Gyro-Landau-fluid simulations of impurity effects on ion temperature gradient driven turbulence transport

The effects of impurities on ion temperature gradient(ITG)driven turbulence transport in tokamak core plasmas are investigated numerically via global simulations of microturbulence with carbon impurities and adiabatic electrons.The simulations use an extended fluid code(ExFC)based on a four-field gyro-Landau-fluid(GLF)model.The multispecies form of the normalized GLF equations is presented,which guarantees the self-consistent evolution of both bulk ions and impurities.With parametric profiles of the cyclone base case,well-benchmarked ExFC is employed to perform simulations focusing on different impurity density profiles.For a fixed temperature profile,it is found that the turbulent heat diffusivity of bulk ions in a quasi-steady state is usually lower than that without impurities,which is contrary to the linear and quasilinear predictions.The evolutions of the temperature gradient and heat diffusivity exhibit a fast relaxation process,indicating that the destabilization of the outwardly peaked impurity profile is a transient state response.Furthermore,the impurity effects from different profiles can obviously influence the nonlinear critical temperature gradient,which is likely to be dominated by linear effects.These results suggest that the improvement in plasma confinement could be attributed to the impurities,most likely through adjusting both heat diffusivity and the critical temperature gradient.

Gradient Differentiation and Exploitation Mode of Tourist Resources in Hailuogou Scenic Area,China

Natural environment of Hailuogou Scenic Area(Conch Gully)was introduced,and it was pointed out that tourist resources in the study area showed gradient differentiation along the vertical height.In view of such gradient differentiation,resource contents and characteristics of its cultural heritages zone,geothermal resources zone,forest vegetation zone,and glacial resources zone were respectively analyzed.Based on the gradient differentiation of tourist resources in Hailuogou Scenic Area,suggestions were given for its further tourism development,and it was stressed that brand effects of the attractions should be enhanced,infrastructure construction and maintenance of newly-explored scenic spots should be improved,and more efforts should be devoted to explore disastrous landform resources.This research is of practical significance for studying spatial differentiation and evolution mechanism of tourist resources in mountainous areas in western China,and also provides scientific support for the exploration of tourist resources in mountainous areas.

Assignment of terahertz vibrational modes of L-glutamine using density functional theory within generalized-gradient approximation

The crystal structure of L-glutamine is stabilized by a three-dimensional network of intermolecular hydrogen bonds.We utilize plane-wave density functional theory lattice-dynamics calculations within the generalized-gradient approximation（GGA）, Perdew–Burke–Ernzerhof（PBE）, PBE for solids（PBEsol）, PBE with Wu–Cohen exchange（WC）, and dispersion-corrected PBE, to investigate the effect of these intermolecular contacts on the absorption spectra of glutamine in the terahertz frequency range. Among these calculations, the solid-state simulated results obtained using the WC method exhibit a good agreement with the measured absorption spectra, and the absorption features are assigned with the help of WC. This indicates that the vibrational modes of glutamine were related to the combination of intramolecular and intermolecular motions, the intramolecular modes were dominated by rocking or torsion involving functional groups; the intermolecular modes mainly result from the translational motions of individual molecules, and the rocking of the hydrogenbonded functional groups.

Gradient structure induced simultaneous enhancement of strength and ductility in AZ31 Mg alloy with twin-twin interactions

Gradient nanostructure was introduced to enhance the strength and ductility via deformation incompatibility accommodated by geometrical necessary dislocations for most metallic materials recently.However,few intensive researches were carried out to investigate the effect of gradient structure on the deformation twin evolution and resulting performance improvements.In the present paper,we produced gradient-structured AZ31 Mg alloy with fine-grain layers,parallel twin laminates and a coarse-grain core from two upmost surfaces to the center of plate.Surprisingly,this architected Mg alloy exhibited simultaneous enhancement of strength and ductility.Subsequent microstructural observations demonstrated that abundant twin-twin interactions resulting from higher strength and multi-axial stress state could make great contributions to the increase of work-hardening capability.This was further proved by the measurement of full-field strain evolution during the plastic deformation.Such a design strategy may provide a new path for producing advanced structure materials in which the deformation twinning works as one of the dominant plasticity mechanisms.

Improvement of photoemission performance of a gradient-doping transmission-mode GaAs photocathode

Two types of transmission-mode GaAs photocathodes grown by molecular beam epitaxy are compared in terms of activation process and spectral response, one has a gradient-doping structure and the other has a uniform-doping structure. The experimental results show that the gradient-doping photocathode can obtain a higher photoemission capability than the uniform-doping one. As a result of the downward graded band-bending structure, the cathode performance parameters, such as the electron average diffusion length and the surface electron escape probability obtained by fitting quantum yield curves, are greater for the gradient-doping photocathode. The electron diffusion length is within a range of from 2.0 to 5.4μm for doping concentration varying from 10^19 to 10^18 cm^-3 and the electron average diffusion length of the gradient-doping photocathode achieves 3.2 μm.

Effects of Finite Aspect Ratio and Noncircular Plasma Flux Surface on Electron Temperature Gradient Driven Modes

A gyrokinetic model with integral eigenmode equations is developed based on the local equilibrium of shaped tokamak plasmas. Effects of main geometric parameters （finite aspect ratio, elongation, triangularity, and Shafranov shift gradient） on the electrostatic electron temper- ature gradient （ETG） driven modes are investigated numerically. It is found that the finite aspect ratio has a general stabilizing effect, while the elongation can be either stabilizing or destabilizing, depending on the poloidal wavelength of the mode and other parameters. It is shown that a low aspect ratio enhances the stabilizing effect of elongation, and weakens its destabilizing effect as well.

Derivation of General Formula for Coupling Loss of Single-mode Fiber Collimators with Gradient-index Rod Lenses

Gradient-index rod lens (GRIN-lens) whose pitch is ordinary value with bevel ferrule coupling system is analyzed, an equivalent method which can be used to analyze this system is put forward, and a general formula for determining the coupling loss with axes mismatch, radial mismatch, and angular mismatch is derived by use of the Gaussian field approximation and mode-field coupling theory. The experimental results are in good agreement with the theory prediction. It indicates that these formulas are suitable to analyze the gradient-index rod lens coupling system with pigtail fiber.

Water Gauge Image Denoising Model Based on Improved Adaptive Total Variation

As an important part of water level warning in water conservancy projects,often due to the influence of environmental factors such as light and stains,the acquired water gauge images have sticky,broken and bright spot conditions,which affect the identification of water gauges.To solve this problem,a water gauge image denoising model based on improved adaptive total variation is proposed.Firstly,the regular term exponent in the adaptive total variational equation is changed to an inverse cosine function;secondly,the differential curvature is used to distinguish the image noise points and increase the smoothing strength at the noise points;finally,according to the characteristics of the gradient mode and adaptive gradient threshold after Gaussian filtering,the New model can adaptively denoise in the smooth area and protect the edge area,so as to have the characteristics of both edge-preserving denoising.The experimental results show that the new model has a great improvement in image vision,higher iteration efficiency and an average increase of 1.6 dB in peak signal-to-noise ratio,and an average increase of 9%in structural similarity,which is more beneficial to practical applications.

共模抑制的渐变结构高速差分电路设计

本文构建了一种拐角分段阻抗控制的渐变结构高速电路差分线,采用了HFSS三维电磁仿真软件对差分信号进行了建模分析。对混模S参数的仿真分析结果表明:对比平行结构的差分信号设计方式,所提出的添加GND孔渐变结构差分信号在10 GHz范围内差模转差模增大了58.7%,差模转共模减小了38.3%。通过对实物测试显示:添加GND孔渐变结构差分线的S_(d2d1)参数和S_(c2d1)仿真结果和实测结果具有很好的一致性,差分电路差模转共模得到了有效地抑制,对应的差分信号传输效率得到了提升。电场分布表明:渐变结构设计方法极大改善了差分电路转角位置电场分布,避免了差分电路传输线间电场聚集,使差分信号共模噪声和反射损耗减小,实现了高速差分信号传输的连续性。

基于等效阻抗渐变变压器的宽带压控振荡器

设计了一种基于65 nm CMOS工艺的毫米波宽带压控振荡器(VCO)。分析了应用于宽带VCO的宽带化技术。针对高频相位噪声性能恶化这一问题,提出并设计了一种等效阻抗渐变变压器,以优化VCO高频段相位噪声。该压控振荡器输出信号频率为20.4~40.2 GHz,覆盖24~26 GHz、38~39 GHz两个5G毫米波通信频段。全频带内,相位噪声小于-102 dBc/Hz,品质因子大于180.9 dBc/Hz。

基于WOA-VMD-XGBoost的混凝土坝变形预测

建立混凝土坝高精准变形预测模型是掌握坝体结构服役性态的关键,而其变形监测数据具有复杂的非线性和非平稳特征,会影响预测模型的精度及泛化能力。针对上述问题,引入鲸鱼优化算法(WOA)和包络熵理论自适应寻优变分模态分解(VMD)参数,根据最佳参数组合多尺度分解变形数据,得到多个不同特征尺度的本征模态函数(IMF)。通过重构分量为新分量,将新分量分别输入极端梯度提升(XGBoost)模型中进行预测,叠加各预测结果得到最终预测值。基于山口岩碾压混凝土拱坝变形监测数据,开展支持向量回归机(SVR)、随机森林(RF)、XGBoost、WOA-VMD-XGBoost等4种模型的精度、泛化能力对比研究。结果表明:相比于单一预测模型,组合模型有效挖掘了变形信号多尺度特征,降低了非线性、非平稳性对模型性能的影响,在精度、泛化能力中表现出更高性能。该组合模型为大坝变形监测提供了理论依据和应用参考。

基于煤矸石中锂、镓元素赋存状态的高梯度磁选预富集试验

我国山西、内蒙古部分矿区煤矸石中蕴藏着锂、镓等战略性关键金属,其锂、镓元素富集逐渐成为研究热点。然而煤矸石中锂、镓含量很低,直接浸出需消耗大量化学药剂,高效、经济的富集锂、镓元素仍存在很大挑战。为提高煤矸石中锂、镓富集效率,针对山西朔州地区煤矸石中锂、镓元素赋存状态和预富集方法展开研究。采用逐级化学提取法、矿物物相组成、矿物解离分析、电感耦合等离子体质谱法、扫描电子显微镜和能量色散光谱,研究了煤矸石中锂、镓元素的赋存状态,利用高梯度磁选探究通过抛除黄铁矿对煤矸石中锂、镓元素预富集的可行性。结果表明,煤矸石主要由高岭土、黄铁矿、石英、方解石、白云母等矿物组成,锂、镓元素主要赋存于硅酸盐类矿物中,黄铁矿中含量较少。原矿中锂质量分数146.37μg/g,镓质量分数25.04μg/g。通过磁选方法抛除黄铁矿可对煤矸石中锂、镓元素预富集,1000 mT时,预富集效果最佳,磁选尾矿中锂质量分数210.63μg/g,为原矿中锂含量的1.45倍,锂回收率88.00%。镓质量分数31.88μg/g,高于原矿中镓元素,镓回收率80.07%。

专精特新企业成长与培育的研究回顾与未来研究展望

专精特新企业高质量成长与培育正成为新兴热点研究主题。已有研究对其概念、成长因素、培育路径等内容进行了初步探讨,但仍然缺乏系统梳理和深入分析。基于此,本研究聚焦于专精特新企业的成长与培育这一研究主题进行梳理分析。首先,界定了专精特新企业的概念,阐释了梯次分类法和波特竞争战略分类法两种视角下的专精特新企业分类;其次,基于“动因-过程-结果”的逻辑主线,构建专精特新企业成长与培育的理论框架,通过与德国隐形冠军企业进行对比分析,揭示了我国专精特新企业成长与培育的动因;梳理出专精特新企业成长与培育过程中的五个关键因素,解释了专精特新企业成长与培育的过程;总结出四种培育模式和与此相匹配的四种梯度培育路径,呈现了专精特新企业成长与培育的结果。最后,构建了专精特新企业成长与培育整合的理论框架,提出专精特新企业成长与培育的管理启示和未来展望,为专精特新企业高质量发展提供理论参考和实践依据。

基于VMD与优化LightGBM的混凝土拱坝变形预测

变形是反映混凝土拱坝安全运行状态的重要指标,因此变形预测模型的研究对拱坝结构健康评价具有重要意义。为充分挖掘拱坝变形监测数据的有效信息,提高监控模型的预测精度,提出一种基于变分模态分解与优化LightGBM的混凝土拱坝变形预测模型。首先,采用VMD将变形实测数据分解为多个模态分量;其次,引入改进灰狼算法与LightGBM相结合建立混凝土拱坝变形预测模型;随后,对模态分量进行单独建模和预测,最后叠加以得到最终的预测结果。工程实例分析表明,通过有效地分解重构,构建的变形预测模型具有较高的预测精度和泛化性能。

基于变增益最速梯度下降法的表贴式永磁同步电机位置修正策略

滑模观测器具有响应速度快、鲁棒性强等优点,已广泛应用于表贴式永磁同步电机无位置传感器的中、高速控制系统。然而,具有固定参数的滑模观测器很难在宽速度范围内保持一致的估算精度,而采用基于速度观测器带宽限制的方法进行噪声和扰动抑制会降低电机的动态性能。针对上述问题,该文首先分析滑模观测器估算表贴式永磁同步电机转子位置的误差产生机理,提出一种新型位置误差观测器,主要思想是基于磁链观测进行位置误差连续估算,并采用最速梯度下降法对积分过程进行反馈校正;然后,通过变增益循环迭代优化提高位置误差观测器的速度与准确性;最后搭建表贴式永磁同步电机加载测试平台进行实验,结果验证了所提方法具有位置观测精度高、鲁棒性强的特点。

梯度模式对Miura-ori超材料力学性能影响的研究

Miura-ori超材料是一种重量轻且多孔的材料,其机械性能通常是由自身的折叠方式和几何形状决定的,它的机械响应可以通过几何设计来进行修正调整,是一种具有多功能的、可调控且设计空间多样的超材料。为研究厚度渐变(Thickness Gradient,TG)模式以及锐角渐变模式对超材料能量吸收能力的影响,结合有限元分析软件参数化分析超材料的力学特性。研究结果表明,TG梯度为负梯度的超材料能量吸收能力较好,并且负梯度时的TG梯度超材料的平均力和能量吸收比锐角梯度超材料表现更佳。

新型梯度连续可控夹层板抗冲击性能研究及优化

研究了一种基于空间填充设计方法与二维泰森多边形方法的梯度连续可控夹层结构的设计方法.通过控制形核点的分布函数,实现夹层结构面内相对密度的径向梯度分布且环向均匀分布,进而对结构的抗冲击性能进行调控设计.利用6061O铝合金加工制备了不同面板厚度的梯度夹层板进行落锤冲击实验,并采用Abaqus/Explicit软件建立了三维有限元分析模型,实验结果和数值模拟结果有较好的一致性.通过实验观测与数值模拟得到梯度夹层板在低速局部冲击载荷作用下的变形机制,基于理想刚塑性金属材料本构建立了低速局部冲击载荷作用下面内梯度夹层板动态响应的理论分析模型,分析了面板与芯层的变形模式与吸能机理.对形核点分布函数特征参数进行了分析,得到了形核点分布函数对梯度夹层板抗冲击性能的影响规律,阐明了特征参数对力学性能的调控机制.以特征参数为设计变量,以低速局部冲击载荷作用下梯度夹层板的抗冲击性能为优化目标,建立多目标优化问题,利用试验设计方法、代理模型技术及多目标遗传算法求解得到Pareto解集,并利用最小距离选择法得到了综合最优解.验证了梯度连续可控夹层结构的设计方法是可行且有效的.

CFQS中离子温度梯度模的同位素效应研究

基于中国首台准环对称仿星器(CFQS),利用回旋动理学弗拉索夫代码GKV率先开展准环对称仿星器中离子温度梯度模(ITG)的同位素效应研究。模拟结果表明,CFQS中存在明显的ITG同位素效应,随着氢同位素质量的增加,ITG的增长率显著下降。通过扫描等离子参数,如不同氢同位素混合的比例、密度梯度以及离子与电子温度比,研究了这些等离子体参数下CFQS中同位素效应的变化。此外,在不同的环向或径向位置处研究了CFQS的三维磁场位形对ITG同位素的影响,发现ITG的同位素效应在不同的环向和径向位置均普遍存在。

基于WOA-VMD-GBDT的长期电力负荷预测

为提高电力负荷的预测精度提出了一种基于鲸鱼优化算法(WOA)改进的变分模态分解(VMD)与梯度提升树(GBDT)结合的长期电力负荷预测方法。首先,利用VMD将长期负荷分解为简单的子序列,并引入WOA解决VMD分解时需人为调参的问题;影响长期负荷预测的经济因素和气象因素同样进行分解并降维,以获得有用特征,降低噪声影响;最后,将IMF分量及特征分量带入GBDT模型,得到多个IMF分量预测值,叠加重构后得到最终的电力负荷预测值。对中国某地区实际电力负荷及经济数据与气象数据分析,实验结果表明,本文模型相比于单一模型其预测精度更高,RMSE、MAE、MAPE三个方面误差更小,R 2也提升到了0.979。

数值求解耦合Gross-Pitaevskii方程组基态解的离散归一化梯度流方法

本文提出了一种求解磁场项为常数的耦合Gross-Pitaevskii方程组基态解的数值方法.基于单组分近似理论,本文将方程组的能量函数等价为单组分的能量泛函,然后基于降阶后的能量表达式提出了离散归一化梯度流数值方法.数值算例表明,该方法高效且可靠.