AWK-TIS:An Improved AK-IS Based on Whale Optimization Algorithm and Truncated Importance Sampling for Reliability Analysis

In this work,an improved active kriging method based on the AK-IS and truncated importance sampling(TIS)method is proposed to efficiently evaluate structural reliability.The novel method called AWK-TIS is inspired by AK-IS and RBF-GA previously published in the literature.The innovation of the AWK-TIS is that TIS is adopted to lessen the sample pool size significantly,and the whale optimization algorithm(WOA)is employed to acquire the optimal Krigingmodel and themost probable point(MPP).To verify the performance of theAWK-TISmethod for structural reliability,four numerical cases which are utilized as benchmarks in literature and one real engineering problem about a jet van manipulate mechanism are tested.The results indicate the accuracy and efficiency of the proposed method.

Melatonin alters the secondary metabolite profile of grape berry skin by promoting VvMYB14-mediated ethylene biosynthesis

The interplay between melatonin and ethylene in the regulation of fruit metabolism and the underlying molecular mechanism of this interplay remain largely unclear.Here,widely targeted metabolomics analysis revealed a total of 464 metabolites present in berry skin.Among them,27 significantly differentially accumulated metabolites(DAMs)were produced in response to melatonin treatment in the presence or absence of 1-MCP.Most of the DAMs were secondary metabolites,including flavonoids,phenolic acids,stilbenes,and flavonols.Additionally,the accumulation of 25 DAMs was regulated by melatonin via ethylene.RNA-seq analysis indicated that melatonin primarily regulated the pathways of plant hormone signal transduction and secondary metabolite biosynthesis via ethylene.Gene-metabolite association analysis showed that melatonin regulated the expression of the VvSTS1,VvF3H,VvLAR2,and VvDFR genes,suggesting that these genes may play key roles in regulating secondary metabolites in the skin;additionally,VvMYB14 and VvACS1 were suggested to be involved in the regulation of secondary metabolites.Further experiments revealed that melatonin induced the expression of VvMYB14 and that VvMYB14 increased ethylene production by transcriptionally activating VvACS1,thereby affecting the accumulation of secondary metabolites.Collectively,melatonin promotes ethylene biosynthesis and alters secondary metabolite accumulation through the regulation of VvACS1 by VvMYB14.

A Preliminary Study on the Regularity of Outbreak of Thrips in Asparagus-bean Interplanting Fields

[Objectives]This study was conducted to clarify the composition and occurrence regularity of thrips in asparagus-soybean intercropping fields.[Methods]The species and occurrence dynamics of thrips in asparagus-bean intercropping fields in Luquan District of Shijiazhuang were investigated.[Results]There were 7 species of thrips in this area,namely,tobacco thrips[Thrips alliorum(Priesner)],western flower thrips[Frankliniella occidentalis(Pergande)],Scolothrips takahashii Priesner,Megalurothrips usitatus(Bagrall),Sussericothrips melilotus Han and Aeolothrips fasciatus.As the dominant species,tobacco thrips had two peak outbreaks in late June and late September,and maintained a high quantity level for a long time.Other thrips had fewer population and different occurrence time,but were greatly affected by temperature,humidity and host crop species.[Conclusions]This study provides a theoretical basis for the forecast and comprehensive control of thrips in North China.

A Method of Human-Like Compliant Assembly Based on Variable Admittance Control for Space Maintenance

On-orbit assembly has become a crucial aspect of space operations,where the manipulator frequently and directly interacts with objects in a complex assembly process.The traditional manipulator control has limitations in adapting to diverse assembly tasks and is vulnerable to vibration,leading to assembly failure.To address this issue,we propose a human-like variable admittance control method based on the variable damping characteristics of the human arm.By collecting the velocity and contact force of human arm operations in assembly,we analyze the damping change of human arm and establish the active compliance model based on S-type damping variation rule in assembly.Furthermore,3 passive contact models are proposed between the end of the human arm and the environment:one-sided bevel contact,both sides bevel contact,and pin-hole contact.On the basis of these active and passive models,a typical space assembly task for a robot is designed,and a human-like variable admittance controller is established and simulated.Finally,we build a ground verification platform and complete different assembly tasks,thereby successfully verifying the safety,robustness,and adaptability of the human-like variable admittance control method.

Spatial distribution of bacterial community in EGSB reactor treating synthetic sulfate-containing wastewater at low organic loading rate

Given that the consumption of organic substances entails costly biodesulfurization,the characteristics of the bacterial community in a reactor should be determined to increase the desulfurizing rate under low organic loading condition.In this study,the bacterial community distribution in the expanded granular sludge bed reactor used to treat sulfate-containing wastewater with low organic loading rate was determined by polymerase chain reaction-denaturing gradient gel electrophoresis(PCRDGGE)and 16S rDNA clone library analyses.DGGE results showed that the predominant bacteria were stable and accounted for*90%sulfate removal efficiency.Differences in band positions and intensities indicated that the distribution and abundance of bacteria were affected by their positions in the reactor.Typical bands were identified in the bacterial community comprising Desulfovibrio,Desulfomicrobium,Thiomonas,Acinetobacter,Bacteroidetes,and Chloroflexi.Their functions in the reactor were also discussed.The possible links between the functional and microbial responses were also investigated based on the characteristic and spatial distribution of each bacterium in consortium.

Conversion of methane through dielectric-barrier discharge plasma

Methane coupling to produce C2 hydrocar-bons through a dielectric-barrier discharge(DBD)plasma reaction was studied in four DBD reactors.The effects of high voltage electrode position,different discharge gap,types of inner electrode,volume ratio of hydrogen to methane and air cooling method on the conversion of methane and distribution of products were investigated.Conversion of methane is obviously lower when a high voltage electrode acts as an outer electrode than when it acts as an inner electrode.The lifting of reaction temper-ature becomes slow due to cooling of outer electrode and the temperature can be controlled in the expected range of 60℃-150℃for ensuring better methane conversion and safe operation.The parameters of reactors have obvious effects on methane conversion,but it only slightly affects distribution of the products.The main products are ethyl-ene,ethane and propane.The selectivity of C2 hydrocar-bons can reach 74.50%when volume ratio of hydrogen to methane is 1.50.

Progress and Development Trend of Space Intelligent Robot Technology

Since space intelligent robots are not restricted by physiological conditions,it is an attractive choice for the development of automation technology to use them for space exploration and utilization.It is currently the key development direction of the major space powers over the world.This paper first investigates the robotic manipulators and humanoid robot systems for space station applications and reviews theories and methods for robots to achieve large-range stable motion and intelligent dexterous manipulation.Then,the intelligent robot systems for on-orbit satellite maintenance are reviewed,and the related technologies of multirobot collaboration are analyzed.Finally,we investigate the intelligent robot systems for on-orbit assembly of large-scale spatial structures and summarize the technologies of modular assembly and on-orbit manufacture.Overall,this paper reviews the technological progress and development trends of space robots,which provides a good reference for further technical research in this field.