基于奇异摄动分解的弹性飞机乘坐品质控制

考虑弹性飞机在风干扰作用下乘客乘坐舒适性降低,提出一种基于奇异摄动分解的乘坐品质控制方法。针对弹性客机动力学模型,采用奇异摄动理论将模型解耦为刚性慢变子系统和弹性快变子系统。考虑刚性子系统的附加时变扰动和气动不确定影响,设计干扰观测器估计扰动项并采用神经网络处理模型不确定性,将复合估计信息作为前馈补偿并结合俯仰角速率和法向过载跟踪误差反馈给出自适应鲁棒控制策略。针对弹性子系统设计非奇异终端滑模控制,实现振动主动抑制。综合刚弹子系统控制器设计形成弹性客机乘坐品质控制律,实现附加法向过载和弹性模态的快速抑制收敛。基于李雅普诺夫稳定性分析证明了系统的一致终值有界。仿真结果表明,在离散突风和大气紊流作用下所提出的控制方法能够降低客机关键位置处的附加法向过载,有效提升弹性客机乘坐品质。

进动分解及其在转子动平衡中的应用

当转子各向刚性存在明显差异时,传统的基于单向传感器测量的转子平衡方法其效果受方向影响,平衡效果不稳定。提出一种针对影响系数法的改进方法,该方法采用基于双传感器的信息融合方法,将不平衡响应椭圆分解为正进动和反进动圆,并以正进动圆的幅值和初相位作为不平衡响应,取代传统的单传感器测得的响应进行转子平衡,取得了良好的效果。数值模拟的结果表明:在忽略非线性因素情况下,改进方法与传统方法数值趋于一致,且高度兼容;实验验证结果表明:改进方法计算结果客观唯一,精度更高。

中国经济波动分解及异质性货币政策冲击的动态响应机制

文章通过构建随机扰动变参数因子扩展的向量自回归模型(SV-TVP-FAVAR模型),对中国经济波动进行结构性及周期性因素分解,在此基础上给出异质性货币供给冲击对经济变量的动态影响特征。得出以下结论:结构性因素解释经济波动的34.12%,周期性因素解释经济波动的65.88%,两种因素的影响效果明显不同;样本期内,货币政策变量具有3个转折点,分别为1961年、1978年及1996年;不同经济波动成分对货币政策冲击的响应存在较大差异;不同的经济状态也会对货币政策的调控存在影响。

自适应动模式分解和GA-SVM在行星轴承故障分类中的应用

行星齿轮箱在运行过程中由于齿轮间的相互作用会产生强噪声,导致行星轴承的故障特征被完全淹没在背景噪声中并难以提取,从而使得行星轴承故障分类的准确率较低.本文提出一种自适应动模式分解(ADMD)和遗传算法优化支持向量机(GA-SVM)的行星轴承故障分类方法.首先,针对传统动模式分解(DMD)中截断秩无法准确选取的问题,定义了一种新的适应度函数,并采用改进的蚱蜢优化算法(IGOA)自适应选取最优截断秩,进而实现对原始振动信号的降噪处理.然后对处理后的信号计算其归一化后的复合精细多尺度离散熵(IRCMDE)并构成特征矩阵.最后采用遗传算法优化支持向量机,构建GA-SVM分类模型,并将其应用到行星轴承故障诊断中.利用行星齿轮箱中行星轴承故障数据验证了此方法的有效性和实用性,最终分类结果为96.43%,表明了该方法可以准确识别出行星轴承的故障类型.

多维数据表的动素分解、合成和向前推测

多维数据表动态规律的研究焦点,集中在如何克服其数据规模庞大的困难,并同时保护数据系统的整体性质。对此,本文提出了多维数据表动素分解与合成理论,在对动素间的协调性、动素合成方式以及动素分解完备性进行论述和理论证明的基础上,给出了多维动态数据表向前推测的工作步骤。该方法将通过动态分析和推测数据系统主要特征的变化规律,来实现对多维数据表的整体预测,这将使多维数据表推测过程更为简捷、直观和有效。

沥青面层整体动稳定度控制标准的层位分解方法

建立了将沥青面层整体动稳定度分解成各层材料动稳定度的方程,通过对大量沥青混合料和相应沥青面层整体开展的轮辙试验回归得到了方程的相关系数;利用这个分解方程,将设定的沥青面层整体动稳定度控制标准分解到沥青面层各层,得到了层位动稳定度控制标准和厚度的多个组合方案。分析结果表明,这个分解方程可以有效地统一沥青面层结构抗车辙性能和层位抗车辙性能;能够得到各层位动稳定度控制标准的多个组合方案,便于实现结构优选;所得到的各层位动稳定度控制标准综合考虑了沥青混合料所处层位和层厚,弥补了目前规范的不足。

地浸采铀工艺中电潜泵内流场数值模拟研究

电潜泵是我国地浸采铀工艺中实现浸出液有效提升的主要装备,但目前针对介质举升状态下电潜泵水力部件内部流场作用机制的研究较少。试验以叶轮-导叶内部结构为研究对象,应用CFD方法对介质流动特性开展非定常分析,研究了叶轮和叶轮出口段内部的压力脉动变化规律,并利用瞬态流场数据对叶轮截面压力流场进行动模态分解(DMD)与压力流场重构,揭示了介质举升状态下由动静干涉引起的压力脉动周期性变化规律与动静部件距离对动静干涉强度的影响规律。结果表明,叶片通过频率值与快速傅里叶变换(FFT)频率值基本一致。试验结果可对减少由压力脉动引发的泵体无效震动、优化电潜泵水力部件结构参数和提升系统效率提供一定理论参考。

水轮机尾水管涡带压力脉动同步及非同步特性研究

尾水管涡带是混流式水轮机在部分负荷工况运行时尾水管内出现的一种螺旋状涡旋运动,其诱发的压力脉动对水轮机运行稳定性有直接影响且易造成疲劳破坏。基于SSTkω湍流模型对运行在42.35%额定功率的某混流式模型水轮机进行了尾水管内部流动特性的试验测试与数值研究,数值压力脉动幅值及主频与试验测试吻合度好,误差分别约为2.70%和2.62%。尾水管内出现进动涡带时,测点压力均作0.25倍转频的周期性脉动,涡带扫过测点时,其压力最低。位于涡带运动轨迹附近的压力测点,其压力幅值最高。为了进一步阐明尾水管涡带的复杂流动特征及其动力学特性,将尾水管压力信号分解为同步分量及非同步分量。研究发现,分解后的非同步分量对原始信号有较强的依从性,其幅值较高且保持主频为0.25倍转频,而同步分量主频发生变化且压力脉动幅值较小,表明非同步分量对尾水管涡带的形成贡献大于同步分量。尾水管锥管段不同高程上同步及非同步分量幅值的量化分析表明,非同步分量幅值绝对占优,沿流动方向非同步分量幅值先增大后减小,而同步分量幅值逐渐增加。

一种数据驱动的翼型流动转捩预测方法

研究翼型绕流的转捩预测方法,对于翼型流动细节的精确模拟和气动力的准确计算以及精细化设计均具有十分重要的意义.采用动模态分解(dynamic mode decomposition,DMD)代替线性稳定性理论(linear stability theory,LST)与e^N方法结合,不需要求解稳定性方程,成为一种数据驱动的翼型边界层转捩预测新方法,称为DMD/e^N方法.在原有方法的基础上,改进了DMD网格线生成方法和扰动放大N因子的积分策略,并将RANS求解器与改进的DMD/e^N方法进行耦合,实现了翼型定常绕流转捩预测自动化.采用该方法对LSC72613跨声速自然层流翼型以及NLF0416低速自然层流翼型在不同攻角下的绕流进行转捩预测,转捩点计算结果均与实验值和LST/e^N方法吻合良好.该方法计算得到的N值增长曲线与LST/e^N方法的包络线也较为吻合,进一步验证了积分策略的正确性.改进的DMD/e^N方法可作为自然层流翼型设计的新的有力工具.

Characterization of the dissociation pathways of dichloromethane and glutathione in dichloromethane dehalogenase

Dichloromethane(DCM)dehalogenase stands as a crucial enzyme implicated in the degradation of methylene chloride across diverse environmental and biological contexts.However,the unbinding pathways of ligands from DCM dehalogenase remain unexplored.In order to gain a deeper understanding of the binding sites and dissociation pathways of dichloromethane(DCM)and glutathione(GSH)from the DCM dehalogenase,random accelerated molecular dynamics(RAMD)simulations were performed,in which DCM and GSH were forced to leave the active site.The protein structure was predicted using Alphafold2,and the conformations of GSH and DCM in the binding pocket were predicted by docking.A long equilibrium simulation was conducted to validate the structure of the complex.The results show that GSH is most commonly observed in three main pathways,one of which is more important than the other two.In addition,DCM was observed to escape along a unique pathway.The key residues and protein helices of each pathway were identified.The results can provide a theoretical foundation for the subsequent dissociation mechanism of DCM dehalogenase.

Temperature-Induced Unfolding Pathway of Staphylococcal Enterotoxin B:Insights from Circular Dichroism and Molecular Dynamics Simulation

In this study,circular dichroism(CD)and molecular dynamics(MD)simulation were used to investigate the thermal unfolding pathway of staphylococcal enterotoxin B(SEB)at temperatures of 298–371 and 298–500 K,and the relationship between the experimental and simulation results were explored.Our computational findings on the secondary structure of SEB showed that at room temperature,the CD spectroscopic results were highly consistent with the MD results.Moreover,under heating conditions,the changing trends of helix,sheet and random coil obtained by CD spectral fitting were highly consistent with those obtained by MD.In order to gain a deeper understanding of the thermal stability mechanism of SEB,the MD trajectories were analyzed in terms of root mean square deviation(RMSD),secondary structure assignment(SSA),radius of gyration(R_(g)),free energy surfaces(FES),solvent-accessible surface area(SASA),hydrogen bonds and salt bridges.The results showed that at low heating temperature,domain Ⅰ without loops(omitting the mobile loop region)mainly relied on hydrophobic interaction to maintain its thermal stability,whereas the thermal stability of domain Ⅱ was mainly controlled by salt bridges and hydrogen bonds.Under high heating temperature conditions,the hydrophobic interactions in domain Ⅰ without loops were destroyed and the secondary structure was almost completely lost,while domain Ⅱ could still rely on salt bridges as molecular staples to barely maintain the stability of the secondary structure.These results help us to understand the thermodynamic and kinetic mechanisms that maintain the thermal stability of SEB at the molecular level,and provide a direction for establishing safer and more effective food sterilization processes.

遗传算法在柔性臂控制中的应用

提出了一种双连杆柔性机械臂的控制方法。首先运用拉格朗日法建立双连杆柔性机械臂的动力学模型,并利用奇异摄动方法将柔性臂系统分解为慢变和快变子系统后,设计了组合控制器。对慢变子系统利用遗传算法确定两杆的PD控制参数,而对快变子系统采用最优H2综合策略设计控制器后,对柔性臂系统施加组合控制律。仿真结果表明了所设计控制器的有效性。

一种基于动模态分解的翼型流动转捩预测新方法

考虑自由转捩的定常/非定常流动Navier-Stokes方程数值求解,对于翼型流动细节的精确模拟和气动力的精确预测均具有十分重要的意义。采用动模态分解(DMD)方法进行流动稳定性分析,再结合e N方法,提出了一套适用于翼型绕流的转捩预测新方法,称为DMD/e N方法。相比于传统的线性稳定性分析方法,DMD方法不需要求解附面层方程和线性稳定性方程,也没有引入平行流假设,具有更好的理论适用性和算法鲁棒性。开展了NLF0416、S809和SD7003等翼型的转捩预测数值验证研究,通过与实验结果以及与传统的基于线性稳定性分析的e N方法的比较,验证了本文所发展的转捩预测新方法在预测翼型的定常流动和非定常流动转捩方面的正确性,也表明了该方法具有解决含层流分离泡的翼型绕流转捩预测的能力。

Kinetics analysis of decomposition of vanadium slag by KOH sub-molten salt method

A novel process was developed for the decomposition of vanadium slag using KOH sub-molten salt under ambient pressure, and the effects of reaction temperature, alkali-to-ore mass ratios, particle size, and stirring speed on vanadium and chromium extraction were studied. The results suggest that the reaction temperature and KOH-to-ore mass ratio are more influential factors for the extraction of vanadium and chromium. Under the optimal reaction conditions （temperature 180 °C, initial KOH-to-ore mass ratio 4：1, stirring speed 700 r/min, gas flow 1 L/min, and reaction time 300 min）, vanadium and chromium extraction rates can reach up to 95% and 90%, respectively. Kinetics analysis results show that the decomposing process of vanadium slag in KOH sub-molten salt can be well interpreted by the shrinking core model under internal diffusion control. The apparent activation energies for vanadium and chromium are 40.54 and 50.27 kJ/mol, respectively.

Non-isothermal thermal decomposition kinetics of high iron gibbsite ore based on Popescu method

The thermal decomposition kinetics of high iron gibbsite ore was investigated under non-isothermal conditions.Popescu method was applied to analyzing the thermal decomposition mechanism.The results show that the most probable thermal decomposition mechanism is the three-dimensional diffusion model of Jander equation,and the mechanism code is D3.The activation energy and pre-exponential factor for thermal decomposition of high iron gibbsite ore calculated by the Popescu method are 75.36 kJ/mol and 1.51×10-5 s-（-1）,respectively.The correctness of the obtained mechanism function is validated by the activation energy acquired by the iso-conversional method.Popescu method is a rational and reliable method for the analysis of the thermal decomposition mechanism of high iron gibbsite ore.

Carbon and nitrogen dynamics in early stages of forest litter decomposition as affected by nitrogen addition

The effects of nitrogen （N） availability and tree species on the dynamics of carbon and nitrogen at early stage of decomposition of forest litter were studied in a 13-week laboratory incubation experiment. Fresh litter samples including needle litter （Pinus koraiensis） and two types of broadleaf litters （Quercus mongolica and Tilia amurensis） were collected from a broadleaf-korean pine mixed forest in the northern slope of Changbai Mountain （China）. Different doses of N （equal to 0, 30 and 50 kg.ha^-1yr^-1, respectively, as NH4NO3） were added to litter during the experiment period. The litter decomposition rate expressed as mass loss and respiration rate increased significantly with increasing N availability. The mass loss and cumulative CO2-C emission were higher in leaf litter compared to that in needle litter. The dis- solved organic Carbon （DOC） concentrations in litter leachate varied widely between the species, but were not greatly affected by N treatments. Regardless of the N addition rate, both N treatments and species had no significant effect on dissolved organic N （DON） concentrations in litter leachate. About 52-78% of added N was retained in the litter. The percentage of N retention was positively correlated （R^2=0.9 1, p〈0.05） with the litter mass loss. This suggested that a forest floor with easily decomposed litter might have higher potential N sink strength than that with more slowly decomposed litter.

Properties and characterization of 1-methy-4,5-dinitroimidazole

X-ray diffraction （XRD）, differential scanning calorimeter （DSC） and impact sensitivity instrument were used to characterize the properties of 1-Methyl-4, 5-dinitroimidazole （MDNI）. Furthermore, specific heat capacity, thermal kinetic parameters, thermal decomposition reaction rate constant, critical explosion temperature and the drop height for impact initiation of MDNI were calculated and analyzed. The results show that MDNI is well-crystallized. The melting point of MDNI is about 74 ℃, and the specific heat capacity of MDNI is 9. 314 4 J/（g · K） and 10. 596 0 J/（g · K） when the temperature is 60 ℃ and 90 ℃, respectively. The apparent activation energy and pre-exponential factor of MDNI are calculated as 81.62 kJ/mol and 6. 78×10^7 s^-1 , respectively. The relationship between thermal decomposition reaction rate constant of MDNI and temperature is logk=7.83-4268.11/T. The critical temperature of MDNI thermal explosion is 234. 86℃. The drop height for impact initiation of MDNI is 95.3 cm.

Oscillations of the Solutions of Hyperbolic Partial Differential Equations of Neutral Type

In this paper, oscillatory properties of solutions of certain nonlinear hyperbolic partial differential equations are investigated and a series of sufficient conditions for oscillations of the equations are established. The results fully indicate that the oscillations are caused by delay.

Signal de-noising method based on wavelet decomposition

A noise reduction method for infrared detector output signal is studied during dynamic calibration of thermocou- pie. Firstly, the deficiency of the classical filter method is analyzed and the application of the wavelet analysis is introduced for signal de-noising during the dynamic testing. Secondly, the theoretical basis of wavelet analysis, the choice of wavelet base and the determination of decomposed series and threshold are analyzed. Finally, the de-noising experiment for infrared detector signal is carried out on the Matlab platform. The results indicate the proposed wavelet de-noising method is effective to remove fixed frequency and high-frequency noise; furthermore, good synchronization is achieved between the de-noised signal and the useful signal components in the original signal, which is of great significance to thermocouple modeling analys- is.

Enantio-selective preparation of (S)-1-phenylethanol by a novel marine GDSL lipase MT6 with reverse stereo-selectivity

We previously functionally characterized a novel marine microbial GDSL lipase MT6 and identified that the stereo-selectivity of MT6 was opposite to that of other common lipases in trans-esterification reactions.Herein,we have investigated the use of MT6 in stereo-selective biocatalysis through direct hydrolysis reactions.Notably,the stereo-selectivity of MT6 was also demonstrated to be opposite to that of other common lipases in hydrolysis reactions.Parameters,including temperature,organic co-solvents,pH,ionic strength,catalyst loading,substrate concentration,and reaction time,affecting the enzymatic resolution of racemic 1-phenylethyl acetate were further investigated,with the e.e.of the final（S）-l-Phenylethanol product and the conversion being 97%and 28.5%,respectively,after process optimization.The lengths of side chains of 1-phenylethyl esters greatly affected the stereo-selectivity and conversion during kinetic resolutions.MT6 is a novel marine microbial GDSL lipase exhibiting opposite stereo-selectivities than other common lipases in both trans-esterification reactions and hydrolysis reactions.