Driver at 10 MJ and 1 shot/30 min for inertial confinement fusion at high gain:Efficient,compact,low-cost,low laser-plasma instabilities,beam color selectable from 2ω/3ω/4ω,applicable to multiple laser fusion schemes

The achievement of ignition at the National Ignition Facility(NIF)has prompted a global wave of further research on inertial fusion energy(IFE).However,IFE requires a target gain G of 30-100,and it is hard to achieve fusion at such high gain with the energy,configuration,and technical approach of the NIF.Here,we present a conceptual design for a next-generation laser driver that is applicable to multiple laser fusion schemes and provides 10 MJ,2-3 PW at 3ω(or 2ω,in which case the energy and power can be higher),and one shot per 30 min,with the aim of achieving G>30.It is also efficient,compact,and low in cost,and it has low susceptibility to laser-plasma instabilities.

Shape and diffusion instabilities of two non-spherical gas bubbles under ultrasonic conditions

Ultrasonic cavitation involves dynamic oscillation processes induced by small bubbles in a liquid under the influence of ultrasonic waves. This study focuses on the investigation of shape and diffusion instabilities of two bubbles formed during cavitation. The derived equations for two non-spherical gas bubbles, based on perturbation theory and the Bernoulli equation, enable the analysis of their shape instability. Numerical simulations, utilizing the modified Keller–Miksis equation,are performed to examine the shape and diffusion instabilities. Three types of shape instabilities, namely, Rayleigh–Taylor,Rebound, and parametric instabilities, are observed. The results highlight the influence of initial radius, distance, and perturbation parameter on the shape and diffusion instabilities, as evidenced by the R_0–P_a phase diagram and the variation pattern of the equilibrium curve. This research contributes to the understanding of multiple bubble instability characteristics, which has important theoretical implications for future research in the field. Specifically, it underscores the significance of initial bubble parameters, driving pressure, and relative gas concentration in determining the shape and diffusive equilibrium instabilities of non-spherical bubbles.

Spectral characteristics of laser-plasma instabilities with a broadband laser

Recent experimental progresses regarding broadband laser-plasma instabilities(LPIs)show that a 0.6%laser bandwidth can reduce backscatters of the stimulated Brillouin scattering(SBS)and the stimulated Raman scattering(SRS)at normal incidence[Phys.Rev.Lett.132035102(2024)].In this paper,we present a further discussion of the spectral distributions of the scatters developed by broadband LPIs,in addition to a brief validation of the effectiveness of bandwidth on LPIs mitigation at oblique incidence.SBS backscatter has a small redshift in the broadband case contrary to the blueshift with narrowband laser,which may be explained by the self-cross beam energy transfer between the various frequency components within the bandwidth.SRS backscatter spectrum presents a peak at a longer wavelength in the broadband case compared to the short one in the narrowband case,which is possibly attributed to the mitigation effect of bandwidth on filaments at underdense plasmas.The three-halves harmonic emission(3ω/2)has a one-peak spectral distribution under the broadband condition,which is different from the two-peak distribution under the narrowband condition,and may be related to the spectral mixing of different frequency components within the bandwidth if the main sources of the two are both two-plasmon decays.

Gyrokinetic simulations of the kinetic electron effects on the electrostatic instabilities on the ITER baseline scenario

The linear and nonlinear simulations are carried out using the gyrokinetic code NLT for the electrostatic instabilities in the core region of a deuterium plasma based on the International Thermonuclear Experimental Reactor(ITER)baseline scenario.The kinetic electron effects on the linear frequency and nonlinear transport are studied by adopting the adiabatic electron model and the fully drift-kinetic electron model in the NLT code,respectively.The linear simulations focus on the dependence of linear frequency on the plasma parameters,such as the ion and electron temperature gradientsκ_(Ti,e)≡R=L_(Ti,e),the density gradientκ_(n)≡R/L_(n)and the ion-electron temperature ratioτ=T_(e)=T_(i).Here,is the major radius,and T_(e)and T_(i)denote the electron and ion temperatures,respectively.L_(A)=-(δ_(r)lnA)^(-1)is the gradient scale length,with denoting the density,the ion and electron temperatures,respectively.In the kinetic electron model,the ion temperature gradient(ITG)instability and the trapped electron mode(TEM)dominate in the small and large k_(θ)region,respectively,wherek_(θ)is the poloidal wavenumber.The TEMdominant region becomes wider by increasing(decreasing)κ_(T_(e))(κ_(T_(i)))or by decreasingκ_(n).For the nominal parameters of the ITER baseline scenario,the maximum growth rate of dominant ITG instability in the kinetic electron model is about three times larger than that in the adiabatic electron model.The normalized linear frequency depends on the value ofτ,rather than the value of T_(e)or T_(i),in both the adiabatic and kinetic electron models.The nonlinear simulation results show that the ion heat diffusivity in the kinetic electron model is quite a lot larger than that in the adiabatic electron model,the radial structure is finer and the time oscillation is more rapid.In addition,the magnitude of the fluctuated potential at the saturated stage peaks in the ITGdominated region,and contributions from the TEM(dominating in the higher k_(θ)region)to the nonlinear transport can be neglected.In the adiabatic electron model,the zonal radial electric field is found to be mainly driven by the turbulent energy flux,and the contribution of turbulent poloidal Reynolds stress is quite small due to the toroidal shielding effect.However,in the kinetic electron model,the turbulent energy flux is not strong enough to drive the zonal radial electric field in the nonlinear saturated stage.The kinetic electron effects on the mechanism of the turbulence-driven zonal radial electric field should be further investigated.

Observing eddy dye patches induced by shear instabilities in the surf zone on a plane beach

The effects of surf zone eddy generated by alongshore currents on the deformation and transport of dye are still poorly understood,and related tracer release experiments are lacking.Therefore,a tracer release laboratory experiment was conducted under monochromatic,unidirectional incident waves with a large incident angle(30°)on a plane beach with a 1:100 slope in a large wave basin.A charge-coupled device suspended above the basin recorded the dye patch image.The evolution of eddy dye patch was observed and the transport and diffusion were analyzed based on the collected images.Subsequently,a linear instability numerical model was adopted to calculate the perturbation velocity field at the initial stage.The observation and image processing results show that surf zone eddy patches occurred and were separated from the original dye patches.Our numerical analysis results demonstrate that the structure of the perturbation velocity field is consistent with the experimental observations,and that the ejection of eddy patches shoreward or offshore may be ascribed to the double vortex.

Surgical Treatment of Anterior Shoulder Instabilities Using the Latarjet Technique (about 40 Cases)

Purpose: Surgical treatment of chronic anterior shoulder instability is a difficult therapeutic challenge for contact athletes. The aim of our study is to evaluate the clinical and radiological results of 40 cases of chronic anterior shoulder instability treated in our institution by Latarjet technique. Methods: We report our experience with the intervention of Latarjet modified by the analysis of a retrospective study of 40 cases. They were all young athletic men, with an average age of 29 years with a predominance of the dominant shoulder. Results: Eighty percent had bone lesions, the first dislocation being traumatic (plating). One patient had a recurrence of his instability due to a new trauma and 67% resumed sport within an average period of eight months, some of whom still had functional discomfort in sports practice (9 patients). After an average follow-up of 75 months, 93% of patients were satisfied with their intervention. Only two mechanical complications were observed. Conclusion: Chronic anterior shoulder instability is pathology of young and active subjects. The preregulenoid coracoid block according to Latarjet represents the therapeutic method of choice in the treatment of chronic anterior instabilities of the shoulder, especially in young and athletic subjects. The result of this intervention remains good despite the complications that can occur such as pseudarthrosis, osteoarthritis, lysis or mobility of the screw.

不同类型贴布对慢性踝关节不稳患者行走时踝关节运动学的影响

背景:慢性踝关节不稳患者行走时倾向于过度足内翻,这将增加步行周期支撑相踝关节扭伤的风险。临床医生常使用肌内效贴布或运动贴布进行踝关节贴扎。由于肌内效贴布具有弹性,而运动贴布无法拉伸,因此两者技术应用和生理机制存在差异,进而可能产生不同的康复疗效。目的:对比肌内效贴布和运动贴布干预对慢性踝关节不稳患者步行支撑相足额状面和胫骨水平面运动的影响。方法:40名慢性踝关节不稳患者随机分为肌内效贴布组和运动贴布组,肌内效贴布组从后足内侧向外侧粘贴2条贴布,以产生外翻拉力;运动贴布组采用踝关节闭锁式编篮贴扎。分别于贴扎前后在电动跑台上进行行走测试,利用三维运动分析系统获取受试者足部和胫骨运动学参数。结果与结论:肌内效贴布组贴扎后于支撑相早期足外翻角度增加(P<0.05),但对支撑相晚期足的位置无影响(P>0.05);运动贴布组贴扎后于支撑相晚期胫骨内旋增加(P<0.05),而支撑相早期胫骨位置无明显改变(P>0.05)。结果表明:与运动贴布相比,肌内效贴布能够提供灵活的拉力,有利于步态周期中支撑相早期足外翻,同时不限制支撑相晚期的正常足内翻。因此,肌内效贴布可能是慢性踝关节不稳患者的实用康复疗法,在纠正踝关节异常运动的同时不限制其自然运动。

自旋-轨道耦合作用下极化激元凝聚中的调制不稳定性

利用线性稳定性分析方法,对存在自旋-轨道耦合(SOS)作用的二维极化激元玻色-爱因斯坦凝聚(BEC)系统中的调制不稳定性(MI)进行了研究.分析了组分内部,组分之间以及SOC相互作用对系统调制不稳定性的影响.结果显示,当系统内部不存在SOC作用,组分之间的相互作用为0,组分内部存在排斥作用时,不会出现调制不稳定性,组分内部存在吸引作用时,会出现调制不稳定性,并且调制不稳定性区间长度随吸引作用的增强而增加;组分之间相互作用不为0时,组分之间的相互作用以平方形式出现,其正负不会对调制不稳定性产生实质性影响.存在SOC相互作用时,SOC相互作用会引起增益谱曲线的不规则振荡,破坏原来的调制不稳定性区间.

微卫星不稳定型胃癌免疫治疗的研究进展

微卫星不稳定(microsatellite instability,MSI)型胃癌是一种特殊类型的胃癌,约占总病例数的22%。微卫星是基因组中短串联重复序列的区域,而稳定性指的是这些序列在细胞分裂和DNA复制过程中保持不变。在MSI型胃癌中,这种不稳定性通常是由DNA错配修复基因(如MLH1、MSH2、MSH6等)突变或失活引起的,导致DNA修复能力降低,结果是肿瘤细胞的基因组发生大量的微卫星序列变异和突变。尽管MSI型胃癌的发病率相对较低,但多项研究表明它对免疫治疗显示出良好的治疗效果,同时作为良好预后的预测因子也得到了广泛认可。本文对MSI型胃癌患者基于免疫治疗的综合治疗研究现状进行全面总结和综述,旨在为这类患者的临床治疗提供更多可靠依据。

基于CDoubleGAN的电网时序暂态数据生成

为解决电力系统人工智能应用中样本数量不足的问题,对时序数据生成方法进行研究,提出一种CDoubleGAN模型。结合编解码器和两对生成器-鉴别器,采用ARFNN替代RNN解决Lipschitz连续性问题,实现使用Wasserstein距离对目标函数的稳定优化。将数据类别标签融入模型中,生成特定类别的样本。在IEEE-39系统的实验结果表明,CDoubleGAN在类别生成上的准确度超过98%,与TimeGAN相比,生成的数据与原数据具有更高的相似度,更好保留了数据原始特性以应用于数据生产。

库岸塔柱状危岩的压裂耦合损伤-突变失稳预测

位于三峡库区巫峡段消落带的塔柱状危岩,其底部多损伤因素的耦合作用下常呈压裂诱发座溃整体失稳模式,危岩底部耦合损伤至突变机制是研究该类库岸危岩体失稳预警的关键科学问题.以三峡库区库岸巫峡段箭穿洞塔柱状危岩体为例,将危岩体简化为中上部非劣化区和下部劣化区的二元地质力学模型,基于应变等价原理获得其危岩体下部劣化区的荷载效应、溶蚀效应、干湿循环弱化效应的耦合损伤本构模型和总损伤度演化方程,根据地质力学模型概化为等效弹簧模型转化为力-位移的耦合损伤本构方程;基于能量平衡原理和突变理论建立了塔柱状危岩的耦合损伤-折叠突变模型,获取了其失稳判据和临界位移的表达式.通过案例分析结果表明:该危岩体突变失稳时的系统控制变量为-0.0073,预测模型计算理论的突变起点垂向位移为42.2mm,终止点位移为60.5mm,当监测数据危岩体最大垂向累积位移为26.2mm时,小于突变起始位移时就采用及时治理措施,与危岩未失稳的状态吻合.其研究成果可为三峡库区灰岩地区库岸塔柱状压溃型危岩的监测预警与防治提供重要的理论支撑.

基于MPC的轮毂电机驱动车辆轨迹跟踪控制

为解决轮毂电机驱动车辆在复杂工况下轨迹跟踪精度低、横摆稳定性差的问题,提出一种协调控制方法。通过神经网络动态辨识以车辆质心侧偏角-质心侧偏角速度相平面划分的稳定域边界,并基于边界线特征值得出失稳因子;将该因子作为目标函数权重影响参数,构建轨迹跟踪MPC模型,输出前轮转角和四轮力矩控制量,同时,采用滑模控制方法防止车轮过度滑转。仿真表明,该轨迹跟踪控制策略与单目标MPC轨迹跟踪控制策略相比,在低附着路面车辆最大横向跟踪误差降低了61.7%,最大质心侧偏角降低了75.7%,车辆高速行驶时,运动状态均保持在稳定域范围内,实现了轨迹跟踪精度与车辆横摆稳定性能的综合提升。

功能性踝关节不稳男性下蹲跳过程中下肢的生物力学特征

背景:踝关节作为人体的末端承重关节,承受着机体自上而下的压力,这导致踝关节在运动中很容易发生损伤,诱发功能性踝关节不稳,对日常生活造成负面影响。研究功能性踝关节不稳患者在下蹲跳过程中的下肢生物力学表现,对实现科学训练、预防踝关节损伤以及伤后临床康复提供理论参考具有重要意义。目的:探究功能性踝关节不稳患者下蹲跳过程中的下肢运动学与动力学特征。方法:于2023年3-9月在苏州大学招募男性功能性踝关节不稳患者与健康人群各15名,年龄22-28岁,所有受试者均完成下蹲跳试验。采用Vicon红外高速运动捕捉系统和Kistler三维测力台对两组受试者在下蹲跳起跳阶段、离地瞬间时刻、初始着地时刻和垂直地面反作用力峰值时刻的下肢运动学和动力学指标进行同步采集及对比分析。结果与结论:(1)离地瞬间时刻,与健康对照组的匹配侧相比,功能性踝关节不稳组患侧显示出了更小的膝关节内旋力矩(P=0.020)、更小的踝关节内旋力矩(P=0.009)。(2)落地瞬间时刻,与健康对照组的匹配侧相比,功能性踝关节不稳组患侧显示出了更小的髋关节屈曲角度(P=0.039);功能性踝关节不稳组相较于健康对照组显示出了更小的髋关节外展角度(P=0.022)、更小的膝关节内翻角度(P=0.010)、更大的膝关节外旋角度(P=0.021)、更小的踝关节内翻角度(P=0.004)、更小的踝关节外旋角度(P=0.008)。(3)垂直地面反作用力峰值时刻,功能性踝关节不稳组相较于健康对照组显示出了更小的踝关节内翻角度(P=0.044);(4)结果说明,功能性踝关节不稳者在下蹲跳动作中相较于健康人群存在异常的下肢生物力学特征,主要表现为离地与落地瞬间时刻,下肢关节在矢状面和额状面的运动学和动力学指标变化。这些改变反映出功能性踝关节不稳人群在执行下蹲跳时采用了僵硬的起跳与着陆模式,倾向于将患侧踝关节负荷转移至下肢其他关节,并显示出健侧下肢的代偿现象。因此,检测和纠正异常生物力学特征应该成为功能性踝关节不稳者康复训练的一部分。

Navigating medial patellotibial ligament reconstruction:Clinical perspectives and surgical strategies

The surgical approach for patellar instability usually refers to reconstruction of the medial patellofemoral ligament associated with an osteotomy of the tibial tuberosity or a trochleoplasty when required.The medial patellotibial ligament and the medial patellomeniscal ligament are secondary stabilizers of the patella.Despite this,both the medial patellotibial and patellofemoral ligaments aid in patellar rotation and tilt when the knee is flexed beyond 45°.The medial patellotibial ligament plays a particularly important role in the final stages of stretching in extension and between 40 degrees to 90 degrees of flexion.The clinical relevance and surgical indications for medial patellotibial ligament reconstruction associated with medial patellofemoral ligament reconstruction are still controversial.This editorial explores the surgical indications and clinical results for medial patellotibial ligament reconstruction to improve readers’understanding of this technique,especially because reported clinical outcomes have remained sparse.

霍尔推力器中电子碰撞及等离子体密度和磁场梯度激发的不稳定性

在霍尔推力器中,电子漂移、电子碰撞,以及等离子体密度、温度、磁场梯度所蕴含的自由能会驱动各种频率和波长的不稳定性.不稳定性的存在会破坏等离子体的稳定放电,削弱推力器与电源处理单元的匹配度,降低推力器的性能.基于此,本文利用基于流体模型推导的色散关系研究了霍尔推力器中由电子碰撞、等离子体密度和磁场梯度驱动的不稳定性.结果表明:1)在考虑电子惯性、电子与中性原子的碰撞,以及电子E×B漂移时能够在推力器近阳极区到羽流区内的任一轴向位置处激发不稳定性.随着角向波数ky的增大(k=2π/λ,λ为波长),模式将从由碰撞激发的低杂波不稳定性转变为离子声波不稳定性.当ky=10 m−1时,最大增长率γ_(max)对应频率ωr随着碰撞频率νen的增大而轻微减小;当ky=300 m−1时,γ_(max)对应的频率ωr以及最大频率ω_(rmax)几乎不随碰撞频率变化.不依赖于ky的大小,对于碰撞激发的不稳定性,模式的增长率随着碰撞频率的增大而增大.2)同时考虑电子惯性、电子碰撞效应,以及密度梯度时,密度梯度对驱动不稳定性占主导作用.模式的动力学行为不会随ky的增大而变化,但模式的本征值随ky的增大而增大.在密度梯度κN=0的两侧,由于密度梯度引起的抗磁性漂移频率ωs的符号发生了变化,模式的本征值在κN=0两侧有相反的变化趋势:当ω∗与ωr符号相反时,密度梯度对不稳定性的激发有削弱作用(κN>0);当ω∗与ωr符号相同时,密度梯度对不稳定性的激发有增强作用(κN<0).3)在模型中同时考虑等离子体密度梯度、磁场梯度,以及电子惯性和碰撞效应时,模式本征值的变化依赖于电子的漂移频率,以及密度和磁场梯度引起的抗磁性漂移频率的相对大小.当仅包含密度梯度和磁场梯度时,推力器放电通道内将出现稳定窗,即增长率为0的区间;包含电子惯性和碰撞效应后,稳定窗消失.

弱旋预混火焰中热声振荡多模态转换的实验与模拟研究

为研究弱旋预混火焰在当量比变化过程中热声不稳定的频率迁移、模态转换特征及内在机理,通过傅里叶变换、相空间重构、OH*时序及平均火焰图像等方法对实验中出现的极限环、拍振、间歇性振荡等典型燃烧不稳定状态进行分析;结合低阶热声网络与n-τ模型,对热声振荡过程中发生的模态转换现象进行模拟,其中延迟时间τ使用了对流延迟时间进行近似,其基于未燃混合物长度计算得到。实验结果表明,在当量比φ=0.5~0.7内,随着当量比的增加,一阶振荡频率向更高频率迁移;在φ=0.8时,振荡主频从一阶模态转换到二阶模态;φ=0.9~1.2内,一阶振荡频率降低,变化幅度最高达41.48%;并且当φ=1.1时,振荡主频从二阶模态转换回一阶模态;在整个当量比区间内,二阶振荡频率变化幅度小于5%。计算结果显示,振荡频率的预测值与实验值整体吻合良好,尤其是当φ=0.8时,二阶频率的增长率大于一阶频率的增长率,对应实验中发生的一阶模态到二阶模态的转换。同时在部分工况下,预测的振荡频率与实验值也有偏移,其原因是增益的增加导致偏离增大,一阶频率的最大误差为26.4%,二阶频率的最大误差小于12%。本研究表明,对流延迟时间与振荡主频的分布存在反比关系,对流延迟时间的缩短会使得一阶频率向高频迁移,过程中振荡模态会由一阶转换到二阶模态。

基于小尺寸模型分析氢氧旋转爆轰波传播的不稳定性机制

氢氧的高反应活性给旋转爆轰波的稳定传播带来了巨大的挑战,为研究氢氧旋转爆轰波传播不稳定性,通过改变当量比对小尺寸模型下二维氢氧旋转爆轰波进行数值模拟研究,揭示了氢氧旋转爆轰波复杂多变的传播特性,并分析了典型流场结构,探讨了传播模态的不稳定性以及爆轰波湮灭和再起爆机制。结果表明:随着当量比的提高,流场内分别呈现熄爆、单波、单双波混合3种传播模态,且爆轰波的传播速度随当量比的增大几乎呈线性提高,速度亏损为5%~8%。激波的扰动使得爆燃面失稳产生明显的扭曲和褶皱,氢氧的高反应活性让爆燃面明显分层且在2个分界面上呈现不同的不稳定性,上分界面为Kelvin-Helmholtz(K-H)不稳定性,下分界面为Rayleigh-Taylor(R-T)不稳定性。单双波混合模态下爆轰波极不稳定,保持湮灭、单波、双波对撞3种状态之间循环。爆轰波有2种湮灭方式:一是双波对撞导致爆轰波湮灭,二是爆燃面燃烧加剧使得爆燃面下移导致爆轰波湮灭。再起爆的主要原因是:R-T不稳定性诱导爆轰产物与新鲜预混气在爆燃面上相互挤压产生尖峰和气泡结构,增强爆燃面上的反应放热,产生了局部热点并逐渐增强为爆轰波,实现爆燃转爆轰。

基于机器学习构建中青年人群颈椎失稳临床预测模型

背景:颈椎失稳是中青年人群常见骨科疾病,是颈椎病早期表现,对患者生活质量影响较大。因此,早期诊断颈椎失稳以实施早期干预具有积极的临床意义和社会意义。目的:基于机器学习构建中青年人群颈椎失稳临床预测模型,在进行X射线片检查之前,实现中青年人群颈椎失稳早期筛查。方法:2022年9月至2023年10月通过招募广告和中国中医科学院望京医院脊柱科门诊招募155例中青年颈椎失稳受试者和88例非颈椎失稳受试者作为研究对象,基于调查问卷形式现场采集受试者一般信息、生活工作习惯、不适症状、颈痛目测类比评分、颈椎功能障碍指数、健康调查简表(SF-36)等信息,并将以上信息作为预测因子,经筛选后,以支持向量机、轻量的梯度提升机、随机森林、逻辑回归分析、自适应提升算法、极致梯度提升分类器6种机器学习算法采用十折交叉验证方法进行模型训练,构建颈椎失稳临床预测模型,以曲线下面积为主要评价指标。将预测因子进行单因素分析,并采用SHAP方法对预测因子的重要性进行排序,以相关性热力图展现预测因子之间及其与颈椎失稳之间的线性相关程度。结果与结论:①6种机器学习模型中,选用随机森林模型为最终预测模型,包含年龄、体质量指数、颈围/颈长、颈痛目测类比评分、颈椎功能障碍指数、SF-36健康状况量表躯体疼痛、总体健康、生命活力、精神健康评分9个预测因子,曲线下面积=0.7254,具有良好的预测能力,可作为早期筛查中青年人群颈椎失稳的参考工具;②两组受试者的年龄、颈痛目测类比评分、颈椎功能障碍指数、SF-36健康状况量表躯体疼痛、总体健康、生命活力评分相比差异有显著性意义(P<0.05);③预测因子重要性排序为年龄、颈椎功能障碍指数、颈痛目测类比评分、总体健康、体质量指数、生命活力、躯体疼痛、颈围/颈长、精神健康,其中年龄、颈痛目测类比评分、颈椎功能障碍指数与颈椎失稳呈正相关,总体健康、体质量指数、生命活力、躯体疼痛、颈围/颈长、精神健康与颈椎失稳呈负相关。

晚更新世以来长江流域河流阶地年龄数据库及其对成因分析的指示意义

研究长江流域河流阶地的形成规律,对深入理解河流阶地的主要驱动因素,预测长江流域演化趋势以及保障沿岸人民生存发展具有重要意义。系统收集并整理了长江流域河流阶地的660条年代学数据,建立了河流阶地年龄数据库及其年龄概率密度函数,并探讨了长江流域河流阶地的形成机制。结果表明:近200 ka以来,长江流域中游和上游地区河流阶地概率密度曲线在约11 ka、约23 ka、约40 ka、约44.8 ka、约56.25 ka等多个时期出现了明显的峰值,这些峰值与全球气候变暖、黄土高原古降水量和洞穴氧同位素值的剧烈波动时期高度吻合,长江流域上游地区的河流阶地在山地地区的发育频率较高;长江流域中游和上游地区河流阶地年龄概率密度曲线的峰值主要出现在全球气候突变期,且河流阶地在构造抬升强烈的时期及地区发育更广泛;长江流域河流阶地是在构造运动和气候变化共同作用下形成的,其中气候的剧烈变化作为触发因子通过破坏河道稳定性,促使河流下切并形成阶地,而区域构造抬升运动则为河流提供了下切的空间,使得河流阶地对气候变化的响应更加敏感,从而推动了河流阶地的形成,尤其在气候相对变暖的时期,河流阶地的形成频率明显更高。

Wind Turbine Composite Blades:A Critical Review of Aeroelastic Modeling and Vibration Control

With the gradual increase in the size and flexibility of composite blades in large wind turbines,problems related toaeroelastic instability and blade vibration are becoming increasingly more important.Given their impact on thelifespan of wind turbines,these subjects have become important topics in turbine blade design.In this article,firstaspects related to the aeroelastic(structural and aerodynamic)modeling of large wind turbine blades are summarized.Then,two main methods for blade vibration control are outlined(passive control and active control),including the case of composite blades.Some improvement schemes are proposed accordingly,with a specialfocus on the industry’s outstanding suppression scheme for stall-induced nonlinear flutter and a new high-frequencymicro-vibration control scheme.Finally,future research directions are indicated based on existingresearch.