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An experimental research on surface oscillation of buoyant-thermocapillary convection in open cylindrical annuli

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Acta Mechanica Sinica 2014年第5期30卷 681-686页

作者： Li Zhang Li duan qi Kang National Microgravity Laboratory Institute of Mechanics Chinese Academy of Sciences

An experiment is carried out on the surface oscillation of buoyant-thermocapillary convection in an open cylindrical annulus. When the radial temperature difference AT reaches a critical value △Tc, a regular oscillation appears and soon disappears on the open surface, which varies when the liquid layer＇s thickness h and temperature difference △T are varied. With growth of △T, dominant frequency of the visible oscillation will grow too but is found within certain frequencies. Driving forces, buoyance and thermocapillarity, are responsible for this phenomanon and the ＂balance＂ point is considered to exist when h is between 4.5-5.0 mm. Surface oscillation region is also found restricted within a narrow gap when Bo is smaller than 3.7.

关键词： Cylindrical annulus Buoyant-thermocapillary convection Surface oscillation Critical temperature differ- ence

Non-covalently Functionalized Graphene Oxide-Based Coating to Enhance Thermal Stability and Flame Retardancy of PVA Film

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Nano-Micro Letters 2018年第3期10卷 11-23页

作者： Wenhua Chen Pengju liu Lizhen Min Yiming Zhou Yuan liu qi Wang Wenfeng duan State Key Laboratory of Polymer Materials Engineering Polymer Research Institute of Sichuan University State Key Laboratory of Special Functional Waterproof Materials Beijing Oriental Yuhong Waterproof Technology Co.Ltd.

The synergistic effect of conventional flame-retardant elements and graphene has received extensive attention in the development of a new class of flame retardants. Compared to covalent modification, the noncovalent strategy is simpler and expeditious and entirely preserves the original quality of graphene. Thus, non-covalently functionalized graphene oxide(FGO) with a phosphorus–nitrogen compound was successfully prepared via a one-pot process in this study. Polyethyleneimine and FGO were alternatively deposited on the surface of a poly(vinyl alcohol)(PVA) film via layer-by-layer assembly driven by electrostatic interaction, imparting excellent flame retardancy to the coated PVA film. The multilayer FGO-based coating formed a protective shield encapsulating the PVA matrix, effectively blocking the transfer of heat and mass during combustion. The coated PVA has a higher initial decomposition temperature of about 260 °C and a nearly 60% reduction in total heat release than neat PVA does. Our results may have a promising prospect for flame-retardant polymers.

关键词： Graphene Non-covalent functionalization Layer-by-layer Flame retardant Poly(vinyl alcohol)(PVA)

Study on propellant management device in plate surface tension tanks

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Acta Mechanica Sinica 2021年第10期37卷 1498-1508,I0001页

作者： Shangtong Chen Li duan qi Kang Key Laboratory of Microgravity Institute of MechanicsChinese Academy of SciencesBeijing100190China School of Engineering Sciences University of Chinese Academy of SciencesBeijing100049China

Surface tension tanks exploit the liquid surface tension in liquid transport and gas–liquid separation to provide gas-free propellant for the thruster. High transport efficiency of deflectors can ensure liquid relocation in the microgravity environment within a short period of time, which is helpful for providing gas-free propellant. This paper explores transport efficiency of deflectors through drop tower experiments and numerical simulations with the volume of fluid method. The experimental and numerical results show that both the liquid flow speed and the mass flow rate along deflectors increase as the widths of deflectors increase. Besides, a new type of propellant management device, which consists of four deflectors and four anti-sloshing baffles, is verified with numerical simulations and drop tower experiments. Moreover, long-term conditions are predicted by using similarity theories. These results can provide important references for the design of plate tanks.

关键词： Surface tension tank Capillary driven flow Drop tower Volume of fluid method

Two-dimensional launch window method to search for launch opportunities of interplanetary missions

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Chinese Journal of Aeronautics 2020年第3期33卷 965-977页

作者： Junhong duan Yuefeng liu Air and Missile Defense College Air Force Engineering UniversityXi’an 710051China Science and Technology on Electro-optic Control Laboratory Luoyang 471000China

Accurate and highly efficient approaches to obtain mission opportunities are still the goals of mission planners of interplanetary *** search for launch opportunities not only determines the specified launch window of the mission but also presents the performance requirements for the interplanetary probe and its launch *** effective method, namely the two-dimensional launch window method, is developed from a completely new perspective to determine all the launch opportunities of the mission in this *** a fixed launch time,the method to determine all the time windows in the dimension of Time-of-Flight(TOF) is firstly proposed and these time windows represent all the launch opportunities for the given launch *** then, the two-dimensional launch window method is proposed, which computes the time windows in both the launch time and TOF dimensions to achieve all launch opportunities of the *** examples are provided to demonstrate the accuracy and high efficiency of the *** with the widely-used pock-chop plot method, the proposed method reduces the computational time by two orders of magnitude for the same search precision, and thus is especially suitable for the cases involving rapid, high-precision, and/or large-scale searches for mission opportunities.

关键词： Interplanetary mission Launch opportunity Pock-chop plot Rendezvous Time-of-flight

缺血性脑卒中铁死亡特征基因NFE2L2的鉴定与验证

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中国组织工程研究 2025年第7期29卷 1466-1474页

作者：王咪马书杰刘杨齐瑞上海中医药大学附属岳阳中西医结合医院康复医学科上海市200437 上海中医药大学上海市201203 上海市第二康复医院上海市200431

背景:铁死亡与缺血性脑卒中的发病密切相关,靶向铁死亡是一种治疗缺血性脑卒中有前景的方案,但具体调控靶点尚不明确。目的:通过生物信息学和机器学习方法筛选缺血性脑卒中铁死亡相关特征基因,并通过细胞实验进行验证,探讨铁死亡在缺血... 详细信息

背景:铁死亡与缺血性脑卒中的发病密切相关,靶向铁死亡是一种治疗缺血性脑卒中有前景的方案,但具体调控靶点尚不明确。目的:通过生物信息学和机器学习方法筛选缺血性脑卒中铁死亡相关特征基因,并通过细胞实验进行验证,探讨铁死亡在缺血性脑卒中的作用。方法:基于GEO数据库和FerrDb数据库选取符合条件的缺血性脑卒中相关数据集和铁死亡表达数据集,通过t检验筛选铁死亡相关差异基因。对铁死亡相关差异基因进行GO功能富集分析与KEGG信号通路富集分析。通过PPI网络分析和机器学习筛选缺血性脑卒中铁死亡的特征基因,利用ROC分析和GSEA分析探究特征基因的准确性和生物功能。然后进行细胞实验,将HT22细胞分为对照组与缺血性脑卒中组,对照组不作任何干预,缺血性脑卒中组加入0.1 mol/L的H_(2)O_(2)干预24 h诱导细胞氧化应激和铁死亡,通过实时荧光定量RT-PCR和Western Blot验证铁死亡的发生和特征基因表达。结果与结论:(1)共获取45个铁死亡相关差异基因,GO和KEGG富集分析发现差异基因与氧化应激、自噬、铁死亡、脂肪细胞因子信号通路和线粒体代谢密切相关。(2)通过PPI网络中的MCODE插件和cytoHubba插件与机器学习中的LASSO算法和SVM-RFE算法共鉴定出1个铁死亡特征基因核因子E2相关因子2(nuclear factor erythroid 2-related factor 2,NFE2L2)。(3)对NFE2L2进行ROC曲线分析,发现在训练集和验证集中构建的诊断预测模型具有良好的准确性与特异性;对NFE2L2进行GSEA分析,发现特征基因通过免疫、炎症反应、氨基酸代谢及神经因子调控等方面参与缺血性脑卒中发病机制的调控。(4)细胞实验的RT-PCR和Western Blot分析表明,与对照组对比,缺血性脑卒中组中的酰基辅酶A合成酶长链家族成员4 mRNA和蛋白表达水平显著增高(P<0.05),谷胱甘肽过氧化物酶4 mRNA和蛋白表达水平显著降低(P<0.05);与对照组对比,缺血性脑卒中组中特征基因NFE2L2 mRNA和蛋白表达水平显著增高(P<0.05)。(5)上述结果证实,缺血性脑卒中与铁死亡密切相关,靶向特征基因NFE2L2可以为研究和治疗缺血性脑卒中提供一定的思路与方向。

关键词：缺血性脑卒中铁死亡生物信息学 HT22细胞机器学习特征基因细胞实验 NFE2L2 ASCL4 GPX4

Quantile Regression under Local Misspecification

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Acta Mathematicae Applicatae Sinica 2020年第4期36卷 790-802页

作者： Xiao-gang duan qi-hua WANG School of Statistics Beijing Normal UniversityBeijing 100875Chin Academy of Mathematics and System Science Chinese Academy of SciencesBeijing 100190China

The frequentist model averaging(FMA)and the focus information criterion(FIC)under a local framework have been extensively studied in the likelihood and regression setting since the seminal work of Hjort and Claes kens in *** inconvenience,however,of the existing works is that they usually require the involved criterion function to be twice differentiable which thus prevents a direct application to the case of quantile regression(QR).This as well as some other intrinsic merits of QR motivate us to study the FIC and FMA in a locally misspecified linear QR ***,we derive in this paper the explicit asymptotic risk expression for a general submodel-based QR estimator of a focus *** based on this asymptotic result,we develop the FIC and FMA in the current *** theoretical development depends crucially on the convexity of the objective function,which makes possible to establish the asymptotics based on the existing convex stochastic process *** studies are presented to illustrate the finite sample performance of the proposed *** low birth weight data set is analyzed.

关键词： frequentist model averaging focus information criterion local framework quantile regression

Graphene-based vertical thin film transistors

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Science China(Information Sciences) 2020年第10期63卷 42-53页

作者： Liting liu Yuan liu Xiangfeng duan Key Laboratory for Micro-Nano Optoelectronic Devices of Ministry of Education School of Physics and ElectronicsHunan University Department of Chemistry and Biochemistry University of California

Vertical field effect transistors(VFETs), where the channel material is sandwiched between source-drain electrodes and the channel length is simply determined by its body thickness, have attracted considerable interest for high performance electronics owning to their intrinsic short channel length. To enable the effective gate modulation and current switching behavior, the electrode of conventional VFET is largely based on perforated metals, in which the gate electrical field could penetrate through. Recently,with the emerge of graphene, a new type of graphene based VFETs has been developed. With finite density of states and the weak electrostatic screening effect, graphene exhibits a field-tunable work-function and partial electrostatic transparency, it can thus function as an "active" contact with tunable graphene-channel junction, enabling entirely new transistor functions or higher device performance not previously *** this review, we discuss the research progresses of graphene-based VFET, including the its basic device structure, carrier transport mechanism, device performance and novel properties demonstrated.

关键词： graphene electrode vertical transistors thin film transistors van der Waals heterostructures

Adaptive fuzzy backstepping control for attitude stabilization of flexible spacecraft with signal quantization and actuator faults

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Science China(Information Sciences) 2021年第5期64卷 135-150页

作者： qiuhong liu Ming liu Guangren duan Research Institute of Intelligent Control Systems Harbin Institute of Technology Research Center of Satellite Technology Harbin Institute of Technology Center for Control Theory and Guidance Technology Harbin Institute of Technology

In this study, the fault-tolerant attitude control of flexible spacecraft is investigated over digital communication channels, where a uniform quantizer is considered with respect to the sensor signals and controller indexes. Further, an adaptive fuzzy backstepping control strategy has been developed for the considered attitude stabilization issue, where the adaptive fuzzy logic method is used to approximate the rigid-flexible coupled nonlinearity of the spacecraft. In this design, the online adjusting quantizer parameters are injected into the controller gains to simultaneously compensate for the quantization errors and timevarying actuator faults. In the proposed control method, the attitude stabilization task is achieved in the presence of external disturbances, time-varying actuator faults, and signal quantization. Finally, the practical examples are compared to demonstrate the effectiveness of the proposed control strategy.

关键词： fault-tolerant control attitude stabilization signal quantization adaptive fuzzy control backstepping control

In Situ Coupling Strategy for Anchoring Monodisperse Co_9S_8 Nanoparticles on S and N Dual?Doped Graphene as a Bifunctional Electrocatalyst for Rechargeable Zn–Air Battery

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Nano-Micro Letters 2019年第1期11卷 64-77页

作者： qi Shao Jiaqi liu qiong Wu qiang Li Heng?guo Wang Yanhui Li qian duan School of Materials Science and Engineering Changchun University of Science and Technology

An in situ coupling strategy to prepare Co_9S_8/S and N dual?doped graphene composite(Co_9S_8/NSG) has been proposed. The key point of this strategy is the function?oriented design of organic compounds. Herein, cobalt porphyrin derivatives with sulfo groups are employed as not only the coupling agents to form and anchor Co_9S_8 on the graphene in situ, but also the heteroatom?doped agent to generate S and N dual?doped graphene. The tight coupling of multiple active sites endows the composite materials with fast electrochemical kinetics and excellent stability for both oxygen reduction reaction(ORR) and oxygen evolution reaction(OER). The obtained electrocatalyst exhibits better activity parameter(ΔE = 0.82 V) and smaller Tafel slope(47.7 mV dec^(-1) for ORR and 69.2 mV dec^(-1) for OER) than commercially available Pt/C and RuO_2. Most importantly, as electrocatalyst for rechargeable Zn–air battery, Co_9S_8/NSG displays low charge–discharge voltage gap and outstanding long?term cycle stability over 138 h compared to Pt/C–RuO_2. To further broaden its application scope, a homemade all?solid?state Zn–air battery is also prepared, which displays good charge–discharge performance and cycle performance. The function?oriented design of N_4?metallomacrocycle derivatives might open new avenues to strategic construction of high?performance and long?life multifunctional electrocatalysts for wider electro?chemical energy applications.

关键词： In situ coupling strategy Porphyrin derivate Doped graphene Metal sulfide Bifunctional electrocatalyst Rechargeable Zn–air battery