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Spectrum analysis of interval process model and its application in uncertain vibration analysis

Science China Technological Sciences 2024年第8期67卷 2549-2564页

作者： li jinwu JIANG Chao NI BingYu State Key Laboratory of Advanced Design and Manufacturing Technology for Vehicle College of Mechanical and Vehicle Engineering Hunan University

In recent years, the authors have extended the traditional interval method into the time dimension to develop a new mathematical tool called the “interval process model” for quantifying time-varying or dynamic uncertainties. This model employs upper and lower bounds instead of precise probability distributions to quantify uncertainty in a parameter at any given time point. It is anticipated to complement the conventional stochastic process model in the coming years owing to its relatively low dependence on experimental samples and ease of understanding for engineers. Building on our previous work, this paper proposes a spectrum analysis method to describe the frequency domain characteristics of an interval process, further strengthening the theoretical foundation of the interval process model and enhancing its applicability for complex engineering problems. In this approach, we first define the zero midpoint function interval process and its auto/cross-power spectral density(PSD) functions. We also deduce the relationship between the auto-PSD function and the auto-covariance function of the stationary zero midpoint function interval process. Next, the auto/cross-PSD function matrices of a general interval process are defined, followed by the introduction of the concepts of PSD function matrix and cross-PSD function matrix for interval process vectors. The spectrum analysis method is then applied to random vibration problems, leading to the creation of a spectrum-analysis-based interval vibration analysis method that determines the PSD function for the system displacement response under stationary interval process excitations. Finally, the effectiveness of the formulated spectrum-analysis-based interval vibration analysis approach is verified through two numerical examples.

关键词： interval process spectrum analysis power spectral density (PSD) time-varying uncertainty uncertain vibration analysis

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A novel imprecise stochastic process model for time-variant or dynamic uncertainty quantification

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Chinese Journal of Aeronautics 2022年第9期35卷 255-267页

作者： jinwu li Chao JIANG State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China

This paper proposes a novel model named as “imprecise stochastic process model” to handle the dynamic uncertainty with insufficient sample information in real-world problems. In the imprecise stochastic process model, the imprecise probabilistic model rather than a precise probability distribution function is employed to characterize the uncertainty at each time point for a time-variant parameter, which provides an effective tool for problems with limited experimental samples. The linear correlation between variables at different time points for imprecise stochastic processes is described by defining the auto-correlation coefficient function and the crosscorrelation coefficient function. For the convenience of analysis, this paper gives the definition of the P-box-based imprecise stochastic process and categorizes it into two classes: parameterized and non-parameterized P-box-based imprecise stochastic processes. Besides, a time-variant reliability analysis approach is developed based on the P-box-based imprecise stochastic process model,through which the interval of dynamic reliability for a structure under uncertain dynamic excitations or time-variant factors can be obtained. Finally, the effectiveness of the proposed method is verified by investigating three numerical examples.

关键词： Dynamic reliability analysis Epistemic uncertainty Imprecise random variable Imprecise stochastic process P-box model Time-variant uncertainty

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Uncertain eigenvalue analysis of the dielectric-filled waveguide by an interval vector finite element method

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Science China(Technological Sciences) 2022年第2期65卷 336-346页

作者： WANG ZhongHua JIANG Chao NI BingYu li jinwu ZHENG Jing YAO ZhongYang State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle EngineeringHunan UniversityChangsha 410082China

Eigenvalues of the dielectric-filled waveguide are of great importance to its transmission characteristic analysis and optimization design, which could be easily affected by spatially uncertain dielectric parameters. For the sake of quantifying their influence on eigenvalues of the dielectric-filled waveguide and overcoming the limitation of less samples, an interval vector finite element method(IVFEM) is proposed to acquire the lower and upper bounds of the eigenvalues with spatial uncertainty of the medium parameters. Firstly, the uncertain dielectric material properties are described by the interval field model and the corresponding interval Karhunen-Loève(K-L) approximate method. Secondly, by inserting the interval uncertainties into the constitutive relationship of the standard generalized eigenvalue equations of the dielectric-filled waveguide, an interval standard generalized eigenvalue equation is then formulated. At last, the lower and upper bounds of the eigenvalues are calculated according to the first-order perturbation method, which can be used to estimate the transmission properties of the waveguide efficiently. Three kinds of the dielectric-filled waveguides are analyzed by the proposed IVFEM and verified by Monte Carlo simulation method.

关键词： dielectric-filled waveguide eigenvalue spatial uncertainty interval vector finite element method

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Effect of wall-disruption on nutrient composition and in vitro digestion of camellia and lotus bee pollens

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Food Science and Human Wellness 2024年第3期13卷 1567-1577页

作者： Yuan Yuan Shun Zhong Zeyuan Deng Guangyan li jinwu Zhang Hongyan li State Key Laboratory of Food Science and Resources Nanchang UniversityNanchang 330047China Nanchang Tongxin Zichao Biological Engineering Co. Ltd.Nanchang 330052China

The nutrient digestion,absorption and biological activity of bee pollen may be limited due to the complex pollen ***,the effect of superfine grinding technology on the release of nutrients from bee pollen were investigated,and their antioxidant activities and in vitro digestion were explored in this *** showed that the content of nutrients in bee pollen increased after wall *** them,fat content increased by 22.55%-8.31%,protein content increased by 0.54%-4.91%,starch content increased by 36.31%-48.64%,soluble sugar content increased by 20.57%-29.67%,total phenolic acid content increased by 11.73%-86.98%and total flavonoids content increased by 14.29%-24.79%.At the same time,the antioxidant activity increased by 14.84%-46.00%.Furthermore,the active components such as phenolic compounds in the wall-disruption bee pollen were more readily to be released during the in vitro digestion,and easier to be absorbed because of their higher *** activities during in vitro digestion were also improved in walldisruption bee *** findings provide evidence that bee pollen wall disruption was suggested,thus,it is more conducive to exerting the value of bee pollen in functional foods.

关键词： Bee pollen Nutrients Wall disruption Phenolic compounds In vitro digestion

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Numerical simulation of aircraft arresting process with an efficient full-scale rigid-flexible coupling dynamic model

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Chinese Journal of Aeronautics 2024年第5期37卷 586-602页

作者： Haoyuan SHAO Daochun li Zi KAN Lanxi BI Zhuoer YAO jinwu XIANG School of Aeronautic Science and Engineering Beihang UniversityBeijing 100191China Tianmushan Laboratory Hangzhou 310023China

The arresting process of carrier-based aircraft is widely recognized as a challenging task,characterized by the highest accident rate among all carrier-based aircraft *** simulation plays a crucial role in assessing the intricate responses of the arresting process,favoring the design of carrier-based *** efficient and accurate rigid-flexible coupling model for analyzing the dynamic response of the arresting process is *** combining the dynamic characteristics of airframe,landing gear,arresting hook and arresting gear system,the rigid-flexible coupling dynamic model is established to reflect the relative motion of the coupling parts and arresting *** dynamic model is verified through simulations of landing gear landing drops and by comparing the arresting simulation results with corresponding data in the US military ***,simulations of the arresting process under different off-center distance and aircraft yaw angle are conducted to obtain the dynamic response of the aircraft during the arresting *** result indicates that the rigid-flexible coupling dynamic model proposed is effective for analyzing the arresting dynamics response of carrier-based *** axial force of the arresting cable on both sides of the hook engagement point,pitch and yaw angle of aircraft are inconsistent under yaw and off-center *** analysis method and obtained results provide valuable references for assessing the dynamic responses of carrier-based aircraft during arresting process and offer valuable in-sights in the design of carrier-based aircraft.

关键词： Carrier-based aircraft Deck landing Rigid-flexible coupling dynamic model Finite element method Dynamic analysis

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Non-random vibration analysis for general viscous damping systems

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Chinese Journal of Aeronautics 2019年第12期32卷 2655-2666页

作者： Chao JIANG Long liU jinwu li Bingyu NI State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body College of Mechanical and Vehicle Engineering Hunan University

The authors recently developed a kind of non-probabilistic analysis method, named as‘non-random vibration analysis’, to deal with the important random vibration problems, in which the excitation and response are both given in the form of interval process rather than stochastic process. Since it has some attractive advantages such as easy to understand, convenient to use and small dependence on samples, the non-random vibration analysis method is expected to be an effective supplement of the traditional random vibration theory. In this paper, we further extend the nonrandom vibration analysis into the general viscous damping system, and formulate a method to calculate the dynamic response bounds of a viscous damping vibration system under uncertain excitations. Firstly, the unit impulse response matrix of the system is obtained by using a complex mode superposition method. Secondly, an analytic formulation of the system dynamic response middle point and radius under uncertain excitations is derived based on the Duhamel’s integral, and thus the upper and lower response bounds of the system can be obtained. Finally, two numerical examples are investigated to demonstrate the effectiveness of the proposed method.

关键词： Complex mode Dynamic response bounds Interval process Random vibration Viscous damping system

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Bimolecular reduction of carbon dioxide: double synthons for alkynes trifunctionalization

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Science China Chemistry 2024年第3期67卷 841-847页

作者： Wenfang Xiong Xiaobin Tan Hongjian liu Baiyao Zhu jinwu Zhao Jianxiao li Chaorong Qi Huanfeng Jiang School of Pharmacy Guangdong Medical UniversityDongguan 523808China Key Lab of Functional Molecular Engineering of Guangdong Province School of Chemistry and Chemical EngineeringSouth China University of TechnologyGuangzhou 510640China

Carbon dioxide reduction, as a sustainable and versatile strategy for the access of chemical fuels, has attracted increasing attention and enormous efforts have been devoted to it in recent years. However, employing carbon dioxide as double synthons via bimolecular reduction remains challenging. Here, by leveraging the bimolecular reduction of carbon dioxide to carbonyl and methyl respectively, we describe a Pd-catalyzed trifunctionalization of alkynes with aryl iodide for the first time and showcase its advantages on the formation of various β-diketones and their application in the constructing of heterocyclic compounds with important biological activity, including pyrimidine, oxazole, pyrazole.

关键词： carbon dioxide bimolecular reduction trifunctionalization double synthons

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Design and optimization of the seed conveying system for belt-type highspeed corn seed guiding device

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International Journal of Agricultural and Biological Engineering 2024年第2期17卷 123-131页

作者： Yifei li Wenqi Zhou Chengcheng Ma Zhaohua Feng jinwu Wang Shujuan Yi Song Wang College of Engineering Northeast Agricultural UniversityHarbin 150030China College of Engineering Heilongjiang Bayi Agricultural UniversityDaqing 163000HeilongjiangChina Agricultural Engineering Department Qitaihe Vocational Technician CollegeQitaihe 154600HeilongjiangChina

Seeding is an important part of improving corn ***,seed guide tubes are mostly used as transport *** the existing seed guide tubes cannot meet the requirements or achieve the goal of fixing the seed falling trajectory.A seed collision phenomenon occurs ***,in response to the problems that the seeds and seed guide tube collide or bounce under high speed operation,which results in a lower sowing qualification rate and poor spacing uniformity,a seed receiving and conveying system comprising a belt-type high-speed corn seed guiding device was designed and optimized,to meet the needs of high-speed precision sowing operations and improve the spacing *** factors affecting the seed conveying performance were obtained by analyzing the mechanical properties of the seeds at various movement *** factors were the number of seed cavities between adjacent seeds,the forward speed,the height from the ground,and the installation *** factor simulation experiments were conducted by selecting the paddle spacing as the test factor and using the pass rate,reseeding rate,omission rate and coefficient of variation as the evaluation indexes to investigate the influence of the paddle spacing on the seed guide performance of the device and further determine the structural parameters of the paddle *** rotation combination tests of three factors and five levels were also conducted through bench *** the test outcomes were *** results indicated that the best results were obtained when the number of seed cavity intervals between adjacent seeds was 5.16,the installation angle was 79.40°,and the height from the ground was 31.84 *** this time,the qualified rate was 98.49%,the repeated sowing rate was 0.48%,the missed sowing rate was 1.03%,and the coefficient of variation was 6.80%.Experiments were used to validate the optimization results,and all of the obtained index data satisfied the criteria for accurate

关键词： corn high-speed sowing belt-type seed guide device test

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Design optimization and testing of a morphing leading-edge with a variable-thickness compliant skin and a closed-chain mechanism

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Chinese Journal of Aeronautics 2024年第7期37卷 285-300页

作者： Zhigang WANG Xiasheng SUN Yu YANG Wenjie GE Daochun li jinwu XIANG Panpan BAO Qi WU Andrea DA RONCH School of Aeronautical Science and Engineering Beihang UniversityBeijing 100191China National Key Laboratory of Strength and Structural Integrity Aircraft Strength Research Institute of ChinaXi’an 710065China School of Aeronautics and Astronautics Shanghai Jiao Tong UniversityShanghai 200240China School of Mechanical Engineering Northwestern Polytechnical UniversityXi’an 710072China Faculty of Engineering and Physical Sciences University of SouthamptonSouthampton SO171JBUK

Climate warming and the increased demand in air travels motivate the aviation industry to urgently produce technological *** of the most promising innovations is based on the smoothly continuous morphing leading-edge *** study proposes a two-step process for the design of a morphing leading-edge,including the optimization of the outer variable-thickness composite compliant skin and the optimization of the inner kinematic *** the compliant skin design,an optimization of the variable thickness composite skin is proposed based on a laminate continuity model,with laminate continuity constraint and other manufacturing *** laminate continuity model utilizes a guiding sequence and a ply-drop sequence to describe the overall stacking sequence of plies in different thickness regions of the complaint *** the inner kinematic mechanism design,a coupled four-bar linkage system is proposed and optimized to produce specific trajectories at the actuation points on the stringer hats of the compliant skin,which ensures that the compliant skin can be deflected into the aerodynamically optimal ***,a morphing leading-edge is manufactured and *** results are compared with numerical predictions,confirming the feasibility of the morphing leading-edge concept and the overall proposed design approach.

关键词： Optimization Design Morphing wing Compliant skin Kinematics Leading-edge Control surfaces

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Coupling metal-organic frameworks and wood-based carbon for water remediation

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Nano Research 2024年第6期17卷 5661-5669页

作者： Akhter Zia Manish Neupane Aidan McGlone Rui He Ruikun Xin Yifeng liu Qiangu Yan jinwu Wang ling li Zhiyong Cai Pei Dong Yingchao Yang Department of Mechanical Engineering University of MaineOronoME 04469USA Department of Mechanical and Aerospace Engineering University of MissouriColumbiaMO 65211USA Department of Mechanical Engineering George Mason UniversityFairfaxVA 22030USA Department of Civil and Environmental Engineering Rice UniversityHoustonTX 77005USA Department of Materials Science and NanoEngineering Rice UniversityHoustonTX 77005USA Forest Products Laboratory USDAMadisonWI 53726USA School of Forestry Resources University of MaineOronoME 04469USA

Fresh and clean water is highly demanded throughout the *** effectively address the need,nanomaterials enabled nanotechnology has been explored as a means of more efficient,reliable,and environmentally friendly approach towards water treatment *** concern in adopting nanomaterials is how to retrieve them from water body to avoid secondary *** this work,the earth abundant and sustainable wood,e.g.,basswood,was selected and carbonized into porous carbon as host skeleton,and metal-organic frameworks(MOFs),e.g.,MOF-199 with extremely high surface area,were grown throughout all channels in the porous basswood *** the traditional organic pollutant,methyl orange(MO),the combination of MOFs and basswood carbon(MOFs@carbon)demonstrates a remarkable adsorption capacity,which is 243%and 454%higher than basswood carbon and MOF-199,*** an outstanding adsorption performance originates from that the positively charged carbon pulls MO molecules close to carbon surface,leading to a high MO molecule concentration,and then the concentration gradient drives the MO molecules to be stored inside MOFs,functioning like *** findings highlight the potential application of coupled MOFs and biomass carbon in addressing water remediation.

关键词： metal-organic framework(MOF)-199 basswood carbon MOFs@carbon methyl orange

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