地质条件相符,验证了反射无线电波勘探方法的有效性。结合已有经验,在关闭/废弃矿井工作面展开了反射无线电波探测实验并获取数据,实验结果准确反映了9号煤中异常区可能存在的地质异常,与回采调查资料及钻探结果一致,取得了较好的应用效果。利用反射无线电波探测矿井采空区及异常体的可行性得到了验证,为关闭/废弃矿井地下空间探查提供了一个新方法。 展开更多
关键词 关闭/废弃矿井 无线电波勘探 反射无线电波 采空区 多频
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声触诊组织量化技术联合其他指标诊断慢性乙型肝炎患者肝纤维化效能临床研究
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作者 张卉新 隋雪梅 《实用肝脏病杂志》 2026年第2期191-194,共4页
目的探讨超声声触诊组织量化技术检测剪切波速度(SWV)联合其他指标诊断慢性乙型肝炎(CHB)患者显著性肝纤维化的应用价值。方法2023年6月~2025年6月我院诊断的CHB患者97例,均行肝穿刺活检,使用超声声触诊组织量化检测SWV,同时检测血清和... 目的探讨超声声触诊组织量化技术检测剪切波速度(SWV)联合其他指标诊断慢性乙型肝炎(CHB)患者显著性肝纤维化的应用价值。方法2023年6月~2025年6月我院诊断的CHB患者97例,均行肝穿刺活检,使用超声声触诊组织量化检测SWV,同时检测血清和血液学指标,计算天冬氨酸氨基转移酶/血小板比值指数(APRI)和纤维化4因子指数(FIB-4),常规检测血清透明质酸(HA)水平,应用受试者工作特征(ROC)曲线分析指标联合诊断显著性肝纤维化的效能。结果50例显著性肝纤维化组年龄、血清ALT和AST水平均显著高于或大于,而外周血血小板计数显著低于47例非显著性肝纤维化组(P<0.05);显著性肝纤维化组SWV、APRI、FIB-4和血清HA水平分别为(2.1±0.4)m/s、(1.2±0.7)、(2.0±1.0)和132.2(95.4,210.5)ng/ml,均显著高于非显著性肝纤维化组[分别为(1.3±0.3)m/s、(0.6±0.3)、(1.0±0.4)和55.2(38.4,72.6)ng/ml,P<0.05];以SWV联合其他任一指标诊断显著性肝纤维化的AUC为0.94(95%CI:0.90~0.97),其敏感度为91.5%,特异度为86.0%。结论采取超声声触诊组织量化技术检测SWV再联合任一常用的肝纤维化指标可帮助临床医生筛查CHB患者肝纤维化程度,以便及时采取进一步的诊断和干预措施。 展开更多
关键词 慢性乙型肝炎 声触诊组织量化技术 剪切波速度 天冬氨酸氨基转移酶/血小板比值指数 纤维化4因子指数 透明质酸 诊断
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矩形液舱横波与法拉第波共振的数值模拟
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作者 谭志荣 赵修叁 +1 位作者 朱汉华 王斌 《舰船科学技术》 北大核心 2026年第1期19-26,共8页
为研究液舱受不同自由度方向激励下的晃荡行为,以矩形液舱为研究对象,开展了横波和法拉第纵波激励下的晃荡研究。为此建立了基于计算流体力学的数值模型,依次分析了液舱在围绕一阶共振的系列横波激励及3种不稳定模式的纵波频率下波面幅... 为研究液舱受不同自由度方向激励下的晃荡行为,以矩形液舱为研究对象,开展了横波和法拉第纵波激励下的晃荡研究。为此建立了基于计算流体力学的数值模型,依次分析了液舱在围绕一阶共振的系列横波激励及3种不稳定模式的纵波频率下波面幅值与舱壁压强的变化特点,并进行时-频域的综合分析。结果显示,随着横波激励接近晃荡中心,非线性作用愈加显著,压力频谱向低阶自耦区转移并参与更多非线性效应。而对于纵波激励,液舱对谐波和超谐波激励不敏感,在法拉第次谐波激励下,液舱随时间累积产生强烈晃荡,并激发出一阶模态的主参数晃荡。在主参数晃荡的影响下,二阶压力频谱在自耦合区表现出强烈的非线性特征,并叠加生成了四阶频的成分。 展开更多
关键词 矩形液舱 法拉第波 一阶横波共振 Morlet小波变换 小波二阶相干谱
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基于聚氨酯阻尼结构的电机机座轻量化低振动一体化设计
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作者 龚京风 熊德辉 +2 位作者 宣领宽 张跃 马俊洋 《噪声与振动控制》 北大核心 2026年第1期90-94,100,共6页
综合考虑电机轻量化和减振降噪具有重要意义,为此基于聚氨酯阻尼结构,提出针对电机机座轻量化、低振动的一体化设计方法。以一台Y80M1-2鼠笼式三相异步电机为研究对象,通过在机座圆柱壳和机脚处开孔实现减重30.42%,在圆柱壳孔内嵌聚氨... 综合考虑电机轻量化和减振降噪具有重要意义,为此基于聚氨酯阻尼结构,提出针对电机机座轻量化、低振动的一体化设计方法。以一台Y80M1-2鼠笼式三相异步电机为研究对象,通过在机座圆柱壳和机脚处开孔实现减重30.42%,在圆柱壳孔内嵌聚氨酯阻尼材料实现低振动。利用磁固耦合仿真技术,分别建立蜂窝形、矩形、空心扇形3种开孔形式的轻量化、低振动电机机座,对比分析不同开孔形式对电机机脚垂向振动响应的影响。结果表明,轻量化、低振动机座设计在整体频带上能有效降低振动,其中空心扇形机座的机脚振动加速度总级最低。采用3D金属打印技术等比例制作满足结构强度要求的空心扇形机座,并通过试验验证其减振效果。 展开更多
关键词 振动与波 电机机座 异步电机 聚氨酯阻尼材料 轻量化 振动控制
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中老年人估计脉搏波速度动态变化轨迹及其与心血管疾病的关系
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作者 黄明亮 马秋平 《护理研究》 北大核心 2026年第4期542-548,共7页
目的:探讨社区中老年人估计脉搏波速度动态变化轨迹及其与心血管疾病的关系。方法:基于中国健康与养老追踪调查(CHARLS)的队列数据,收集人群一般资料及实验室指标。采用群组轨迹模型(GBTM)构建社区中老年人估计脉搏波速度动态变化的异... 目的:探讨社区中老年人估计脉搏波速度动态变化轨迹及其与心血管疾病的关系。方法:基于中国健康与养老追踪调查(CHARLS)的队列数据,收集人群一般资料及实验室指标。采用群组轨迹模型(GBTM)构建社区中老年人估计脉搏波速度动态变化的异质性轨迹,应用Logistic回归分析探讨估计脉搏波速度动态变化轨迹与心血管疾病的关系。结果:共5 933名参与者纳入分析,其中发生心血管疾病1 112例(18.7%)。群组轨迹模型分析显示,存在4种估计脉搏波速度变化轨迹:低水平稳定组(30.0%)、中水平上升组(39.6%)、上升后平稳组(23.0%)和高水平上升组(7.4%)。Logistic回归分析显示,校正混杂因素后,相对于低水平稳定组,中水平上升组、上升后平稳组和高水平上升组心血管疾病的发生风险明显增加。结论:社区中老年人的估计脉搏波速度变化轨迹存在群体异质性,较高的估计脉搏波速度轨迹与心血管疾病的发生相关。提示医务人员应重视中老年人的估计脉搏波速度变化,并根据不同轨迹制定对应干预策略。 展开更多
关键词 中老年人 估计脉搏波速度 心血管疾病 群组轨迹模型
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Research of the Unity Theory Between Three-level Space Vector and Carrier-based PWM Modulation Strategy 被引量:28
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作者 CHEN Juan HE Yingjie WANG Xinyu LIU Jinjun 《中国电机工程学报》 EI CSCD 北大核心 2013年第9期I0010-I0010,共1页
两电平空间矢量脉宽调制(space vector pulse widthmodulation,SVPWM)与正弦脉宽调制(sinusoidal pulse widthmodulation,SPWM)存有一定的本质关系,对于三电平,在常见的8段式SVPWM序列中可以证明,SVPWM与SPWM本质上也存在某种统一... 两电平空间矢量脉宽调制(space vector pulse widthmodulation,SVPWM)与正弦脉宽调制(sinusoidal pulse widthmodulation,SPWM)存有一定的本质关系,对于三电平,在常见的8段式SVPWM序列中可以证明,SVPWM与SPWM本质上也存在某种统一。实际的SVPWM调制中,由于要考虑中点电压平衡、减少谐波等其它性能问题,一般会利用开关冗余状态得到8段以上的开关调制序列。目前的文献中还未曾有对这些情况进行统一性地验证,因此三电平SVPWM与SPWM的统一理论存在一定的不足。研究发现,可通过严格地理论推导将传统意义上的调制波分解为2个子调制波,再进行SPWM调制,可以得到与SVPWM完全吻合的序列。该文在此方法基础上深入研究了8段以上(10、12、14段)的SVPWM调制序列与SPWM的统一。经过严格地理论推导,成功实现了含任意段数的SVPWM序列与SPWM的统一。仿真结果证明了该理论的正确性。 展开更多
关键词 三电平逆变器 SVPWM 调制策略 统一理论 载波 矢量和 空间 研究人员
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Study on Nonlinear Characteristics of Freak-Wave Forces with Different Wave Steepness 被引量:1
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作者 DENG Yan-fei TIAN Xin-liang LI Xin 《China Ocean Engineering》 SCIE EI CSCD 2019年第5期608-617,共10页
The nonlinear wave forces on vertical cylinders induced by freak wave trains were experimentally investigated. A series of freak wave trains with different wave steepness were modeled in a wave flume. The correspondin... The nonlinear wave forces on vertical cylinders induced by freak wave trains were experimentally investigated. A series of freak wave trains with different wave steepness were modeled in a wave flume. The corresponding wave forces on vertical cylinders of different diameters were measured. The experimental wave forces were also compared with the predicted results based on Morison formula. Particular attentions were paid to the effects of wave steepness on the dimensionless peak forces, asymmetry characteristics of the impact forces and high-frequency force components. Wavelet-based analysis methods were employed in revealing the local energy structures and quadratic phase coupling in the freak wave forces. 展开更多
关键词 freak wave VERTICAL CYLINDER wave FORCE wavelet-based ANALYSIS
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The improved model of estimating global whitecap coverage based on satellite data 被引量:3
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作者 REN Danqin HUA Feng +1 位作者 YANG Yongzeng SUN Baonan 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2016年第5期66-72,共7页
The pro and con of whitecap parameterizations and a statistical wave breaking model are discussed. An improved model is derived by combining satellite-based parameterization and the wave breaking model. The appropriat... The pro and con of whitecap parameterizations and a statistical wave breaking model are discussed. An improved model is derived by combining satellite-based parameterization and the wave breaking model. The appropriate constants for the general wave state are obtained by considering the breaking condition of the wave slope and fitting with the satellite-based parameterization. The result is close to the constants based on the whitecap data from Monahan. Comparing with satellite-based data and the original model's results, the improved model's results are consistent with satellite-based data and previous studies. The global seasonal distributions of the whitecap coverage averaged from 1998 to 2008 are presented. Spatial and seasonal features of the whitecap coverage are analyzed. 展开更多
关键词 whitecap coverage statistical wave breaking model satellite-based parameterization
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