Prediction of Coefficient of Restitution for Impact Elastoplastic Spheres Considering Finite Plate Thickness

Collisions between objects are a relatively common phenomenon in nature.Analyses of collision processes can greatly contribute to solving problems such as impact-rub faults and particle impacts.The coefficient of restitution is a critical parameter in the analysis of collision processes.Many experiments have shown that the coefficient of restitution is closely related to the plate thickness,and the smaller the plate thickness,the more inaccurate the coefficient of restitution predicted by the existing model,which seriously affects the process of collision analysis.To remedy this shortcoming,this paper proposes a plate thickness influence factor with the ratio of sphere diameter to plate thickness as the variable.The plate thickness influence factor can optimize the coefficient of restitution model to effectively predict the coefficient of restitution of impacting elastoplastic spheres with finite plate thickness.Finally,the validity of the new model is verified using a large amount of experimental data.

Time Synchronous Averaging Based on Cross-power Spectrum

Periodic components are of great significance for fault diagnosis and health monitoring of rotating machinery.Time synchronous averaging is an effective and convenient technique for extracting those components.However,the performance of time synchronous averaging is seriously limited when the separate segments are poorly synchronized.This paper proposes a new averaging method capable of extracting periodic components without external reference and an accurate period to solve this problem.With this approach,phase detection and compensation eliminate all segments'phase differences,which enables the segments to be well synchronized.The effectiveness of the proposed method is validated by numerical and experimental signals.

One-Step Preparation of Green Fabric for Continuous Antibacterial Applications

Polypropylene(PP)scaffolds are the most commonly used biomedical scaffolds despite their disadvan-tages,which include problems with adhesion,infection,and inflammatory responses.Here,we report on the successful development of a facile one-step method to fabricate a series of novel triclosan poly-dopamine polypropylene(TPP)composite scaffolds and thereby effectively improve the biocompatibility and long-term antibacterial properties of PP scaffolds.The antibacterial triclosan can effectively interact with dopamine during biocompatible polydopamine formation on the PP scaffold by one-step green fab-rication.Thanks to the sustained release of triclosan from the biocompatible polydopamine coating,a 5mm×5mm sample of TPP-coated scaffold made with a triclosan concentration of 8 mg-mL^(-1)(referredto herein as TPP-8)exhibited a continuous antibacterial effect against both Escherichia coli(E.coli)and Staphylococcus aureus(S.aureus)for more than 15d,at maximum antibacterial volumes of 2 and 5mL,respectively.Our study establishes a new direction for facile long-term antibacterial studies for medical applications.

Innovations of Agricultural Scientific Research Institutions in Management of Special Materials

In recent years,the Ministry of Agriculture has increased input in agricultural scientific research projects.As a result,the procurement amount and quantity of special materials are increasing gradually,and the management of special materials becomes more standardized.In order to do well in management of special materials,the authors made exploration and thinking about further strengthening management of special materials in combination with actual conditions,including establishing regulations and systems,enhancing procurement process,strengthening requisition and safekeeping,and reinforcing general ledger management of special materials.

基于宽频振动的燃气轮机叶片断裂故障识别特征与辨识方法

针对燃气轮机动叶片断裂故障难以及时、有效告警与识别的技术难关开展了研究。从叶片断裂故障机理出发,分析了不平衡转子对尾流压力的调制作用,建立了叶片激振力模型和激振力作用下机匣的强迫振动响应模型,求解了动叶片断裂激励下的宽频振动响应规律。在此基础上,构建了叶片断裂故障敏感特征并提出了基于改进K近邻(OKNN)的故障告警模型,实现叶片断裂故障的及时告警分析。进一步提出了叶片断裂故障定位参数,通过各级叶片特征参数的对比实现断裂故障的精准定位。综合以上研究,构建了宽频振动特征驱动的燃气轮机叶片断裂故障辨识方法,并通过某型燃气轮机实测案例验证了故障敏感特征及辨识方法的有效性。

Heavy metals potentially drive co-selection of antibiotic resistance genes by shifting soil bacterial communities in paddy soils along the middle and lower Yangtze River

Heavy metals(HMs)and antibiotic resistance have become serious environmental problems affecting soil and human health.Soil microorganisms play key roles in pollutant degradation and biogeochemical cycling processes;however,the interactions among HMs,soil microbial communities,and antibiotic resistance genes(ARGs)in agricultural soils remain unclear.Using quantitative real-time polymerase chain reaction and NovaSeq sequencing,we evaluated heavy metal contents,abundances of ARGs,soil bacterial community structure and functions,and their correlations in paddy soils at 43 sampling sites along the middle and lower reaches of the Yangtze River,central and eastern China.Our results showed the co-occurrence of HMs,ARGs,and HM resistance genes across all paddy soils.Additionally,significant positive associations were detected between HMs and resistance genes.Cadmium,czcA,and int1 were positively correlated with bacterial community diversity.The Mantel test showed that bacterial community composition and functions were significantly associated with HMs and resistance genes,such as Cd,Cr,Zn,copA,czcA,int1,and sul1.Moreover,HMs and ARGs were the major factors shaping soil bacterial communities;thus,HMs triggered proliferation of HM and antibiotic resistances by influencing the mobile genetic element(int1)and soil microbial communities.Our study revealed that HMs potentially drive the co-selection of ARGs by shifting soil bacterial community structure and functions,thereby increasing the potential risks to human health as well as ecological environment in the paddy soils along the middle and lower reaches of the Yangtze River.

Empirical prediction of hydraulic aperture of 2D rough fractures:a systematic numerical study

This study aims to propose an empirical prediction model of hydraulic aperture of 2D rough fractures through numerical simulations by considering the influences of fracture length,average mechanical aperture,minimum mechanical aperture,joint roughness coefficient(JRC)and hydraulic gradient.We generate 600 numerical models using successive random additions(SRA)algorithm and for each model,seven hydraulic gradients spanning from 2.5×10^(-7)to 1 are considered to fully cover both linear and nonlinear flow regimes.As a result,a total of 4200 fluid flow cases are simulated,which can provide sufficient data for the prediction of hydraulic aperture.The results show that as the ratio of average mechanical aperture to fracture length increases from 0.01 to 0.2,the hydraulic aperture increases following logarithm functions.As the hydraulic gradient increases from 2.5×10^(-7)to 1,the hydraulic aperture decreases following logarithm functions.When a relatively low hydraulic gradient(i.e.,5×10^(-7))is applied between the inlet and the outlet boundaries,the streamlines are of parallel distribution within the fractures.However,when a relatively large hydraulic gradient(i.e.,0.5)is applied between the inlet and the outlet boundaries,the streamlines are disturbed and a number of eddies are formed.The hydraulic aperture predicted using the proposed empirical functions agree well with the calculated results and is more reliable than those available in the preceding literature.In practice,the hydraulic aperture can be calculated as a first-order estimation using the proposed prediction model when the associated parameters are given.

Digital twin model of gas turbine and its application in warning of performance fault

The digital twin-driven performance model provides an attractive option for the warn gas-path faults of the gas turbines.However,three technical difficulties need to be solved:(1)low modeling precision caused by individual differences between gas turbines,(2)poor solution efficiency due to excessive iterations,and(3)the false alarm and missing alarm brought by the traditional fixed threshold method.This paper proposes a digital twin model-based early warning method for gas-path faults that breaks through the above obstacles from three aspects.Firstly,a novel performance modeling strategy is proposed to make the simulation effect close to the actual gas turbine by fusing the mechanism model and measurement data.Secondly,the idea of controlling the relative accuracy of model parameters is developed.The introduction of an error module to the existing model can greatly shorten the modeling cycle.The third solution focuses on the early warning based on the digital twin model,which self-learns the alarm threshold of the warning feature of gas-path parameters using the kernel density estimation.The proposed method is utilized to analyze actual measured data of LM2500+,and the results verify that the new-built digital model has higher accuracy and better efficiency.The comparisons show that the proposed method shows evident superiority in early warning of performance faults for gas turbines over other methods.

The Scholar＇s Robe： Material Culture and Political Power in Early Modern China

This essay explores the history of the scholar＇s robe as a nexus of material culture and political power. It focuses on the controversial garment --called ren 衽-found pervasively in the Confucian canon and confirmed in archaeological findings. But for hundreds of years there have been disagreements and changes concerning which specific term is identified with which part of the robe, especially involving the use of ren in the scholar＇s robe. The bulk of my analysis deals with two prominent scholars＇ monographs on the robe： Huang Zongxi＇s Investigation of the Robe （Shenyi kao） and Jiang Yong＇s pointed rebuttal titled Mistakes in ＂Investigation of the R obe＂ （ Shenyi kao wu）. The intellectual and political configurations of both works are analyzed in depth in order to contrast two options of cultural identity： Chinese superiority versus cosmopolitan universalism.

A novel measurement method of temperature model for bioreactor

A novel measurement method of temperature model for bioreactor has been proposed.Temperature is the key parameter in monitoring the bioreactor operation.However,the system input signal of bioreactor is delayed,and model parameters are uncertain,so the output of temperature is non-steady-state.Many dynamic measurements are not steady so that it cannot be described by variables constant in time.In this paper,we adopt the monopulse signal as input so that the output of the bioreactor system is steady.This method has a powerful ability to steady the output of the bioreactor.In view of the measurement results,it can be seen that the model dynamic measurement approaches the real process.The analytical expression of the monopulse response for the temperature model of the bioreactor is obtained.The novel measurement approach is simple and can be easily adopted by industry.