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The X bill of material (XBOM) of a missile and rocket product is a comprehensive and basic support document produced by a multi-stakeholder that considers structural composition, data information and interactional processes in different life stages. The XBOM data management of missile and rocket products coordinates the data organization and control in the whole life cycle, eliminates the interactional disconnection and one-way transmission between related parties, business and data in different life stages and provides effective data source support for the full digital model supply. To meet the requirements of organic integration and multi-party collaboration, this paper proposes the XBOM data management method based on digital thread. Firstly, the digital thread framework is analyzed, and the XBOM data management architecture based on the digital thread is proposed and established. Secondly, guided by the hierarchy of "data-interaction-modeling-application", the XBOM data management method for the missile and rocket product are developed, including data organization, data relational analysis, data modeling and data application. Finally, the structural system of a certain model of carrier rocket is studied, and the XBOM data management system based on digital thread is developed and its application is validated.

Due to the significant differences in aerodynamic loads offlaps at different positions, there are also significant differences in the loads borne by bearings at different flap angles. This leads to inconsistent wear depth of bearings at different angles. Therefore, the method of introducing uniform wear depth is difficult to apply to the dynamic characteristics analysis of flaps. To address this issue, a dynamic modeling method based on the least squares method is proposed. Firstly, based on the connection characteristics of the flap surface, the C-B method is used to make it flexible, and the RBE2 element is used to establish a rigid flexible coupling dynamic model. On this basis, combining with UAMP, DISP and UMESHMOTION subroutines, the uneven wear data of hinge bearings are obtained by using the wear evolution simulation. At the same time, the function relation among the wear depth, flap deflection angle, and friction coefficient is established via least squares fitting. Finally, the function relation is updated to the rigid-flexible coupling dynamic model by the offset of the hinge bearing center point and the friction coefficient of the ball pair, so as to obtain the dynamic response of the flap under the influence of wear, which verifies the applicability and effectiveness of the method. As wear progresses, the coaxiality of the inner and outer bearing shafts of the flaps decreases gradually, and the driving torque on the inner and outer sides increases accordingly. The maximum increase is 15.08%. This method can provide some support for designing the flap mechanism and bearing selection.

Least risk bomb location(LRBL) structure is a device for placing suspicious explosives on the aircraft.Exploring the influence of structure size and explosive location on its anti-explosion performance can provide a reference for improving the design. Based on the method of combining orthogonal experimental design with numerical simulation, the maximum strain and deformation of each dangerous part of LRBL structure are used as evaluation indicators. The range analysis method and variance analysis method are respectively used to carry out parameter sensitivity analysis on the five influencing factors of the tank wall thickness, bottom cover thickness, connection boss thickness, shear pin diameter and explosive position of LRBL structure. The results show that when the explosive equivalent is determined as 200 g, the significant degree of influence of each factor on the antiknock performance of the LRBL structure from large to small is as follows: explosive position, tank wall thickness, bottom cover thickness, boss thickness and shear pin diameter; Based on comprehensive analysis of evaluation indicators, the LRBL structural design scheme at the optimal level of each factor is obtained.

With the refinement of civil aircraft technology and the enhancement of product complexity, civil aircraft design has changed from traditional text-based system engineering to model-based system engineering, the expression of the system has also transformed from text-centered to model-centered. To further improve the model quality and correctness of aircraft system modeling, this paper explores the applicability of model-driven and verification-oriented system engineering methods in the field of civil aircraft design, and establishes the system engineering practice framework of civil aircraft design, which can ensure the rapid design and efficient delivery of civil aircraft. Firstly, starting from the Harmony SE modeling method, the workflow and modeling ideas of system are introduced; then the noticeable problems in the practice of civil aircraft system engineering are analyzed, and the system engineering practice of civil aircraft design is established with the support of the applicability of the Harmony SE method; finally, the fuel tank pressurization component is taken as the research object of the practice system in component-level. The results show that the system engineering practice framework of civil aircraft design and method proposed in this paper can correctly and reasonably allocate design requirements and establish a complete system model, which is helpful to improve the efficiency and accuracy of civil aircraft design at this stage.

The deflecting to airflow flap of civil aircraft are generally driven by complex multi-hinge mechanisms in space. According to the requirements of the airworthiness clause CCAR25.671, it is necessary to carry out research on the mechanism characteristics under typical faults. Firstly, a digital prototype of the mechanism motion is constructed, and the hinge point of the rigid multi-hinge mechanism is associated with the flexible flap body by using the RBE2 unit, and the rigid-flexible coupling dynamic model of the flap mechanism is established. Then, under three aerodynamic load conditions of cruise, take-off and landing, two typical faults, hinge jamming and one-side failure of control system, are simulated by adjusting the hinge friction coefficient and setting one-side driving failure. Finally, the variation law of driving torque and hinge point load is analyzed. The results show that:when the hinge is stuck, the inner drive link ear piece is stretched and damaged; when the inner drive fails, the radial load at the hinge point of the outer rocker arm increases significantly. In practice, we should focus on the middle joint of the outer rocker arm of this type of flap. The radial and axial load-bearing capacity of the bearing avoids the situation of separate manipulation of the outer mechanism, and at the same time, it is necessary to increase the torque protection for the entire drive system.

To effectively monitor the reliability of civil aircraft flap deflection angle, combined with the quick access recorder(QAR), the collaborative intelligent moving Kriging(CIMK) method is proposed by absorbing the Kriging model, decomposition and co-ordination strategy, equilibrium optimizer(EO), and moving least square(MLS). Among them, the decomposition coordination strategy is used to deal with the relationship between the flaps left and right deflection angles. MLS is employed to select effective modeling samples and solve the undetermined coefficients of Kriging model. EO method is applied to determine optimizing the local compact support region radius of MLS. Firstly, the fault reason for flap left-right asymmetry is analyzed to clarify the main characteristic parameters in QAR data. Secondly, combined with the QAR data of relevant influencing parameters, the civil aircraft flap deflection model(limit state function) is constructed by using CIMK. Then, the reliability and influence of civil aircraft flap deflection angle are analyzed by Monte Carlo(MC) sampling method. The results show that when the flap deflection angle is 3°, the reliability is 0.450 2, and the important factors affecting the flap deflection angle are Mach number, left angle of attack, right angle of attack, etc. Compared with the response surface method(RSM), Kriging, support vector machine(SVM), and back-propagation-artificial neural network(BP-ANN), the average absolute error accuracy of the proposed method is relative improved by 53.02%, 51.43%, 49.03%, and 44.04%, the average relative error accuracy is relative improved by 68.36%, 66.76%, 64.41%, and 62.64%, and the modeling efficiency is relative improved by 50.62%, 26.35%, and 43.01% respectively compared with Kriging, SVM and BP-ANN. When the number of simulations is 103, the analysis accuracy is relative improved by 8.82%, 7.25%, 6.22%, and 3.98% respectively.

To effectively monitor the operation state of landing gear, a back propagation neural network-based on multi-strategy cooperative optimization(MSCO-BPNN) is proposed. The multi-strategy optimization algorithm is composed of chaotic mapping strategy, adaptive spiral capture strategy, crossover mutation strategy and whale optimization algorithm(WOA). WOA is applied to find the optimal hyperparameters of back propagation neural network(BPNN). The search efficiency, multi-local search ability and global search performance of model can be improved by using chaotic mapping strategy, adaptive spiral capture strategy and crossover mutation strategy. The BPNN with optimal hyperparameters is introduced to establish the implicit model of input parameters and output responses. Based on quick access recorder(QAR) data, landing gear left side brake temperature is act as the monitoring objective of this paper. The validity and applicability of MSCO-BPNN are verified by compared with WOA-BPNN, particle swarm optimization BPNN and traditional BPNN. The results show that MSCO-BPNN can monitor the operation status of landing gear with high efficiency and accuracy. The efforts of this paper provide a promising insight for the precise condition monitoring of complex structures.

Temperature is one of the important characteristic parameters of civil aircraft hydraulic system performance. To effectively realize the temperature monitoring of hydraulic system, the method of Kriging model based on atomic search (ASOKM) is proposed based on Kriging model and atomic search optimization (ASO) algorithm. Firstly, the temperature fault causes of hydraulic system are analyzed, and the fault logic diagram is established to clarify the characteristic parameters affecting the hydraulic system temperature. Then, combined with the quick access recorder (QAR) data, the modeling principle of ASOKM method is introduced. Finally, the effectiveness of the proposed ASOKM method is verified by the temperature monitoring analysis of domestic civil aircraft hydraulic systems. The results show that, in comparison with response surface method (RSM), Kriging, and back-propagation-artificial neural network (BP-ANN) models, the training and monitoring average absolute errors of the ASOKM method are lower, which is of higher accuracy, efficiency and robustness. The proposed ASOKM method can provide a reference for reliability analysis, fault diagnosis, and predictive maintenance of the hydraulic system.

In response to the issue of reducing satellite constellation backup costs while meeting constellation availability target,it is the hot issue in current research.In this paper,the impact of different spare strategies on the performance of a low earth orbit(LEO)satellite constellation are studied and the best spare strategy that takes into account both the performance and economic efficiency of the constellation is selected.First and foremost,a constellation availability model with degraded operation is developed.Secondly,the Markov process is used to solve this model.Last but not least,the availability of the constellation with different spare strategies at different constellation levels is calculated based on the operation data of a real LEO satellite constellation.The results show that deploying two backup satellites in each orbit can make the constellation with the lowest spare cost while meeting the availability target.The spare strategy proposed in this paper has a certain reference value for the construction of LEO satellite constellations and can provide guidance for the accurate configuration of spare satellites with reasonable cost reduction.

To study the typical fault diagnosis and fault location technology of the hydraulic system of the domestic civil aircraft, the logic data of the typical fault is constructed according to the formation conditions of the fault. The operation data of the typical fault is collected, and the Bayesian network is used to realize the fault diagnosis and fault components position. First, according to the fault formation conditions in the unit operation manual of a certain type of domestic civil aircraft, referring to the construction method of the logic data, taking the typical fault of the hydraulic system as an example, the fault logic data of the domestic civil aircraft is established to intuitively reflect the logical relationship of the fault formation; secondly, based on the constructed logic data, considering the formation conditions of the fault, a Bayesian network corresponding to the logic data is established, and the logical relationship formed by the fault is represented by the value of the conditional probability distribution; obtain quick access recorder (QAR) data and its parameter information according to the input information of the logic data; finally, according to the established Bayesian network and the obtained QAR data, apply forward reasoning to realize the diagnosis of typical faults of the hydraulic system. Under the condition of partial information, reverse reasoning is applied to locate the faulty components of hydraulic system. The research shows that the proposed method can accurately diagnose faults, and can accurately locate faulty components in complete information, and give the probability of occurrence of potentially faulty components under partial information, which can effectively assist in the location of faulty components. The research work has certain reference significance for improving the fault diagnosis function of the airborne health management system and the ground health management system of domestic civil aircraft.

Aiming at the combined action effect of the corrosive environment of amphibious aircraft wading structures and random loads including water surface take-off and landing impact, based on the standard load spectrum TWIST of transport aircraft, considering the load level and frequency corresponding to the hydrodynamic load, the simulated random load spectrum of the wading structure was first compiled; the Willenborg/Chang high-load hysteresis model was used to consider the hysteretic effect of hydrodynamic high-amplitude overload on structural crack propagation, and an engineering method for damage tolerance analysis of amphibious aircraft wading structures was established. Taking the common hole edge crack of a typical wading structure of a certain type of aircraft as an example, based on the Franc3D crack propagation analysis software, the crack propagation life under the combined action of corrosive environment and random load spectrum was analyzed, and the inspection threshold value and check interval for maintaining the airworthiness of the structure were determined by residual strength analysis. The method proposed in this study is simple and feasible, and provides a theoretical basis for the damage tolerance analysis and maintenance plan formulation of amphibious aircraft wading structures.

Aging is an important risk factor for tumorigenesis. Metabolic reprogramming is a hallmark of both aging and tumor initiation. However, the manner in which the crosstalk between aging and metabolic reprogramming affects the tumor microenvironment (TME) to promote tumorigenesis was poorly explored. We utilized a computational approach proposed by our previous work, MMP3C (Modeling Metabolic Plasticity by Pathway Pairwise Comparison), to characterize aging-related metabolic plasticity events using pan-cancer bulk RNA-seq data. Our analysis revealed a high degree of metabolically organized heterogeneity across 17 aging-related cancer types. In particular, a higher degree of several energy generation pathways, i.e., glycolysis and impaired oxidative phosphorylation, was observed in older patients. Similar phenomena were also found via single-cell RNA-seq analysis. Furthermore, those energy generation pathways were found to be weakened in activated T cells and macrophages, whereas they increased in exhausted T cells, immunosuppressive macrophages, and Tregs in older patients. It was suggested that aging-induced metabolic switches alter glucose utilization, thereby influencing immune function and resulting in the remodeling of the TME. This work offers new insights into the associations between tumor metabolism and the TME mediated by aging, linking with novel strategies for cancer therapy. [ABSTRACT FROM AUTHOR]

The drooping front leading edge is a simple lifting device,which can effectively reduce the aerodynamic noise and the motion space of the mechanism. It has been applied to A380 and A350XW. In order to realize the fixing rotation of drooping leading according to given requirement,it is necessary to design a drooping front mechanism type,so a design method of hinged drooping front mechanism based on four-link is proposed in this paper. According to the design input requirements,the wire frame model of the droop leading edge mechanism is established,and the kinematics and rigid-flexible coupling dynamics simulation of the mechanism are carried out. The angle variation parameters,and driving moment and the hinge point load in the mechanism are obtained. The results show that,with the uniform rotation of the driving arm,the hinged droop front can be steadily reduced by 26°,the ratio of the maximum driving torque of the two driving planes is close to 3∶2,and the lateral load at the driving position is improved by the setting of the side strut. The design of the mechanism is reasonable,and provides a good reference for the design of modern civil aircraft.

The situation of civil aircraft structure repair process may beyond the scope of the manual,a civil aircraft structure repair plan platform based on Browser/Service(B/S)is developed in this paper,which is aim to provide the relevant reference scheme of maintenance engineers in the formulation process of structure repair process beyond the scope of the manual. Firstly,the platform requirements are analyzed from the perspective of business process and platform function. Secondly,on the basis of technologies used in the platform development,the platform design is analyzed in detail from three aspects of platform architecture,database and platform function module. Finally,the main function modules of the platform are tested through the actual operation demonstration. The results show that the platform has friendly man-machine interface,good expansibility,simple and convenient operation,can realize the electronization of civil aircraft structure damage information and repair scheme,and automatically recommend several repair schemes stored in the database according to the damage information,which provides support for the maintenance engineering department to quickly formulate the repair scheme beyond the manual.

In order to improve the comprehensive logistics support capability of domestic and foreign civil aircraft markets, and reduce the number of air materiel configuration and the cost of air materiel operation support, this paper proposes an air materiel configuration method based on air materiel sharing mode, considering the air materiel inventory and response time of each terminal. The Poisson process is used to describe the probabilities of different demand quantities of aviation materials during the study time; the aviation materials sharing group is constructed according to the transportation time relationship between the terminals; the marginal analysis method is used to expect largest number short-term aviation materials of all terminals in the sharing group to carry out air material configuration until the fleet availability needs are met, and the air material configuration technology under the sharing of air materials is realized. Studies have shown that under the specified fleet availability, the use of air material configuration technology under the condition of air material sharing can reduce the number of air materials in each terminal; the availability of the fleet can be improved under the same configuration number; The initial inventory can be maintained at a low level in the terminal group under the sharing condition. the research work has certain reference significance for improving the maintenance and support system of Chinese civil aircraft.

It is very important for the economic operation of civil aircraft to make reasonable procurement and configuration of aviation materials between multiterminals.The theoretical algorithm content formed by the research of aviation material prediction and configuration is relatively complex.In order to promote the effective application of these algorithm programs,based on the Java language,and the algorithm programs written in Matlab and Python are integrated,a multi language hybrid programming system platform for the prediction and configuration of civil aircraft is developed.Firstly,the support vector machine algorithm and marginal analysis algorithm integrated in the system platform are introdused,and the implementation of hybrid programming is described.Then,the details of the system platform design are expounded,and the implementation of hybrid programming and the conversion method of different types of programming language’s parameter are explained.Finally,the system platform functions are tested with the actual engineering data.The result shows that the platform’s human-machine interface is friendly and easy to operate,and it can better realize the functions of aviation material prediction and aviation material configuration,which can provide reference and ideas for the relevant theoretical algorithm to meet the engineering needs through platform technology.

As the key part of maintenance support,the accuracy support of aviation material plays an important role in the inventory management cost reduction,fund allocation optimization and flight safety improvement.In order to support the normal take-off of aircraft,improve the operating income of airline companies and reduce the cost of aviation material support,a material consumption forecast model based on support vector machine regression is proposed to overcome the problem which is difficult to forecast aviation material consumption with small sample size and large variation.Taking the actual consumption data of a domestic civil aircraft as an example,the forecast accuracy of the support vector machine regression model is verified.The results show that the support vector machine regression model is of good adaptability for small sample data,and has higher forecast accuracy than that of the exponential smoothing method.

Hinge mechanism as a widely used motion mechanism in civil aircraft,the reasonable formulation of its maintenance interval plays an important role in ensuring the safe and economic operation of aircraft.By analyzing the MSG-3,China Civil Aviation Administration and Military Standard of China,and the influencing factors of maintenance interval,the formulation process of the maintenance interval of the hinge mechanism of civil aircraft is proposed.The maintenance interval formulation of flap hinge mechanism of an aircraft is taken as an example to verify the process.The results show that the proposed process in this paper is feasible,which can provide the basis for the reasonable formulation of maintenance interval and maintenance program of aircraft hinge mechanism.The inspection threshold and repeated inspection interval of accidental damage and environmental damage of the hinge mechanism are 5 calendar years,the inspection threshold of fatigue damage is 24 000 fh and the repeated inspection interval is 14 400 fh.

Level of repair analysis(LORA)is an important part of maintenance engineering analysis for amphibious aircraft wading structure.There are many studies mainly focusing on LORA of civil aircraft,shipboard aircraft,vehicles,ships and so on in the domestic and overseas,while studies on LORA of amphibious aircraft wading structure are few.Based on this,the process and method of LORA for the wading structure of amphibious aircraft are studied in this paper.A three-level repair model of the wading structure is established,and the LORA process of the wading structure is proposed.An economical LORA(ELORA)model for three-level repair of wading structure is established,and the cost factors to be considered for ELORA are given.The approach switch on the wading cabin door of an amphibious aircraft is taken as an example to carry out ELORA.The results show that the approach switch should be repaired in intermediate-level depot,which is in accordance with reality,and the ELORA model used on wading structure is feasible.

it is an important link to verify and determine the candidate items of the preliminary master minimum equipment list(PMMEL)for the main civil aircraft manufacturer passing through airworthiness certification.In this paper a new PMMEL fuzzy comprehensive evaluation method of civil aircraft is proposed.Firstly,the factors domain of fuzzy comprehensive evaluation is established by analyzing the purpose of PMMEL.Then,the different fuzzy weights by using the analytic hierarchy process are determined and a fuzzy comprehensive evaluation model of PMMEL is set up.The fuzzy comprehensive evaluation results are obtained.Finally,a PMMEL candidate project of the civil aircraft main landing gear down lock spring is taken as an example.Result shows that the new PMMEL evaluation method combined with the expert-based evaluation and essential fuzzy analysis is feasible and accurate,which can accurately get the clear result of whether the candidate project is allowed to be included in PMMEL and provide the analysis result verification for the traditional PMMEL method.It has important value and bright prospects for application.

Preventive maintenance is an indispensable part of civil aircraft operational support activities,and it is also the basis for ensuring the safe and economic operation of civil aircraft.As the first international general standard for preventive maintenance,S4000P provides preventive maintenance with a reasonable analysis method for the for-mulation of initial maintenance tasks throughout the life cycle,the analysis of unplanned maintenance tasks,and the optimization of initial maintenance tasks through operating data.In this paper the research status of preventive maintenance is combed,the S4000P standard is analyzed,and the analysis framework of civil aircraft preventive maintenance is established based on S4000P,which provides strong support for promoting the formulation and optimization process of civil aircraft preventive maintenance.

Reliability evaluation during aero-engine operation is one of the key issues in the field of reliability evaluation of aero-engine,and the reasonable evaluation method can improve the reliability analysis efficiency and accuracy,therefore a method to support the evaluation of aeroengine operation reliability in the process of aircraft mission is proposed in this paper.Based on the characteristics of flight mission and aeroengine,the quick access recorder(QAR)information is used as the analysis data to analyze the operational reliability,and the operation reliability is analyzed by considering the current operating environment,the transient state of the aircraft,and the current working state of the engine.The random forest algorithm is combined with stratified sampling method to fit,predict and calculate the feature importance.B737-800 flight mission from Beijing to Urumqi is taken as an example to verify the effectiveness and feasibility of the method.The results show that the proposed reliability evaluation method can solve the problem of data processing difficulty caused by large amount of data and high dimension in the process of aeroengine operation.

Aiming at the lack of unified evaluation index for the sensitivity analysis of fault tree of the system, the Analytic Hierarchy Process(AHP) is introduced into Fault Tree Analysis(FTA), and an FTA-AHP method is proposed to generate the comprehensive sensitivity evaluation index of the system. Firstly, the reliability analysis model of the system fault tree is established, and three indexes including probabilistic sensitivity, relative sensitivity and structural sensitivity, are calculated by using the traditional sensitivity analysis method. Then, combined with the analytic hierarchy process, the weight coefficients were determined according to the sensitivity analysis results above and the type of the minimum cut set, and the comprehensive sensitivity evaluation and analysis of the system fault tree were carried out. Finally, the case verification shows that compared with the traditional method, the comprehensive sensitivity ranking results have less repeatability, and the factors are considered comprehensively, which is convenient for decision makers to make judgment. The synthetic sensitivity evaluation model developed provides support for system reliability analysis.

Operational consequence analysis of system failure is an important branch of aircraft operational reliability analysis, which can provide strong support for cost-benefit analysis of maintenance tasks.In order to study the impact of aircraft system failure on operational consequences and costs, this study starts with the correlation analysis of operational consequences of system failures.Firstly, the impact of aircraft system fault types and release conditions on operational consequences is analyzed.Then, combined with the current practice of airline maintenance and the idea of event tree, a method to support the evaluation of operational consequences and related costs of aircraft system failures is proposed, and the operational consequence and cost assessment model based on aircraft system failure is established.Finally, the feasibility and applicability of the proposed method are verified by taking the fuel system of a certain type of aircraft as an example.The results show that the proposed method is reasonable and effective, which can provide support for evaluating the consequences of failure operation, and provide certain reference for aircraft design, operation and maintenance.

Reasonable line replaceable unit (LRU) division can effectively improve the maintenance efficiency of civil aircraft, avoid the phenomenon of aircraft parking, and ensure the safe and reliable operation of civil aircraft. Under the premise of considering the influence of various factors in the design stage and operation process of civil aircraft, the design and operation of civil aircraft are carried out, a method of LRU division, two-step iterative analytical hierarchy process (TSI-AHP), is proposed. Firstly, the influence of relevant factors in the design and operation stages on LRU division of civil aircraft is investigated. Secondly, the influence of various factors are comprehensive considered, and the lowest structures of product decomposed by their function are regarded as the study objects, and the TSI-AHP is applied to implement LRU division of civil aircraft. Finally, the landing gear system of ARJ21-700 aircraft is treated as an example to realize the LRU division using the method proposed. The results show that the LRU partition method based on TSI-AHP can effectively realize the LRU partition of landing gear system of ARJ21-700 aircraft. The LRU partition project in this paper is basically consistent with the actual LRU project, which verifies the feasibility and effectiveness of this method, and provides a new idea for the LRU partition of domestic civil aircraft.

As the material base of integrated logistic support (ILS), scientific prediction and reasonable configuration of spare parts can effectively ensure the safe and economic operation of civil aircraft. To achieve all-win results for stakeholders (manufacturers, operators, repairers, etc.), this paper conducts an investigation on the prediction and configuration management technologies for civil aircraft spare parts, and discusses its development trend in future. Firstly, the research status for the prediction technologies of civil aircraft spare parts is introduced. Secondly, the research status for the configuration management methods is explored of civil aircraft spare parts. Finally, the development trend of civil aircraft spare parts prediction and configuration management technology is studied based on the advantages and disadvantages of the existing methods. The aim of this paper is to provide a reference for the comprehensive management of domestic civil aircraft spare parts, and to improve the maintenance support system of civil aircraft.

The essence of crashworthiness is to study the protection of people（ crew and passengers）,and the head injury of the occupants accounted for a large proportion in the crash. In order to investigate the influences of different impact velocity on the occupant ’s head injury under horizontal impact conditions,a comprehensive evaluation method based on occupant ’s Abbreviated Injury Scale（ AIS） and occupant’s injury risk probability to evaluate occupant injury is proposed,and a dynamic simulation model which including seat,restraint system and dummy was constructed by LS-Dyna software. Take the typical civil aircraft double-tube triple-seat as research objects,the effects of different horizontal impact velocity（ 8. 0 m/s,10. 0 m/s,12. 0 m/s,14. 0 m/s,16. 0 m/s） on the head injury of occupants,the stages and characteristics of injuries were analyzed. The results of dummies‘ dynamic response analysis shows that occupants may be severely injured in the head and legs during the aircraft’s longitudinal impact,occupant’head injury increases rapidly with the increase of horizontal impact velocity,and occupant’fatality rate increases exponentially with increasing horizontal impact velocity,the substantial leg movement of the occupants greatly increase the risk of injuries caused by collisions with other facilities in the cabin. In addition,the dummies ’ head trajectory,the peak load of seat belt is proportional to the horizontal impact velocity. Therefore,when the crash occurs,the horizontal impact velocity should be controlled deliberately（ the fatality rate was less than 10% when the impact velocity was13. 0 m/s,and more than 80% when the impact velocity was 16. 0 m/s）.

The ultimate goal of aircraft crashworthiness design is to protecting safety for occupants. In order to more accurately simulate the dynamic response and injury of the occupants during crash event,a crash simulation model of the fuselage section which including dummy and seat restraint system was developed using LS-Dyna,and the dynamic response of the structure and occupants is analyzed in detail when the vertical impact velocity is 9. 14 m/s,the analysis includes the energy absorption characteristics and failure mode of the fuselage structure,the mooring condition of the cabin facilities,the movement and injury of the occupants,etc.,and the validity of the crash simulation model is verified by comparison simulation results with the test data.Finally,the research on the evaluation method of civil aircraft crashworthiness was carried out. Through understanding and identification of relevant airworthiness clauses,advisory circular and standards,the comprehensively evaluation method to evaluating the crashworthiness of civil aircraft was proposed based on the survival space,the strength of mooring,the injury of occupants,the evacuation channel and the post-crash environment. The crashworthiness analysis of the fuselage section shows that the injury modes of occupant in the vertical crash environment are mainly lumbar and tibia injuries,the occupant’s maximum compression lumbar load is 6. 78 k N,and the maximum axial tibia load is 7. 46 k N during the crash process. The crashworthiness of the constructed civil aircraft is systematically evaluated by the comprehensive crashworthiness evaluation method proposed in this paper,it shows that the crashworthiness of this civil aircraft is good,except for the occupant’s lumbar load slightly exceeding the airworthiness limit and requiring corresponding design improvements,the other evaluation indexes are all in accordance with the requirements.

Do U.S. households with battery electric vehicles (BEVs) drive less or more than U.S. households with internal combustion engine vehicles (ICEVs)? Answering this question is important to policymakers and transportation planners concerned with reducing vehicle miles traveled and the emissions of greenhouse gases from transportation. So far, this question has not been answered satisfactorily, possibly because of the relatively low number of EVs in the U.S. until recently, but also because of methodological issues. In this paper, we aim to fill this gap by analyzing data from the 2017 National Household Travel Survey (NHTS). We apply propensity score matching (PSM), a quasi-experimental method, to examine the differences in self-reported annual mileage and calculated daily mileage for various trip purposes among households with only BEVs (BEV-only), households with both BEVs and ICEVs (BEV+), and households without BEVs (non-BEV households). Our findings indicate that households with BEVs drive fewer annual miles than non-BEV households, but typically travel no less than they do for daily activities. This apparent discrepancy is likely due to taking fewer longer trips because the public charging infrastructure was still in its infancy in 2017, and its reliability was questionable. As technological progress is helping to overcome current battery limitations, policymakers may consider measures for fostering fast charging technologies while pondering new measures to fund both the charging infrastructure and the road network. [ABSTRACT FROM AUTHOR]

Operational reliability is the basis of ensuring the safe and economic operation of civil aircraft, S5000F(international code for in service data and feedback) provides an opportunity for the systematic study of reliability analysis and feedback and life cycle management of civil aircraft. This paper interprets the S5000F specification. Firstly, the background and purpose of S5000F are described. Then, the main content of S5000F specification and related business process are introduced. Finally, the application of S5000F specification in reliability analysis and feedback of civil aircraft operation is discussed. Based on S5000F specification, the business process of civil aircraft operation data collection is sorted out, and a data-based operation reliability analysis framework is formed, which provides effective guidance for life cycle management.

In order to solve the problems of many factors affecting spare parts consumption forecast, complex time correlation, and few actual consumption samples, in view of the difficulty of capturing the gradual dependence of small sample spare parts consumption data in time sequence with existing methods, a spare parts consumption prediction method based on the improved generation adversarial network generative model and the recurrent neural network prediction model is proposed. This method combines the supervised training of autoregressive learning with the unsupervised training of adversarial learning, and further explores the potential static distribution and temporal step-by-step dependence distribution of the spare parts consumption data. Samples that are closer to the real data are generated to achieve the purpose of expanding the sample volume and improving the forecast accuracy of spare parts consumption. Taking the consumption data of a certain type of domestic civil aircraft as an example, the generation performance and forecast accuracy of the model are evaluated by using the dimensionality reduction visualization method and the forecast score. Compared with other methods, the average absolute error of the predicted value presented by the proposed method is reduced by 3%, which verifies the effectiveness of the proposed method in solving the problem of spare parts prediction. [ABSTRACT FROM AUTHOR]

Depending on the form of mechanism,the hinge wear and rod end bearing wear are considered respectively,and the self-lubricating rod end bearing wear model are established.Then the over-center locking reliability analysis model of four bar linkage mechanism is built under the "effective lever length theory"and "continuous contact model"hypothesis,besides,a reliability analysis method of over-center locking considering the initial clearance and wear is presented.The results show that the failure probability of mechanism over-center locking will rapidly increase after a certain number of cycles; the reliability of mechanism over-center locking will be significantly improved by using self-lubricating rod end spherical plain bearing.

Using composite laminates with a bolt-filled hole were proposed to study interlaminar stress distribution of laminates joints hole-edge,and a 3D finite element model with a zero-thickness cohesive element was established for solving holeedge interlaminar stress of laminated plate in tension.The results show that interlaminar normal stress distribution along the hole mainly affected by the bolt-clamping force,under the same bolt-clamping force,interlaminar normal stress value ranges is close;The interlaminar shear stress impact both by the bolt-clamping force and interface ply parameters,such as interlaminar shear stress of [-45 /90] and [0 /-45] interface is larger than others; Interlaminar normal stress caused by bolt-clamping force was mainly compressive stress,and it is beneficial for the interlaminar strength,but interlaminar shear stress generated in the same time is not help to improve the interlaminar strength,therefore,a reasonable clamping force can enhance the interlaminar strength for bolt composite joints.