Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of mi...Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of microorganisms in aquatic ecosystems.To understand the influences of ecological floating beds on size-fractionated microorganisms,we investigated the community assembly and nitrogen metabolic characteristics of three size-fractionated microorganism groups in the ecological floating bed area,using 18S rDNA,16S rDNA metabarcoding,and metagenomic sequencing techniques.Firstly,we discovered substantial differences between size-fractionated groups in the diversity and compositions of both microeukaryotic and bacterial communities,as well as the influences of floating beds on specific groups.The floating beds appeared to provide more habitats for heterotrophs and symbiotes while potentially inhibiting the growth of certain phytoplankton(cyanobacteria).Secondly,we observed that microeukaryotic and bacterial communities were predominantly influenced by stochastic and deterministic processes,respectively,and they both exhibited distinct patterns across different size-fractionated groups.Notably,microeukaryotic community assembly demonstrated a greater sensitivity to ecological floating beds,as indicated by an increase in dispersal limitation processes.Finally,the nitrogen metabolism functional genes revealed that microbes associated with large-sized particles played a crucial role in dissimilatory nitrate reduction to ammonium(DNRA)and denitrification processes within the floating bed area,thereby facilitating the removal of excess nitrogen nutrients from the water.In contrast,freeliving microorganisms from small-sized groups were linked mainly to the genes involved in nitrogen assimilation and assimilatory nitrate reduction to ammonium(ANRA)processes.These findings help understand the impact of ecological floating beds on the diversity and functional characteristics of microorganism communities in different size-fractionated groups.展开更多
Soil microbiomes are significant for biodiversity,crucial for ecosystem functions,and vital for the health of various organisms.Nevertheless,the impacts of season and plant species shifts on soil microbial diversity a...Soil microbiomes are significant for biodiversity,crucial for ecosystem functions,and vital for the health of various organisms.Nevertheless,the impacts of season and plant species shifts on soil microbial diversity and community assembly are still poorly understood.This study explored soil bacterial,fungal,and protistan communities during summer and winter in a coastal wetland affected by Spartina alterniflora invasion and subsequent Cyperus malaccensis or Kandelia obovata restoration.The results showed that bacterial,fungal,and protistan diversity were 2.63%,40.3%,and 9.90%higher in winter than in summer,respectively.Plant species had a distinct impact on microbial diversity.Notably,K.obovata restoration significantly increased bacterial diversity,but decreased protistan diversity,with no effect on fungal diversity when compared to S.alterniflora invasion.Season and plant species both significantly influenced the community structure of bacteria,fungi,and protists.However,protistan community structure was more sensitive to season compared to the structure of bacterial and fungal communities.The complexity of co-occurrence networks within or among bacteria,fungi,and protists was higher in winter than in summer.Bacterial and protistan community assembly was primarily driven by stochastic processes,while fungal assembly was dominated by deterministic processes.Bacterial and protistan community assembly exhibited lower stochasticity in winter compared to summer,suggesting a more deterministic assembly of communities during winter.Our findings highlight the critical role of season and plant species in regulating microbial communities,revealing higher microbial diversity,network complexity,and determinism in community assembly during winter compared to summer in a subtropical coastal wetland.展开更多
phoD and pqqC gene occurrence in bacteria allows them to mobilize phosphorus(P)by mineralizing organic P(Po)and solubilizing inorganic P(Pi),respectively.Community characteristics of phoD-and pqqC-harboring bacteria(p...phoD and pqqC gene occurrence in bacteria allows them to mobilize phosphorus(P)by mineralizing organic P(Po)and solubilizing inorganic P(Pi),respectively.Community characteristics of phoD-and pqqC-harboring bacteria(phoD-and pqqC-HB,respectively)mediate P cycling.However,whether the microbial community assembly and keystone taxa of phoD-and pqqC-HB regulate P availability and distinct regulatory pathways between these two genes remain unclear.In this study,soil microbial community characteristics and P availability were investigated in four long-term(38-year)fertilization regimes:control with no fertilizer(CK),P fertilizer(PF),nitrogen(N)and P fertilizers(NP),and N fertilizer,P fertilizer,and manure(NPM).The N addition treatments(NP and NPM)significantly changed the community composition and increased the abundances of phoD-and pqqC-HB compared to the no-N addition treatments(CK and PF).Stochastic processes dominated the community assembly of both phoD-and pqqC-HB,and the relative contributions of stochasticity increased with N addition.Furthermore,the N addition treatments resulted in greater network complexity and higher abundances of keystone taxa of phoD-and pqqC-HB compared to those of the no-N addition treatments.The keystone taxa implicated in P cycling were also associated with carbon(C)and N cycling processes.Microbial community composition and assembly processes were the main factors driving labile Pi for phoD-HB,whereas keystone taxa contributed the most to labile Pi for pqqC-HB.These results emphasize that distinct mechanisms of phoD-and pqqC-HB regulate P availability under fertilization management and underline the significance of microbial community assembly and keystone taxa in soil ecological functions,offering fresh perspectives on comprehending the biological processes facilitated by microorganisms in enhancing soil quality.展开更多
Bacterial communities play a crucial role in permafrost biogeochemical cycling and ecosystem function maintenance.Bacterial interaction is one of the main factors in shaping soil bacterial communities.However,how woul...Bacterial communities play a crucial role in permafrost biogeochemical cycling and ecosystem function maintenance.Bacterial interaction is one of the main factors in shaping soil bacterial communities.However,how would bacterial interaction influence the bacterial communities in permafrost of the Qinghai-Tibet Plateau(QTP)remains largely unknown.Here we collected paired soil samples from both the active and permafrost layers of two typical QTP permafrost regions in October 2020 for Tuotuohe River(TTH)and May 2022 for Aerjin(ARJ),and investigated the bacterial communities and the role of interactions in structuring the bacterial community and its assembly process through amplicon sequencing of the 16S rRNA gene.Our study revealed distinct bacterial communities,with significant differences in the relative abundances of Proteobacteria(P<0.05),Acidobacteriota(P<0.001),Bacteroidota(P<0.05),and Planctomycetota(P<0.001)between the active layer and the permafrost layer.More importantly,we found that interspecies interactions,including both positive and negative associations,were strongly correlated with bacterial alpha-diversity and played a significant role in community variation and assembly process.Our findings also showed that the community assembly in both the active and permafrost layers was primarily driven by homogeneous selection of deterministic processes,with interspecies interactions accounting for more than 58%and 63%of all assembly mechanisms,respectively.This is the first study to quantify the contribution of bacterial interactions in shaping the bacterial community and its assembly process in permafrost of QTP,highlighting the importance of considering interspecies interactions in future modeling efforts.Our work also emphasizes the necessity of including interspecies interactions in microbial process projections to reduce uncertainty.展开更多
Odd-numbered and high-nuclearity coordination clusters are extremely rare,yet they represent an intriguing subclass lacking regular repeating building blocks and high structural symmetry for understanding self-assembl...Odd-numbered and high-nuclearity coordination clusters are extremely rare,yet they represent an intriguing subclass lacking regular repeating building blocks and high structural symmetry for understanding self-assembled multiatomic systems.Herein,the largest cobalt and polydentate ligand based cluster featuring odd-nuclearity,namely[Co_(19)(HL1)_(8)(L1)_(12)(L′)_(2)(Ac)_(4)]·10CH_(3)CH_(2)OH·6H_(2)O(1,H_(2)L1=1H-benzo[d]imidazole-2-yl)methanol,HL'=1H-benzo[d]imidazole),was obtained with in-situ ligand transformation from H_(2)L1 to L′.It features a hierarchical trilayer and void-cage inside structure,consisting of central disc-shaped[Co_(7)L_(10)]core with two[Co_(6)]rings on both sides.ESI-MS of crystal 1 yields a series of more than sixteen fragments,all featuring an integrated[Co_(19)]core,suggesting stability of the polynuclear cluster in solution.During increased in-source energy from 0 to 100 eV,all MS peaks shifted to a lower m/z range,but the[Co_(19)]core remained intact,excepting for the stepwise elimination of up to three Ac^(−)anions or three L1 linkers.PXRD tracking of the reaction sediments showed the formation of a key precursor of[Co_(4)L_(4)]cubane at 3 h,and its content decreased at 6 h and vanished at 12 h,followed by the appearance of crystals 1 by the generation of a clear solution at 18 h,suggesting an initial cluster assembly-disassembly process.ESI-MS spectra analysis of both reaction sediment and solution further identify the existence of other crucial higher-nuclearity reassembled fragments of[Co_(7)L_(10)]disk and its expansion of[Co_(13)L_(12)(L′)_(2)].A probable tandem assembly-disassembly-reassembly mechanism is put forward as[CoL_(2)]→[Co_(4)L_(4)]→[Co_(7)L_(10)]→[Co_(13)L_(12)(L′)_(2)]→[Co_(19)L_(2)0(L′)_(2)].Their evolution also indicated the ingenious synergy of coexisting organic,inorganic and in-situ generated ligands,along with diverse coordination geometries of metal ions,plays a directional role in forming odd-numbered and high-nuclearity coordination clusters.Magnetism analysis revealed antiferromagnetic coupling plays dominated role in the cluster.展开更多
Under the paradigm of Industry 5.0,intelligent manufacturing transcends mere efficiency enhancement by emphasizing human-machine collaboration,where human expertise plays a central role in assembly processes.Despite a...Under the paradigm of Industry 5.0,intelligent manufacturing transcends mere efficiency enhancement by emphasizing human-machine collaboration,where human expertise plays a central role in assembly processes.Despite advancements in intelligent and digital technologies,assembly process design still heavily relies on manual knowledge reuse,and inefficiencies and inconsistent quality in process documentation are caused.To address the aforementioned issues,this paper proposes a knowledge push method of complex product assembly process design based on distillation model-based dynamically enhanced graph and Bayesian network.First,an initial knowledge graph is constructed using a BERT-BiLSTM-CRF model trained with integrated human expertise and a fine-tuned large language model.Then,a confidence-based dynamic weighted fusion strategy is employed to achieve dynamic incremental construction of the knowledge graph with low resource consumption.Subsequently,a Bayesian network model is constructed based on the relationships between assembly components,assembly features,and operations.Bayesian network reasoning is used to push assembly process knowledge under different design requirements.Finally,the feasibility of the Bayesian network construction method and the effectiveness of Bayesian network reasoning are verified through a specific example,significantly improving the utilization of assembly process knowledge and the efficiency of assembly process design.展开更多
Elevation patterns and assembly processes of soil microbial community structures are essential for understanding biogeo-chemical processes in mountain systems.Differences in soil properties caused by elevation gradien...Elevation patterns and assembly processes of soil microbial community structures are essential for understanding biogeo-chemical processes in mountain systems.Differences in soil properties caused by elevation gradients can regulate the spatial distribu-tion and network complexity of the community structure.To explore the variations in soil microbial community structures and their as-sembly mechanisms across different elevations of the Changbai Mountains,as well as their responses to environmental factors,we col-lected microbial samples along an elevational gradient(seven elevations containing four vegetation zones)on the western slope of the Changbai Mountains using the method of metagenomic sequencing.The results showed a significant difference(P<0.05)for the Chao1 index across different elevations,but no significant difference was observed for the Shannon and Simpson indices.With increasing elev-ation,the number of nodes and links in the microbial network gradually decreased.Acidobacteria were highly connected to many nodes.The microbial communities indicated a significant distance-decay relationship(P<0.001)and were affected more by stochastic pro-cesses along the elevation gradient.The results of the Structural Equation Model(SEM)showed that elevation had direct significant ef-fect on carbon(C,P<0.01),nitrogen(N,P<0.01),and phosphorus(P,P<0.05)and weak negative effect on their ecological stoi-chiometry.Elevation was one of the major variables contributing to microbial network topology.The contribution of C and N to micro-bial network complexity was higher than that of P.Our study provides valuable insights into the responses of soil microbial communit-ies to elevation variations.展开更多
The assembly process of aerospace products such as satellites and rockets has the characteristics of single-or small-batch production,a long development period,high reliability,and frequent disturbances.How to predict...The assembly process of aerospace products such as satellites and rockets has the characteristics of single-or small-batch production,a long development period,high reliability,and frequent disturbances.How to predict and avoid quality abnormalities,quickly locate their causes,and improve product assembly quality and efficiency are urgent engineering issues.As the core technology to realize the integration of virtual and physical space,digital twin(DT)technology can make full use of the low cost,high efficiency,and predictable advantages of digital space to provide a feasible solution to such problems.Hence,a quality management method for the assembly process of aerospace products based on DT is proposed.Given that traditional quality control methods for the assembly process of aerospace products are mostly post-inspection,the Grey-Markov model and T-K control chart are used with a small sample of assembly quality data to predict the value of quality data and the status of an assembly system.The Apriori algorithm is applied to mine the strong association rules related to quality data anomalies and uncontrolled assembly systems so as to solve the issue that the causes of abnormal quality are complicated and difficult to trace.The implementation of the proposed approach is described,taking the collected centroid data of an aerospace product’s cabin,one of the key quality data in the assembly process of aerospace products,as an example.A DT-based quality management system for the assembly process of aerospace products is developed,which can effectively improve the efficiency of quality management for the assembly process of aerospace products and reduce quality abnormalities.展开更多
This paper reports the reengineering of the assembly processes of printed circuit boards (PCBs) used in computers.The new designed assembly processes are quite different from the traditional ones,and the business perf...This paper reports the reengineering of the assembly processes of printed circuit boards (PCBs) used in computers.The new designed assembly processes are quite different from the traditional ones,and the business performance is dramatically improved through establishing parallel workstations,off line workstation,merging workstations and organizing a small teamwork who cooperates in stations.“ITHINK”,a software package of business process reengineering (BPR),was used to analyze the current processes and create new processes.ITHINK is a powerful tool of BPR in modeling business processes,“soft” variables and conducting sensitivity analysis.The new assembly processes were tested over a period of 8 hours simulation.The results show that the new processes can increase throughput by 80% with only requiring less additional resources.The throughput can increase further by 17.5% when a small teamwork cooperates in some stations.展开更多
Assembly process planning(APP)for complicated products is a time-consuming and difficult work with conventional method.Virtual assembly process planning(VAPP)provides engineers a new and efficiency way.Previous studie...Assembly process planning(APP)for complicated products is a time-consuming and difficult work with conventional method.Virtual assembly process planning(VAPP)provides engineers a new and efficiency way.Previous studies in VAPP are almost isolated and dispersive,and have not established a whole understanding and discussed key realization techniques of VAPP from a systemic and integrated view.The integrated virtual assembly process planning(IVAPP)system is a new virtual reality based engineering application,which offers engineers an efficient,intuitive,immersive and integrated method for assembly process planning in a virtual environment.Based on analysis the information integration requirement of VAPP,the architecture of IVAPP is proposed.Through the integrated structure,IVAPP system can realize information integration and workflow controlling.In order to mode/the assembly process in IVAPP,a hierarchical assembly task list(HATL)is presented,in which different assembly tasks for assembling different components are organized into a hierarchical list.A process-oriented automatic geometrical constraint recognition algorithm(AGCR)is proposed,so that geometrical constraints between components can be automatically recognized during the process of interactive assembling.At the same time,a progressive hierarchical reasoning(PHR)model is discussed.AGCR and PHR will greatly reduce the interactive workload.A discrete control node model(DCNM)for cable harness assembly planning in IVAPP is detailed.DCNM converts a cable harness into continuous flexed line segments connected by a series of section center points,and designs can realize cable harness planning through controlling those control nodes.Mechanical assemblies(such as transmission case and engine of automobile)are used to illustrate the feasibility of the proposed method and algorithms.The application of IVAPP system reveals advantages over the traditional assembly process planning method in shortening the time-consumed in assembly planning and in minimizing the handling difficulty,excessive reorientation and dissimilarity of assembly operations.展开更多
There are heterogeneous problems between the CAD model and the assembly process document.In the planning stage of assembly process,these heterogeneous problems can decrease the efficiency of information interaction.Ba...There are heterogeneous problems between the CAD model and the assembly process document.In the planning stage of assembly process,these heterogeneous problems can decrease the efficiency of information interaction.Based on knowledge graph,this paper proposes an assembly information model(KGAM)to integrate geometric information from CAD model,non-geometric information and semantic information from assembly process document.KGAM describes the integrated assembly process information as a knowledge graph in the form of“entity-relationship-entity”and“entity-attribute-value”,which can improve the efficiency of information interaction.Taking the trial assembly stage of a certain type of aeroengine compressor rotor component as an example,KGAM is used to get its assembly process knowledge graph.The trial data show the query and update rate of assembly attribute information is improved by more than once.And the query and update rate of assembly semantic information is improved by more than twice.In conclusion,KGAM can solve the heterogeneous problems between the CAD model and the assembly process document and improve the information interaction efficiency.展开更多
The rotor initial unbalance of an aeroengine gas generator of turboshaft engine seriously affects rotor assembly process.To reasonably optimize rotor assembly process,the effect analyses of rotor initial unbalance of ...The rotor initial unbalance of an aeroengine gas generator of turboshaft engine seriously affects rotor assembly process.To reasonably optimize rotor assembly process,the effect analyses of rotor initial unbalance of single disc and combined discs on rotor dynamic characteristics are firstly implemented in respect of the dispersity of rotor initial unbalance.It is found that the most important factors contributing to rotor vibration are the unbalances of the first stage compressor disc and the second stage turbine disc.However,reducing the mass of two discs conflicts with the control of the whole gas generator rotor balance resulting from the unbalance increase of single components.Thus,we further analyze the key control factors of affecting rotor initial unbalance,and give the strict control measures of centrifugal impeller runout in the assembly process by adjusting the angle of central tie rod axis.The purpose of this measures to make the assembly process simpler and more effective for timely controlling rotor initial unbalance.The efforts of this study validate that the proposed method is workable for the rotor tightened by a central tie rod and possesses the significant meaning of practical application in engineering.展开更多
Computer-aided block assembly process planning based on rule-reasoning are developed in order to improve the assembly efficiency and implement the automated block assembly process planning generation in shipbuilding. ...Computer-aided block assembly process planning based on rule-reasoning are developed in order to improve the assembly efficiency and implement the automated block assembly process planning generation in shipbuilding. First, weighted directed liaison graph （WDLG） is proposed to represent the model of block assembly process according to the characteristics of assembly relation, and edge list （EL） is used to describe assembly sequences. Shapes and assembly attributes of block parts are analyzed to determine the assembly position and matched parts of parts used frequently. Then, a series of assembly rules are generalized, and assembly sequences for block are obtained by means of rule reasoning. Final, a prototype system of computer-aided block assembly process planning is built. The system has been tested on actual block, and the results were found to be quite efficiency. Meanwhile, the fundament for the automation of block assembly process generation and integration with other systems is established.展开更多
The layout and assembly of flexible cables play important roles in the design and development of complex electromechanical products.The rationality of cable layout design and the reliability of cable assembly greatly ...The layout and assembly of flexible cables play important roles in the design and development of complex electromechanical products.The rationality of cable layout design and the reliability of cable assembly greatly affect product quality.In this paper,we review the methods of cable layout design,cable assembly process planning,and cable assembly simulation.We first review research on flexible cable layout design(both interactive and automatic).Then,research on the cable assembly process planning,including cable assembly path and manipulation planning,is reviewed.Finally,cable assembly simulation is introduced,which includes general cable information,cable collision detection data,and cable assembly process modeling.Current problems and future research directions are summarized at the end of the paper.展开更多
Assembly process documents record the designers'intention or knowledge.However,common knowl-edge extraction methods are not well suitable for assembly process documents,because of its tabular form and unstructured...Assembly process documents record the designers'intention or knowledge.However,common knowl-edge extraction methods are not well suitable for assembly process documents,because of its tabular form and unstructured natural language texts.In this paper,an assembly semantic entity recognition and relation con-struction method oriented to assembly process documents is proposed.First,the assembly process sentences are extracted from the table through concerned region recognition and cell division,and they will be stored as a key-value object file.Then,the semantic entities in the sentence are identified through the sequence tagging model based on the specific attention mechanism for assembly operation type.The syntactic rules are designed for realizing automatic construction of relation between entities.Finally,by using the self-constructed corpus,it is proved that the sequence tagging model in the proposed method performs better than the mainstream named entity recognition model when handling assembly process design language.The effectiveness of the proposed method is also analyzed through the simulation experiment in the small-scale real scene,compared with manual method.The results show that the proposed method can help designers accumulate knowledge automatically and efficiently.展开更多
Job planning (JP) systems shop oriented provide a basis for job shop scheduling and control in organizing short term production activities. This paper presents a method based on timed Petri net (TPN) method that is ...Job planning (JP) systems shop oriented provide a basis for job shop scheduling and control in organizing short term production activities. This paper presents a method based on timed Petri net (TPN) method that is used to program optimal JP for assembly shop. It includes three parts further. Firstly, an architecture of solutions to JP problems for any kind of shop oriented is presented to define a particular JP for a designated JP problem. Secondly, Petri net model is specified for aircraft part assembly processes. Finally, algorithms for optimizing generation of dynamic mechanism and a simulating case are then discussed. In comparison with traditional methods such as PERT or CPM, it is obviously convenient for planners or schedulers to schedule and manage assembly processes.展开更多
To analyze the physical structure of assembly process and assure product quality, the quality stability of multi-station assembly process was investigated. First, the assembly process was modeled as a one-dimensional ...To analyze the physical structure of assembly process and assure product quality, the quality stability of multi-station assembly process was investigated. First, the assembly process was modeled as a one-dimensional discrete variant system by state space equation based on variation stream. Then, the criterion to judge whether the process is stable or not and the index, stability degree, to show the level of stability were proposed by analyzing the bounded-input bounded-output (BIBO) stability of system. Finally, a simulated example of a sheet metal assembly process with three stations, was provided to verify the effectiveness of the proposed method.展开更多
In times of digitalisation, visual assistance systems in assembly are increasingly important. The design of these assembly systems needs to be highly complex to meet the requirements. Due to the increasing number of v...In times of digitalisation, visual assistance systems in assembly are increasingly important. The design of these assembly systems needs to be highly complex to meet the requirements. Due to the increasing number of variants in production processes, as well as shorter innovation and product life cycles, assistance systems should improve quality and reduce complexity of assembly processes. However, many large kitchen manufacturers still assemble kitchen cabinets manually, due to the high variety of components, such as rails and fittings. This paper focuses on the analysis and evaluation of virtual assistance systems to improve quality and usability in individualised kitchen cabinet assembly processes at a large German manufacturer. A solution is identified and detailed.展开更多
Based on the problems of complex assembly process route, low resource utilization, low assembly efficiency and low quality in the production process of assembly workshop, a knowledge-based intelligent assembly worksho...Based on the problems of complex assembly process route, low resource utilization, low assembly efficiency and low quality in the production process of assembly workshop, a knowledge-based intelligent assembly workshop management and control mode is proposed. By constructing an intelligent assembly workshop with real assembly workshop, knowledge assembly workshop and assembly workshop management and control system working together, On the basis of realizing real-time information collection of resource location information, assembly process information and assembly quality information, Euclidean distance algorithm, Markov method and Manhattan distance algorithm are used to realize resource optimization scheduling, assembly process and quality control.展开更多
In the safety management of machinery and equipment in mining enterprises, mining enterprises should create a safe and reliable production environment for their staff, so as to ensure their life safety. From the angle...In the safety management of machinery and equipment in mining enterprises, mining enterprises should create a safe and reliable production environment for their staff, so as to ensure their life safety. From the angle of 5M1E, systematically sort out and identify all kinds of change points in the assembly process of mining machinery products, output the list of change points and formulate corresponding control measures to standardize them. When the change points are opened, what measures should be taken within the specified time, and how to track the effective implementation of the measures, so as to ensure the smooth progress of production and the effective control of assembly quality.展开更多
基金Supported by the National Natural Science Foundation of China(Nos.42141003,42176147)the National Key Research and Development Program of China(No.2022YFF0802204)the Xiamen Key Laboratory of Urban Sea Ecological Conservation and Restoration(USER)(Nos.USER2021-1,USER2021-5)。
文摘Ecological floating bed is an important biological remediation method for water pollution control.During the removal of excess nutrients and pollutants,changes in environmental factors affect the characteristics of microorganisms in aquatic ecosystems.To understand the influences of ecological floating beds on size-fractionated microorganisms,we investigated the community assembly and nitrogen metabolic characteristics of three size-fractionated microorganism groups in the ecological floating bed area,using 18S rDNA,16S rDNA metabarcoding,and metagenomic sequencing techniques.Firstly,we discovered substantial differences between size-fractionated groups in the diversity and compositions of both microeukaryotic and bacterial communities,as well as the influences of floating beds on specific groups.The floating beds appeared to provide more habitats for heterotrophs and symbiotes while potentially inhibiting the growth of certain phytoplankton(cyanobacteria).Secondly,we observed that microeukaryotic and bacterial communities were predominantly influenced by stochastic and deterministic processes,respectively,and they both exhibited distinct patterns across different size-fractionated groups.Notably,microeukaryotic community assembly demonstrated a greater sensitivity to ecological floating beds,as indicated by an increase in dispersal limitation processes.Finally,the nitrogen metabolism functional genes revealed that microbes associated with large-sized particles played a crucial role in dissimilatory nitrate reduction to ammonium(DNRA)and denitrification processes within the floating bed area,thereby facilitating the removal of excess nitrogen nutrients from the water.In contrast,freeliving microorganisms from small-sized groups were linked mainly to the genes involved in nitrogen assimilation and assimilatory nitrate reduction to ammonium(ANRA)processes.These findings help understand the impact of ecological floating beds on the diversity and functional characteristics of microorganism communities in different size-fractionated groups.
基金supported by the Natural Resources Science and Technology Innovation Project of Fujian Province,China(No.KY-090000-04-2022-012)the National Natural Science Foundation of China(Nos.42077041 and 42377301)+1 种基金the National Natural Science Foundation of Fujian Province,China(No.2021J011038)the Talent Introduction Program of Minjiang University,China(No.MJY20012).
文摘Soil microbiomes are significant for biodiversity,crucial for ecosystem functions,and vital for the health of various organisms.Nevertheless,the impacts of season and plant species shifts on soil microbial diversity and community assembly are still poorly understood.This study explored soil bacterial,fungal,and protistan communities during summer and winter in a coastal wetland affected by Spartina alterniflora invasion and subsequent Cyperus malaccensis or Kandelia obovata restoration.The results showed that bacterial,fungal,and protistan diversity were 2.63%,40.3%,and 9.90%higher in winter than in summer,respectively.Plant species had a distinct impact on microbial diversity.Notably,K.obovata restoration significantly increased bacterial diversity,but decreased protistan diversity,with no effect on fungal diversity when compared to S.alterniflora invasion.Season and plant species both significantly influenced the community structure of bacteria,fungi,and protists.However,protistan community structure was more sensitive to season compared to the structure of bacterial and fungal communities.The complexity of co-occurrence networks within or among bacteria,fungi,and protists was higher in winter than in summer.Bacterial and protistan community assembly was primarily driven by stochastic processes,while fungal assembly was dominated by deterministic processes.Bacterial and protistan community assembly exhibited lower stochasticity in winter compared to summer,suggesting a more deterministic assembly of communities during winter.Our findings highlight the critical role of season and plant species in regulating microbial communities,revealing higher microbial diversity,network complexity,and determinism in community assembly during winter compared to summer in a subtropical coastal wetland.
基金supported by the National Key Research and Development Program of China(No.2022YFD 1901601)the National Natural Science Foundation of China(No.42107360)the Fundamental Research Funds for the Central Universities,China(No.2452021032).
文摘phoD and pqqC gene occurrence in bacteria allows them to mobilize phosphorus(P)by mineralizing organic P(Po)and solubilizing inorganic P(Pi),respectively.Community characteristics of phoD-and pqqC-harboring bacteria(phoD-and pqqC-HB,respectively)mediate P cycling.However,whether the microbial community assembly and keystone taxa of phoD-and pqqC-HB regulate P availability and distinct regulatory pathways between these two genes remain unclear.In this study,soil microbial community characteristics and P availability were investigated in four long-term(38-year)fertilization regimes:control with no fertilizer(CK),P fertilizer(PF),nitrogen(N)and P fertilizers(NP),and N fertilizer,P fertilizer,and manure(NPM).The N addition treatments(NP and NPM)significantly changed the community composition and increased the abundances of phoD-and pqqC-HB compared to the no-N addition treatments(CK and PF).Stochastic processes dominated the community assembly of both phoD-and pqqC-HB,and the relative contributions of stochasticity increased with N addition.Furthermore,the N addition treatments resulted in greater network complexity and higher abundances of keystone taxa of phoD-and pqqC-HB compared to those of the no-N addition treatments.The keystone taxa implicated in P cycling were also associated with carbon(C)and N cycling processes.Microbial community composition and assembly processes were the main factors driving labile Pi for phoD-HB,whereas keystone taxa contributed the most to labile Pi for pqqC-HB.These results emphasize that distinct mechanisms of phoD-and pqqC-HB regulate P availability under fertilization management and underline the significance of microbial community assembly and keystone taxa in soil ecological functions,offering fresh perspectives on comprehending the biological processes facilitated by microorganisms in enhancing soil quality.
基金supported by grants from the National Natural Science Foundation of China for Excellent Young Scientists Fund Program(No.42222105)the National Natural Science Foundation of China General Program(No.42171144)+1 种基金the Assessment of Ecosystem Carbon Stock and Turnover Patterns in Qinghai Province(No.2021-SFA7-1-1)the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2021QZKK0100)。
文摘Bacterial communities play a crucial role in permafrost biogeochemical cycling and ecosystem function maintenance.Bacterial interaction is one of the main factors in shaping soil bacterial communities.However,how would bacterial interaction influence the bacterial communities in permafrost of the Qinghai-Tibet Plateau(QTP)remains largely unknown.Here we collected paired soil samples from both the active and permafrost layers of two typical QTP permafrost regions in October 2020 for Tuotuohe River(TTH)and May 2022 for Aerjin(ARJ),and investigated the bacterial communities and the role of interactions in structuring the bacterial community and its assembly process through amplicon sequencing of the 16S rRNA gene.Our study revealed distinct bacterial communities,with significant differences in the relative abundances of Proteobacteria(P<0.05),Acidobacteriota(P<0.001),Bacteroidota(P<0.05),and Planctomycetota(P<0.001)between the active layer and the permafrost layer.More importantly,we found that interspecies interactions,including both positive and negative associations,were strongly correlated with bacterial alpha-diversity and played a significant role in community variation and assembly process.Our findings also showed that the community assembly in both the active and permafrost layers was primarily driven by homogeneous selection of deterministic processes,with interspecies interactions accounting for more than 58%and 63%of all assembly mechanisms,respectively.This is the first study to quantify the contribution of bacterial interactions in shaping the bacterial community and its assembly process in permafrost of QTP,highlighting the importance of considering interspecies interactions in future modeling efforts.Our work also emphasizes the necessity of including interspecies interactions in microbial process projections to reduce uncertainty.
基金supported by the BAGUI Talent Program in Guangxi Province(No.2019AC26001)the National Natural Science Foundation of China(Nos.22171075,U23A2080,22371173).
文摘Odd-numbered and high-nuclearity coordination clusters are extremely rare,yet they represent an intriguing subclass lacking regular repeating building blocks and high structural symmetry for understanding self-assembled multiatomic systems.Herein,the largest cobalt and polydentate ligand based cluster featuring odd-nuclearity,namely[Co_(19)(HL1)_(8)(L1)_(12)(L′)_(2)(Ac)_(4)]·10CH_(3)CH_(2)OH·6H_(2)O(1,H_(2)L1=1H-benzo[d]imidazole-2-yl)methanol,HL'=1H-benzo[d]imidazole),was obtained with in-situ ligand transformation from H_(2)L1 to L′.It features a hierarchical trilayer and void-cage inside structure,consisting of central disc-shaped[Co_(7)L_(10)]core with two[Co_(6)]rings on both sides.ESI-MS of crystal 1 yields a series of more than sixteen fragments,all featuring an integrated[Co_(19)]core,suggesting stability of the polynuclear cluster in solution.During increased in-source energy from 0 to 100 eV,all MS peaks shifted to a lower m/z range,but the[Co_(19)]core remained intact,excepting for the stepwise elimination of up to three Ac^(−)anions or three L1 linkers.PXRD tracking of the reaction sediments showed the formation of a key precursor of[Co_(4)L_(4)]cubane at 3 h,and its content decreased at 6 h and vanished at 12 h,followed by the appearance of crystals 1 by the generation of a clear solution at 18 h,suggesting an initial cluster assembly-disassembly process.ESI-MS spectra analysis of both reaction sediment and solution further identify the existence of other crucial higher-nuclearity reassembled fragments of[Co_(7)L_(10)]disk and its expansion of[Co_(13)L_(12)(L′)_(2)].A probable tandem assembly-disassembly-reassembly mechanism is put forward as[CoL_(2)]→[Co_(4)L_(4)]→[Co_(7)L_(10)]→[Co_(13)L_(12)(L′)_(2)]→[Co_(19)L_(2)0(L′)_(2)].Their evolution also indicated the ingenious synergy of coexisting organic,inorganic and in-situ generated ligands,along with diverse coordination geometries of metal ions,plays a directional role in forming odd-numbered and high-nuclearity coordination clusters.Magnetism analysis revealed antiferromagnetic coupling plays dominated role in the cluster.
基金Supported by National Key Research and Development Program(Grant No.2024YFB3312700)National Natural Science Foundation of China(Grant No.52405541)the Changzhou Municipal Sci&Tech Program(Grant No.CJ20241131)。
文摘Under the paradigm of Industry 5.0,intelligent manufacturing transcends mere efficiency enhancement by emphasizing human-machine collaboration,where human expertise plays a central role in assembly processes.Despite advancements in intelligent and digital technologies,assembly process design still heavily relies on manual knowledge reuse,and inefficiencies and inconsistent quality in process documentation are caused.To address the aforementioned issues,this paper proposes a knowledge push method of complex product assembly process design based on distillation model-based dynamically enhanced graph and Bayesian network.First,an initial knowledge graph is constructed using a BERT-BiLSTM-CRF model trained with integrated human expertise and a fine-tuned large language model.Then,a confidence-based dynamic weighted fusion strategy is employed to achieve dynamic incremental construction of the knowledge graph with low resource consumption.Subsequently,a Bayesian network model is constructed based on the relationships between assembly components,assembly features,and operations.Bayesian network reasoning is used to push assembly process knowledge under different design requirements.Finally,the feasibility of the Bayesian network construction method and the effectiveness of Bayesian network reasoning are verified through a specific example,significantly improving the utilization of assembly process knowledge and the efficiency of assembly process design.
基金Under the auspices of the National Natural Science Foundation of China(No.42430511,U20A2083)the National Key Research and Development Program of China(No.2022YFF1300900)the Science and Technology Development Program of Jilin Province(No.20210509037RQ,20230101348JC)。
文摘Elevation patterns and assembly processes of soil microbial community structures are essential for understanding biogeo-chemical processes in mountain systems.Differences in soil properties caused by elevation gradients can regulate the spatial distribu-tion and network complexity of the community structure.To explore the variations in soil microbial community structures and their as-sembly mechanisms across different elevations of the Changbai Mountains,as well as their responses to environmental factors,we col-lected microbial samples along an elevational gradient(seven elevations containing four vegetation zones)on the western slope of the Changbai Mountains using the method of metagenomic sequencing.The results showed a significant difference(P<0.05)for the Chao1 index across different elevations,but no significant difference was observed for the Shannon and Simpson indices.With increasing elev-ation,the number of nodes and links in the microbial network gradually decreased.Acidobacteria were highly connected to many nodes.The microbial communities indicated a significant distance-decay relationship(P<0.001)and were affected more by stochastic pro-cesses along the elevation gradient.The results of the Structural Equation Model(SEM)showed that elevation had direct significant ef-fect on carbon(C,P<0.01),nitrogen(N,P<0.01),and phosphorus(P,P<0.05)and weak negative effect on their ecological stoi-chiometry.Elevation was one of the major variables contributing to microbial network topology.The contribution of C and N to micro-bial network complexity was higher than that of P.Our study provides valuable insights into the responses of soil microbial communit-ies to elevation variations.
基金National Key Research and Development Program of China(Grant No.2020YFB1710300)National Natural Science Foundation of China(Grant No.52005042)+2 种基金National Defense Fundamental Research Foundation of China(Grant No.JCKY2020203B039)Equipment Pre-research Foundation of China(Grant No.80923010101)Beijing Institute of Technology Research Fund Program for Young Scholars.
文摘The assembly process of aerospace products such as satellites and rockets has the characteristics of single-or small-batch production,a long development period,high reliability,and frequent disturbances.How to predict and avoid quality abnormalities,quickly locate their causes,and improve product assembly quality and efficiency are urgent engineering issues.As the core technology to realize the integration of virtual and physical space,digital twin(DT)technology can make full use of the low cost,high efficiency,and predictable advantages of digital space to provide a feasible solution to such problems.Hence,a quality management method for the assembly process of aerospace products based on DT is proposed.Given that traditional quality control methods for the assembly process of aerospace products are mostly post-inspection,the Grey-Markov model and T-K control chart are used with a small sample of assembly quality data to predict the value of quality data and the status of an assembly system.The Apriori algorithm is applied to mine the strong association rules related to quality data anomalies and uncontrolled assembly systems so as to solve the issue that the causes of abnormal quality are complicated and difficult to trace.The implementation of the proposed approach is described,taking the collected centroid data of an aerospace product’s cabin,one of the key quality data in the assembly process of aerospace products,as an example.A DT-based quality management system for the assembly process of aerospace products is developed,which can effectively improve the efficiency of quality management for the assembly process of aerospace products and reduce quality abnormalities.
基金Supported by NSFC (No.79770 0 63) and Natural Sciences and En-gineering Research Council of Canada
文摘This paper reports the reengineering of the assembly processes of printed circuit boards (PCBs) used in computers.The new designed assembly processes are quite different from the traditional ones,and the business performance is dramatically improved through establishing parallel workstations,off line workstation,merging workstations and organizing a small teamwork who cooperates in stations.“ITHINK”,a software package of business process reengineering (BPR),was used to analyze the current processes and create new processes.ITHINK is a powerful tool of BPR in modeling business processes,“soft” variables and conducting sensitivity analysis.The new assembly processes were tested over a period of 8 hours simulation.The results show that the new processes can increase throughput by 80% with only requiring less additional resources.The throughput can increase further by 17.5% when a small teamwork cooperates in some stations.
基金supported by National Natural Science Foundation of China(Grant No.50805009)The Eleventh Five Year Plan Defense Pre-Research Fund,China(Grant No.51318010205)
文摘Assembly process planning(APP)for complicated products is a time-consuming and difficult work with conventional method.Virtual assembly process planning(VAPP)provides engineers a new and efficiency way.Previous studies in VAPP are almost isolated and dispersive,and have not established a whole understanding and discussed key realization techniques of VAPP from a systemic and integrated view.The integrated virtual assembly process planning(IVAPP)system is a new virtual reality based engineering application,which offers engineers an efficient,intuitive,immersive and integrated method for assembly process planning in a virtual environment.Based on analysis the information integration requirement of VAPP,the architecture of IVAPP is proposed.Through the integrated structure,IVAPP system can realize information integration and workflow controlling.In order to mode/the assembly process in IVAPP,a hierarchical assembly task list(HATL)is presented,in which different assembly tasks for assembling different components are organized into a hierarchical list.A process-oriented automatic geometrical constraint recognition algorithm(AGCR)is proposed,so that geometrical constraints between components can be automatically recognized during the process of interactive assembling.At the same time,a progressive hierarchical reasoning(PHR)model is discussed.AGCR and PHR will greatly reduce the interactive workload.A discrete control node model(DCNM)for cable harness assembly planning in IVAPP is detailed.DCNM converts a cable harness into continuous flexed line segments connected by a series of section center points,and designs can realize cable harness planning through controlling those control nodes.Mechanical assemblies(such as transmission case and engine of automobile)are used to illustrate the feasibility of the proposed method and algorithms.The application of IVAPP system reveals advantages over the traditional assembly process planning method in shortening the time-consumed in assembly planning and in minimizing the handling difficulty,excessive reorientation and dissimilarity of assembly operations.
基金the National Natural Science Foundation of China(No.51805079)。
文摘There are heterogeneous problems between the CAD model and the assembly process document.In the planning stage of assembly process,these heterogeneous problems can decrease the efficiency of information interaction.Based on knowledge graph,this paper proposes an assembly information model(KGAM)to integrate geometric information from CAD model,non-geometric information and semantic information from assembly process document.KGAM describes the integrated assembly process information as a knowledge graph in the form of“entity-relationship-entity”and“entity-attribute-value”,which can improve the efficiency of information interaction.Taking the trial assembly stage of a certain type of aeroengine compressor rotor component as an example,KGAM is used to get its assembly process knowledge graph.The trial data show the query and update rate of assembly attribute information is improved by more than once.And the query and update rate of assembly semantic information is improved by more than twice.In conclusion,KGAM can solve the heterogeneous problems between the CAD model and the assembly process document and improve the information interaction efficiency.
文摘The rotor initial unbalance of an aeroengine gas generator of turboshaft engine seriously affects rotor assembly process.To reasonably optimize rotor assembly process,the effect analyses of rotor initial unbalance of single disc and combined discs on rotor dynamic characteristics are firstly implemented in respect of the dispersity of rotor initial unbalance.It is found that the most important factors contributing to rotor vibration are the unbalances of the first stage compressor disc and the second stage turbine disc.However,reducing the mass of two discs conflicts with the control of the whole gas generator rotor balance resulting from the unbalance increase of single components.Thus,we further analyze the key control factors of affecting rotor initial unbalance,and give the strict control measures of centrifugal impeller runout in the assembly process by adjusting the angle of central tie rod axis.The purpose of this measures to make the assembly process simpler and more effective for timely controlling rotor initial unbalance.The efforts of this study validate that the proposed method is workable for the rotor tightened by a central tie rod and possesses the significant meaning of practical application in engineering.
基金National Natural Science Foundation of China (No.40606018)
文摘Computer-aided block assembly process planning based on rule-reasoning are developed in order to improve the assembly efficiency and implement the automated block assembly process planning generation in shipbuilding. First, weighted directed liaison graph （WDLG） is proposed to represent the model of block assembly process according to the characteristics of assembly relation, and edge list （EL） is used to describe assembly sequences. Shapes and assembly attributes of block parts are analyzed to determine the assembly position and matched parts of parts used frequently. Then, a series of assembly rules are generalized, and assembly sequences for block are obtained by means of rule reasoning. Final, a prototype system of computer-aided block assembly process planning is built. The system has been tested on actual block, and the results were found to be quite efficiency. Meanwhile, the fundament for the automation of block assembly process generation and integration with other systems is established.
基金the National Defense Fundamental Research Foundation of China(JCKY2017204B502,JCKY2016204A502)and National Natural Science Foundation of China(51935003).
文摘The layout and assembly of flexible cables play important roles in the design and development of complex electromechanical products.The rationality of cable layout design and the reliability of cable assembly greatly affect product quality.In this paper,we review the methods of cable layout design,cable assembly process planning,and cable assembly simulation.We first review research on flexible cable layout design(both interactive and automatic).Then,research on the cable assembly process planning,including cable assembly path and manipulation planning,is reviewed.Finally,cable assembly simulation is introduced,which includes general cable information,cable collision detection data,and cable assembly process modeling.Current problems and future research directions are summarized at the end of the paper.
文摘Assembly process documents record the designers'intention or knowledge.However,common knowl-edge extraction methods are not well suitable for assembly process documents,because of its tabular form and unstructured natural language texts.In this paper,an assembly semantic entity recognition and relation con-struction method oriented to assembly process documents is proposed.First,the assembly process sentences are extracted from the table through concerned region recognition and cell division,and they will be stored as a key-value object file.Then,the semantic entities in the sentence are identified through the sequence tagging model based on the specific attention mechanism for assembly operation type.The syntactic rules are designed for realizing automatic construction of relation between entities.Finally,by using the self-constructed corpus,it is proved that the sequence tagging model in the proposed method performs better than the mainstream named entity recognition model when handling assembly process design language.The effectiveness of the proposed method is also analyzed through the simulation experiment in the small-scale real scene,compared with manual method.The results show that the proposed method can help designers accumulate knowledge automatically and efficiently.
文摘Job planning (JP) systems shop oriented provide a basis for job shop scheduling and control in organizing short term production activities. This paper presents a method based on timed Petri net (TPN) method that is used to program optimal JP for assembly shop. It includes three parts further. Firstly, an architecture of solutions to JP problems for any kind of shop oriented is presented to define a particular JP for a designated JP problem. Secondly, Petri net model is specified for aircraft part assembly processes. Finally, algorithms for optimizing generation of dynamic mechanism and a simulating case are then discussed. In comparison with traditional methods such as PERT or CPM, it is obviously convenient for planners or schedulers to schedule and manage assembly processes.
基金Supported bythe National High-Tech Research and Development Plan (National"863"Plan) (No2006AA04Z115)Tianjin Science andTechnology Key Project (No05YFGDGX08700)
文摘To analyze the physical structure of assembly process and assure product quality, the quality stability of multi-station assembly process was investigated. First, the assembly process was modeled as a one-dimensional discrete variant system by state space equation based on variation stream. Then, the criterion to judge whether the process is stable or not and the index, stability degree, to show the level of stability were proposed by analyzing the bounded-input bounded-output (BIBO) stability of system. Finally, a simulated example of a sheet metal assembly process with three stations, was provided to verify the effectiveness of the proposed method.
文摘In times of digitalisation, visual assistance systems in assembly are increasingly important. The design of these assembly systems needs to be highly complex to meet the requirements. Due to the increasing number of variants in production processes, as well as shorter innovation and product life cycles, assistance systems should improve quality and reduce complexity of assembly processes. However, many large kitchen manufacturers still assemble kitchen cabinets manually, due to the high variety of components, such as rails and fittings. This paper focuses on the analysis and evaluation of virtual assistance systems to improve quality and usability in individualised kitchen cabinet assembly processes at a large German manufacturer. A solution is identified and detailed.
文摘Based on the problems of complex assembly process route, low resource utilization, low assembly efficiency and low quality in the production process of assembly workshop, a knowledge-based intelligent assembly workshop management and control mode is proposed. By constructing an intelligent assembly workshop with real assembly workshop, knowledge assembly workshop and assembly workshop management and control system working together, On the basis of realizing real-time information collection of resource location information, assembly process information and assembly quality information, Euclidean distance algorithm, Markov method and Manhattan distance algorithm are used to realize resource optimization scheduling, assembly process and quality control.
文摘In the safety management of machinery and equipment in mining enterprises, mining enterprises should create a safe and reliable production environment for their staff, so as to ensure their life safety. From the angle of 5M1E, systematically sort out and identify all kinds of change points in the assembly process of mining machinery products, output the list of change points and formulate corresponding control measures to standardize them. When the change points are opened, what measures should be taken within the specified time, and how to track the effective implementation of the measures, so as to ensure the smooth progress of production and the effective control of assembly quality.
