Oil and gas production systems have the characteristics of high operation and maintenance risk and great accident influence.With the deep integration of informationization and industrialization,the development directio...Oil and gas production systems have the characteristics of high operation and maintenance risk and great accident influence.With the deep integration of informationization and industrialization,the development direction and necessary choice of the oil and gas industry is to develop the oil and gas production system into the interconnected,multi-domain interactive cyber-physical intelligent system.In order to avoid or reduce the complex,diverse and potentially unknown safety risks in the process of oil and gas production,improve the safety and reliability of oil and gas production system and increase the production efficiency,this paper analyzes the safety problems occurring in the intelligentization process of oil and gas production system and constructs a system from the perspective of operation and maintenance based on key elements of intelligent safe operation and maintenance technology,combined with the typical production scenarios in the oil and gas production industry.And the following research results are obtained.First,the connotation of intelligent safe operation and maintenance technology is clarified,the key elements and existing problems and challenges of intelligent safe operation and maintenance technology are analyzed,and the“1-2-3-4-5-6”intelligent safe operation and maintenance technology system of oil and gas production system is constructed,which empowers six key technologies with key elements of oil and gas production to realize the essential safety of oil and gas production system.Second,the intelligent safe operation and maintenance technology actively promotes the application and implementation of condition monitoring,health management,risk assessment,intelligent early warning technologies in typical production scenarios such as drilling and extraction,storage and transportation,refining and chemical industry in up,middle and down streams of oil and gas production.Third,in view of the characteristics of oil and gas production system under digital transformation,it is proposed to develop the intelligent safe operation and maintenance technology with the functions of intelligent decision-making,active prevention and comprehensive safety in the future to help the safe construction in thefield of oil and gas production and promote the safe and healthy development of the oil and gas industry.In conclusion,the research on intelligent safe operation and maintenance technology system of oil and gas production system is conducive to the safe construction in thefield of oil and gas production,which will not only provide technical support for the realization of trouble-free oil and gas production system,but also provide reference for the intelligent development of the world oil and gas industry.展开更多
Transmission and distribution line is an important part of the grid system, therefore, in the grid planning and design, transmission and distribution line occupies a very important position, in order to ensure the nor...Transmission and distribution line is an important part of the grid system, therefore, in the grid planning and design, transmission and distribution line occupies a very important position, in order to ensure the normal and safe operation of the power system grid, need to focus on the planning and design of the grid system of transmission and distribution line safe operation. This paper mainly introduces the current situation of transmission and distribution lines in the power system planning and design and the countermeasures to realize its safe operation, which is of great significance to promote the power system planning and design in China.展开更多
On May 1st, China National Nuclear Corporation(CNNC) announced in Beijing that unit 1 and unit 2 ofTianwan Nuclear Power Plant cooperatively constructedby China and Russia have completed in succession thefirst fuel cy...On May 1st, China National Nuclear Corporation(CNNC) announced in Beijing that unit 1 and unit 2 ofTianwan Nuclear Power Plant cooperatively constructedby China and Russia have completed in succession thefirst fuel cycle operation continuously and safely. It is展开更多
As an important basic tool for power transmission, most of the overhead transmission lines are exposed to the natural environment, the design and construction methods are different. And there are many man-made damage ...As an important basic tool for power transmission, most of the overhead transmission lines are exposed to the natural environment, the design and construction methods are different. And there are many man-made damage factors during operation, which reduce the normal operation capacity of the transmission line, and cause the fault that the line can not transmit electric energy, The safety status of the overhead transmission line itself is not only related to the overall development of the power industry, but also has an important impact on the power users. Therefore, it is quite necessary to identify, analyze and evaluate the risks in the operation system of the transmission line, which can provide the basis for the adjustment of equipment, operation management, operation and maintenance, so as to eliminate and control the risk factors existing in the transmission line system and minimize the occurrence of accidents. So as to achieve the best safe operation state.展开更多
Sixteen inverted siphons are in operation at the Beijing-Shijiazhuang section in the Middle Route of the South-to-North Water Diversion Project. Their safe operation is closely related to the safety and the water dive...Sixteen inverted siphons are in operation at the Beijing-Shijiazhuang section in the Middle Route of the South-to-North Water Diversion Project. Their safe operation is closely related to the safety and the water diversion efficiency of the whole project during an ice period. The ice accumulation process at the inlet of the inverted siphon is modeled under a real ice condition, and then the hydraulic conditions of the ice jam prevention are confirmed. According to the experimental results and the design sizes of the inverted siphons, the detailed safe water diversion discharge and the operational water level are studied. Analysis results of these inverted siphons provide references for the safe operation and the reasonable regulations during the ice period.展开更多
In this paper,the least square support vector machine(LSSVM)is used to study the safety of a high-speed railway.According to the principle of LSSVM regression prediction,the parameters of the LSSVM are optimized to mo...In this paper,the least square support vector machine(LSSVM)is used to study the safety of a high-speed railway.According to the principle of LSSVM regression prediction,the parameters of the LSSVM are optimized to model the natural disaster early warning of safe operation of a high-speed railway,and the management measures and methods of high-speed railway safety operation under natural disasters are given.The relevant statistical data of China’s high-speed railway are used for training and verification.The experimental results show that the LSSVM can well reflect the nonlinear relationship between the accident rate and the influencing factors,with high simulation accuracy and strong generalization ability,and can effectively predict the natural disasters in the safe operation of a high-speed railway.Moreover,the early warning system can improve the ability of safety operation evaluation and early warning of high-speed railway under natural disasters,realize the development goals of high-speed railway(safety,speed,economic,low-carbon and environmental protection)and provide a theoretical basis and technical support for improving the safety of a high-speed railway.展开更多
The navigation enterprise has no fixed business, no stable customers, even no stable operation team, poor technical strength, poor profitability, poor economic strength, nonstandard management, etc., and there are gre...The navigation enterprise has no fixed business, no stable customers, even no stable operation team, poor technical strength, poor profitability, poor economic strength, nonstandard management, etc., and there are great risks in safe flight operation. For small-scale navigation enterprises, it is very important to ensure the safe and stable operation of aircraft, which is a core asset. How to ensure the safe and healthy operation of the maintenance system of small-scale navigation enterprises by means of management is the main research direction of this paper. Based on the idea of project management, this paper explores the safe and healthy operation of the maintenance system in small-scale navigation enterprises.展开更多
Electric power, as one of the basic elements of social operation, promotes the economic development of various places, and the importance of power plants is self-evident. Whether the power plant can work efficiently a...Electric power, as one of the basic elements of social operation, promotes the economic development of various places, and the importance of power plants is self-evident. Whether the power plant can work efficiently and maintain the quality of output will affect the stability of power. So the safety of power plant must be paid attention to. In safety management, we should pay special attention to the emergency problems. We should prepare the corresponding countermeasures to solve the unexpected accidents and minimize the losses. This kind of safety management is complete enough to ensure the safe operation of the power plant.展开更多
Urban gas projects play an important role in the development of urbanization in China. The safe construction and management of urban gas production and operation have great influence on the safe use and quality of urb...Urban gas projects play an important role in the development of urbanization in China. The safe construction and management of urban gas production and operation have great influence on the safe use and quality of urban gas. In the process of urbanization, the continuous construction and development of gas engineering not only greatly promotes the development of society, but also greatly facilitates people's daily production and life. However, it also has some security risks. Therefore, it is necessary to give high priority to urban gas engineering construction and safe production operation management, comprehensively utilize daily operation management, institutional safety and high-tech capabilities, and effectively improve the safety of urban gas production operation.展开更多
Safe and just operating spaces(SJOS)are influenced by complex cross-scale interactions and cascading effects spanning global,regional,and local landscape scales.However,existing SJOS research has often focused on sing...Safe and just operating spaces(SJOS)are influenced by complex cross-scale interactions and cascading effects spanning global,regional,and local landscape scales.However,existing SJOS research has often focused on single-scale assessments,overlooking the impacts of multiscale interactions and within-region heterogeneity on urban SJOS.To address this gap,we developed a cross-scale framework for assessing urban SJOS,explicitly incorporating top-down influences from upper-level constraints and bottom-up effects from lower-level heterogeneity.This approach was applied to China's five major metropolises to examine the states and cross-scale dynamics influencing urban SJOS between 1990 and 2020.Our findings reveal that the SJOS of China's metropolises were primarily influenced by factors at national and local landscape scales,with weaker influences from the global and continental scales.A persistent trade-off between social justice and environmental safety was identified across spatiotemporal scales.For instance,Chongqing in southwestern China lagged behind the eastern four metropolises in social performance but exhibited stronger environmental safety due to its extensive natural landscapes,which mitigated the anthropogenic impacts of urban centers.Regional issues,such as the overshoot of PM_(2.5)and ecological footprints(EF),were primarily driven by the bottom-up accumulation of localized pressures,while the overshoot of CO_(2)was attributed to national policy constraints and the universal exceedance of safe thresholds across scales.Addressing urban sustainability requires avoiding adverse cascading effects from other levels by emphasizing landscape heterogeneity within metropolises and fostering coordinated collaboration across scales,particularly at the regional landscape and national levels.展开更多
[Objective]This study aims to investigate the multi-body hydrodynamic interaction mechanisms during offshore lifting operations of aquaculture net cages in wind-fishery integration systems.By integrating numerical sim...[Objective]This study aims to investigate the multi-body hydrodynamic interaction mechanisms during offshore lifting operations of aquaculture net cages in wind-fishery integration systems.By integrating numerical simulations and dynamic analysis methods,this study systematically investigates the coupled dynamic response characteristics during the cage-carrier vessel separation process to reveal its dynamic evolution patterns and key influence mechanisms.[Method]Based on potential flow theory,a fully coupled dynamic analysis model of crane vessel-net cage-semi-submersible barge was established for a marine ranch project in Guangdong.The complete lifting process was dynamically simulated using SESAM software.Five typical operating sea states were configured to investigate the influence of wave parameters on the system's motion response under combined wave-current-wind actions.[Result]The results demonstrate that wave period dominates the system stability.Under short-period conditions,the system maintains stable motion with relatively small horizontal relative displacements,while long-period conditions excite low-frequency resonance,leading to significant slow-drift motions.Vertical response analysis reveals that long-period waves cause severe relative displacement fluctuations between the cage and semi-submersible vessel,with actual displacement amplitudes doubling the preset safety target of 2.045 m.Quantitative analysis further indicates that when significant wave height increases from 1.0 m to 1.5 m,the actual displacement amplitude increases by approximately 20%relative to the target displacement of 2.045 m,demonstrating that its influence is significantly weaker than the displacement variations induced by wave period changes.The complete dynamic simulation successfully captures the continuous dynamic response characteristics during the lifting process.[Conclusion]This research clarifies the influence mechanisms of wave parameters on the cage lifting process,identifying wave period as the crucial factor for operational safety.An operation window assessment method incorporating multi-body coupling effects is established,proposing a safety criterion with peak period not exceeding six seconds as the core requirement.The findings provide theoretical foundation for safe installation of marine ranch net cages and offer valuable references for similar offshore lifting operations.展开更多
In order to explore the safe operation of UAVs in non-segregated airspace,a collision risk model for cylindrical UAVs based on conflict areas was constructed and the risk of conflict between manned and unmanned aerial...In order to explore the safe operation of UAVs in non-segregated airspace,a collision risk model for cylindrical UAVs based on conflict areas was constructed and the risk of conflict between manned and unmanned aerial vehicles was researched.According to the results of risk analysis,a strategy for solving the conflict of aircraft is proposed,and the risk assessment experiment of unmanned aerial vehicle(UAV)in non-isolated airspace conflict is carried out.The results show that under the experimental conditions,large unmanned aerial vehicles equipped with ADS-B,TCAS and other airborne sensing systems will indeed interfere with other aircraft in airspace when they enter non-isolated airspace.Especially when the number of aircraft in airspace is large,the automatic avoidance system of UAV will increase the avoidance time and trigger the safety alarm,but the safety level is still acceptable.This indicates that it is relatively safe for UAVs to enter non-isolated airspace under limited conditions.The results can be used as a reference for the safe operation of unmanned aerial vehicle(UAV)in non-isolated airspace.展开更多
With the over-exploitation of traditional energy sources such as coal and oil and the advent of the world energy crisis, new energy sources such as wind and solar energy have attracted more and more attention from the...With the over-exploitation of traditional energy sources such as coal and oil and the advent of the world energy crisis, new energy sources such as wind and solar energy have attracted more and more attention from the world. New energy can not only alleviate the energy crisis, but also can be more environmentally friendly than traditional energy, and it can be recycled for a long time. Wind energy is an important form of wind energy utilization. It is one of the renewable energy projects with the most mature technology, the largest scale of development, and the broadest prospects for commercial development. Wind energy is a pollution-free, renewable and mature technology, so it is very popular. At present, there are hidden dangers in the operation management and technical quality of wind farms, which affect the safe operation of wind turbines. This paper studied the safe operation and control technology of direct drive wind turbines, analyzed the operation that affects safety, and provided a solution to solve this problem. The safe operation of the equipment during the entire life cycle ensures its rapid development.展开更多
A novel silicon carbide(SiC) trench metal–oxide–semiconductor field-effect transistor(MOSFET) with a dual shield gate(DSG) and optimized junction field-effect transistor(JFET) layer(ODSG-TMOS) is proposed. The combi...A novel silicon carbide(SiC) trench metal–oxide–semiconductor field-effect transistor(MOSFET) with a dual shield gate(DSG) and optimized junction field-effect transistor(JFET) layer(ODSG-TMOS) is proposed. The combination of the DSG and optimized JFET layer not only significantly improves the device’s dynamic performance but also greatly enhances the safe operating area(SOA). Numerical analysis is carried out with Silvaco TCAD to study the performance of the proposed structure. Simulation results show that comparing with the conventional asymmetric trench MOSFET(Con-ATMOS), the specific on-resistance(Ron,sp) is significantly reduced at almost the same avalanche breakdown voltage(BVav). Moreover, the DSG structure brings about much smaller reverse transfer capacitance(Crss) and input capacitance(Ciss), which helps to reduce the gate–drain charge(Qgd) and gate charge(Qg). Therefore, the high frequency figure of merit(HFFOM) of Ron,sp·Qgdand Ron,sp· Qgfor the proposed ODSG-TMOS are improved by 83.5% and 76.4%, respectively.The switching power loss of the proposed ODSG-TMOS is 77.0% lower than that of the Con-ATMOS. In addition, the SOA of the proposed device is also enhanced. The saturation drain current(Id,sat) at a gate voltage(Vgs) of 15 V for the ODSGTMOS is reduced by 17.2% owing to the JFET effect provided by the lower shield gate(SG) at a large drain voltage. With the reduced Id,sat, the short-circuit withstand time is improved by 87.5% compared with the Con-ATMOS. The large-current turn-off capability is also improved, which is important for the widely used inductive load applications.展开更多
An analytical breakdown model under on state condition for high voltage RESURF LDMOS is proposed.The model considers the drift velocity saturation of carriers and influence of parasitic bipolar transistor.As a result...An analytical breakdown model under on state condition for high voltage RESURF LDMOS is proposed.The model considers the drift velocity saturation of carriers and influence of parasitic bipolar transistor.As a result,electric field profile of n drift in LDMOS at on state is obtained.Based on this model,the electric SOA of LDMOS can be determined.The analytical results partially fit to our numerical (by MEDICI) and experiment results.This model is an aid to understand the device physics during on state accurately and it also directs high voltage LDMOS design.展开更多
As a crucial infrastructure in the transport system,the safe operation of bridges is directly related to all aspects of people’s daily lives.The development of bridge structural health monitoring technology and its a...As a crucial infrastructure in the transport system,the safe operation of bridges is directly related to all aspects of people’s daily lives.The development of bridge structural health monitoring technology and its application play an important role in ensuring the safety and extending the service life of bridges.This paper carries out in-depth research and analysis on the related technology of bridge structural health monitoring.Firstly,the existing monitoring technologies at home and abroad are sorted out,and the advantages and problems of various methods are compared and analyzed,including nondestructive testing,stress measurement,vibration characteristic identification,and other commonly used monitoring technologies.Secondly,the key technologies and equipment in the bridge health monitoring system,such as sensor technology,data acquisition,and processing technology,are introduced in detail.Finally,the development trend in the field of bridge health monitoring is prospected from both theoretical research and technical application.In the future,with the development of emerging technologies such as big data,cloud computing,and the Internet of Things,it is expected that bridge health monitoring with intelligent and systematic features will be more widely applied to provide a stronger guarantee for the safe and efficient operation of bridges.展开更多
A new transportation technology known as personal rapid transit （PRT） is being developed by multiple different companies around the world, and one system is under commercial operations in the United Kingdom. Each de...A new transportation technology known as personal rapid transit （PRT） is being developed by multiple different companies around the world, and one system is under commercial operations in the United Kingdom. Each design is different, but they all share a need to operate many automated transit vehicles at very close headways. Safe operation will require a level of control an order of magnitude above any current transit system. As a result, new techniques will be needed for the development and testing of the mechanical and control systems. In this paper an apparatus for developing and testing a PRT vehicle control scheme is demonstrated. This system is composed of independent modules that represent virtual vehicles, a central control system, a man-machine interface and a monitoring device. It can be used to implement and to evaluate the designed vehicle control algorithm. The vehicle control algorithm is designed and simulated in a combined simulation platform that consists of Matlab/Simulink and Labview Simulation Interface Toolkit. Simple operational scenarios are proposed for the testing of the proposed vehicle control apparatus.展开更多
Gas has brought convenience to people’s life at present, and gas pipeline networks and ancillary facilities play important roles in city construction. However, there are increasingly prominent safety problems in oper...Gas has brought convenience to people’s life at present, and gas pipeline networks and ancillary facilities play important roles in city construction. However, there are increasingly prominent safety problems in operation. The safe operation of gas pipeline networks in cities has been influenced by various aspects of factors, leading to frequent gas accidents, which give rise to serious influences on supply of gas. For this reason, detailed analysis has been conducted to problems related to safe operation of gas pipeline networks in cities in this article, and corresponding solutions are proposed.展开更多
Returning home is the most important process of a parallel kinematic machine(PKM)with incremental encoders.Currently,most corresponding articles focus on the accuracy of homing process,and there lacks the investigatio...Returning home is the most important process of a parallel kinematic machine(PKM)with incremental encoders.Currently,most corresponding articles focus on the accuracy of homing process,and there lacks the investigation of the operation's safety.For a 4RRR PKM,all servoaxes would be independently driven to their zero positions at the same time based on the traditional homing mode,and that can bring serious interfere of the kinematic chains.This paper systemically investigates this 4RRR PKM's safety of homing process.A homing strategy usually contains three parts which are the home switches'locations,the platform's initial moving space,and each links'homing direction,and all of them can influence the safety of homing operation.For the purpose of evaluating and describing the safety of the homing strategy,some important parameters are introduced as follows:Safely homing ratio(SHR)is used to evaluate the probability of a machine's successfully returning home from an initial moving space;Synchronal rotational angle(SRA)is the four links'largest synchronal rotational angle with given directions from a given pose.Whether a machine can safely return home from a given pose can be judged by comparing the SRA with all four home switches'mounting angles.By meshing the initial moving space and checking the safeties of returning home from all the initial poses on the nodes,the SHR of this initial moving space can be calculate.For the sake of convenience,the platform's initial moving space should be as large as possible,and in this 4RRR PKM,a square zone in the center of the workspace with a giving initial rotation range is selected as the platform's initial moving space.The forward direction is selected as each link's homing direction according to custom,and the platform's initial rotational angle is selected as larger than 0°based on this 4RRR PKM's kinematic characteristics.The platform's initial moving space can be defined only by the side length of the initial moving square.By setting a probable searching step and calculating the SHR of the initial moving square,an optimal procedure of searching for the largest side length of the platform's initial moving square is proposed.The homing strategy proposed is based on a systemic research on the safety of homing process for PKM,and the two new indexes SHR and SRA can clearly describe the safety of homing operation.The homing operation based on this strategy is fast and safe,and the method can also be used in other PKMs with the situation of serious components'interference.展开更多
基金supported by the Key Program of National Natural Science Foundation of China“Research on risk formation mechanism and control method of oil&gas storage and transportation system from the perspective of cyber-physics”(No:52234007).
文摘Oil and gas production systems have the characteristics of high operation and maintenance risk and great accident influence.With the deep integration of informationization and industrialization,the development direction and necessary choice of the oil and gas industry is to develop the oil and gas production system into the interconnected,multi-domain interactive cyber-physical intelligent system.In order to avoid or reduce the complex,diverse and potentially unknown safety risks in the process of oil and gas production,improve the safety and reliability of oil and gas production system and increase the production efficiency,this paper analyzes the safety problems occurring in the intelligentization process of oil and gas production system and constructs a system from the perspective of operation and maintenance based on key elements of intelligent safe operation and maintenance technology,combined with the typical production scenarios in the oil and gas production industry.And the following research results are obtained.First,the connotation of intelligent safe operation and maintenance technology is clarified,the key elements and existing problems and challenges of intelligent safe operation and maintenance technology are analyzed,and the“1-2-3-4-5-6”intelligent safe operation and maintenance technology system of oil and gas production system is constructed,which empowers six key technologies with key elements of oil and gas production to realize the essential safety of oil and gas production system.Second,the intelligent safe operation and maintenance technology actively promotes the application and implementation of condition monitoring,health management,risk assessment,intelligent early warning technologies in typical production scenarios such as drilling and extraction,storage and transportation,refining and chemical industry in up,middle and down streams of oil and gas production.Third,in view of the characteristics of oil and gas production system under digital transformation,it is proposed to develop the intelligent safe operation and maintenance technology with the functions of intelligent decision-making,active prevention and comprehensive safety in the future to help the safe construction in thefield of oil and gas production and promote the safe and healthy development of the oil and gas industry.In conclusion,the research on intelligent safe operation and maintenance technology system of oil and gas production system is conducive to the safe construction in thefield of oil and gas production,which will not only provide technical support for the realization of trouble-free oil and gas production system,but also provide reference for the intelligent development of the world oil and gas industry.
文摘Transmission and distribution line is an important part of the grid system, therefore, in the grid planning and design, transmission and distribution line occupies a very important position, in order to ensure the normal and safe operation of the power system grid, need to focus on the planning and design of the grid system of transmission and distribution line safe operation. This paper mainly introduces the current situation of transmission and distribution lines in the power system planning and design and the countermeasures to realize its safe operation, which is of great significance to promote the power system planning and design in China.
文摘On May 1st, China National Nuclear Corporation(CNNC) announced in Beijing that unit 1 and unit 2 ofTianwan Nuclear Power Plant cooperatively constructedby China and Russia have completed in succession thefirst fuel cycle operation continuously and safely. It is
文摘As an important basic tool for power transmission, most of the overhead transmission lines are exposed to the natural environment, the design and construction methods are different. And there are many man-made damage factors during operation, which reduce the normal operation capacity of the transmission line, and cause the fault that the line can not transmit electric energy, The safety status of the overhead transmission line itself is not only related to the overall development of the power industry, but also has an important impact on the power users. Therefore, it is quite necessary to identify, analyze and evaluate the risks in the operation system of the transmission line, which can provide the basis for the adjustment of equipment, operation management, operation and maintenance, so as to eliminate and control the risk factors existing in the transmission line system and minimize the occurrence of accidents. So as to achieve the best safe operation state.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51209233,51179209)the Special Scientific Research Fund of Public Welfare Profession of China(Grant No.1261530110135)the National Basic Research Development Program of China(973 Program,Grant No.2013CB036405)
文摘Sixteen inverted siphons are in operation at the Beijing-Shijiazhuang section in the Middle Route of the South-to-North Water Diversion Project. Their safe operation is closely related to the safety and the water diversion efficiency of the whole project during an ice period. The ice accumulation process at the inlet of the inverted siphon is modeled under a real ice condition, and then the hydraulic conditions of the ice jam prevention are confirmed. According to the experimental results and the design sizes of the inverted siphons, the detailed safe water diversion discharge and the operational water level are studied. Analysis results of these inverted siphons provide references for the safe operation and the reasonable regulations during the ice period.
基金supported by grants from the National Natural Science Foundation of China 51178157High-level Project of the Top Six Talents in Jiangsu Province JXQC-021+1 种基金the Key Science and Technology Program in Henan Province 182102310004the Postgraduate Research and Prac-tice Innovation Program of Jiangsu Province KYCX20-0290.
文摘In this paper,the least square support vector machine(LSSVM)is used to study the safety of a high-speed railway.According to the principle of LSSVM regression prediction,the parameters of the LSSVM are optimized to model the natural disaster early warning of safe operation of a high-speed railway,and the management measures and methods of high-speed railway safety operation under natural disasters are given.The relevant statistical data of China’s high-speed railway are used for training and verification.The experimental results show that the LSSVM can well reflect the nonlinear relationship between the accident rate and the influencing factors,with high simulation accuracy and strong generalization ability,and can effectively predict the natural disasters in the safe operation of a high-speed railway.Moreover,the early warning system can improve the ability of safety operation evaluation and early warning of high-speed railway under natural disasters,realize the development goals of high-speed railway(safety,speed,economic,low-carbon and environmental protection)and provide a theoretical basis and technical support for improving the safety of a high-speed railway.
文摘The navigation enterprise has no fixed business, no stable customers, even no stable operation team, poor technical strength, poor profitability, poor economic strength, nonstandard management, etc., and there are great risks in safe flight operation. For small-scale navigation enterprises, it is very important to ensure the safe and stable operation of aircraft, which is a core asset. How to ensure the safe and healthy operation of the maintenance system of small-scale navigation enterprises by means of management is the main research direction of this paper. Based on the idea of project management, this paper explores the safe and healthy operation of the maintenance system in small-scale navigation enterprises.
文摘Electric power, as one of the basic elements of social operation, promotes the economic development of various places, and the importance of power plants is self-evident. Whether the power plant can work efficiently and maintain the quality of output will affect the stability of power. So the safety of power plant must be paid attention to. In safety management, we should pay special attention to the emergency problems. We should prepare the corresponding countermeasures to solve the unexpected accidents and minimize the losses. This kind of safety management is complete enough to ensure the safe operation of the power plant.
文摘Urban gas projects play an important role in the development of urbanization in China. The safe construction and management of urban gas production and operation have great influence on the safe use and quality of urban gas. In the process of urbanization, the continuous construction and development of gas engineering not only greatly promotes the development of society, but also greatly facilitates people's daily production and life. However, it also has some security risks. Therefore, it is necessary to give high priority to urban gas engineering construction and safe production operation management, comprehensively utilize daily operation management, institutional safety and high-tech capabilities, and effectively improve the safety of urban gas production operation.
基金supported by the National Natural Science Foundation of China(Grant No.42101296)the Natural Science Foundation of Chongqing(Grant No.CSTB2023NSCQ-MSX0041)Chongqing Municipal Training Program of Innovation and Entrepreneurship Project(Grants No.S202410635155 and X202410635116)。
文摘Safe and just operating spaces(SJOS)are influenced by complex cross-scale interactions and cascading effects spanning global,regional,and local landscape scales.However,existing SJOS research has often focused on single-scale assessments,overlooking the impacts of multiscale interactions and within-region heterogeneity on urban SJOS.To address this gap,we developed a cross-scale framework for assessing urban SJOS,explicitly incorporating top-down influences from upper-level constraints and bottom-up effects from lower-level heterogeneity.This approach was applied to China's five major metropolises to examine the states and cross-scale dynamics influencing urban SJOS between 1990 and 2020.Our findings reveal that the SJOS of China's metropolises were primarily influenced by factors at national and local landscape scales,with weaker influences from the global and continental scales.A persistent trade-off between social justice and environmental safety was identified across spatiotemporal scales.For instance,Chongqing in southwestern China lagged behind the eastern four metropolises in social performance but exhibited stronger environmental safety due to its extensive natural landscapes,which mitigated the anthropogenic impacts of urban centers.Regional issues,such as the overshoot of PM_(2.5)and ecological footprints(EF),were primarily driven by the bottom-up accumulation of localized pressures,while the overshoot of CO_(2)was attributed to national policy constraints and the universal exceedance of safe thresholds across scales.Addressing urban sustainability requires avoiding adverse cascading effects from other levels by emphasizing landscape heterogeneity within metropolises and fostering coordinated collaboration across scales,particularly at the regional landscape and national levels.
文摘[Objective]This study aims to investigate the multi-body hydrodynamic interaction mechanisms during offshore lifting operations of aquaculture net cages in wind-fishery integration systems.By integrating numerical simulations and dynamic analysis methods,this study systematically investigates the coupled dynamic response characteristics during the cage-carrier vessel separation process to reveal its dynamic evolution patterns and key influence mechanisms.[Method]Based on potential flow theory,a fully coupled dynamic analysis model of crane vessel-net cage-semi-submersible barge was established for a marine ranch project in Guangdong.The complete lifting process was dynamically simulated using SESAM software.Five typical operating sea states were configured to investigate the influence of wave parameters on the system's motion response under combined wave-current-wind actions.[Result]The results demonstrate that wave period dominates the system stability.Under short-period conditions,the system maintains stable motion with relatively small horizontal relative displacements,while long-period conditions excite low-frequency resonance,leading to significant slow-drift motions.Vertical response analysis reveals that long-period waves cause severe relative displacement fluctuations between the cage and semi-submersible vessel,with actual displacement amplitudes doubling the preset safety target of 2.045 m.Quantitative analysis further indicates that when significant wave height increases from 1.0 m to 1.5 m,the actual displacement amplitude increases by approximately 20%relative to the target displacement of 2.045 m,demonstrating that its influence is significantly weaker than the displacement variations induced by wave period changes.The complete dynamic simulation successfully captures the continuous dynamic response characteristics during the lifting process.[Conclusion]This research clarifies the influence mechanisms of wave parameters on the cage lifting process,identifying wave period as the crucial factor for operational safety.An operation window assessment method incorporating multi-body coupling effects is established,proposing a safety criterion with peak period not exceeding six seconds as the core requirement.The findings provide theoretical foundation for safe installation of marine ranch net cages and offer valuable references for similar offshore lifting operations.
基金The authors would like to thank National Nature Science Foundation of China under Grant(71701202)The special funding project of Civil Aviation University of China for the basic scientific research services of the Central University(3122013Z006).
文摘In order to explore the safe operation of UAVs in non-segregated airspace,a collision risk model for cylindrical UAVs based on conflict areas was constructed and the risk of conflict between manned and unmanned aerial vehicles was researched.According to the results of risk analysis,a strategy for solving the conflict of aircraft is proposed,and the risk assessment experiment of unmanned aerial vehicle(UAV)in non-isolated airspace conflict is carried out.The results show that under the experimental conditions,large unmanned aerial vehicles equipped with ADS-B,TCAS and other airborne sensing systems will indeed interfere with other aircraft in airspace when they enter non-isolated airspace.Especially when the number of aircraft in airspace is large,the automatic avoidance system of UAV will increase the avoidance time and trigger the safety alarm,but the safety level is still acceptable.This indicates that it is relatively safe for UAVs to enter non-isolated airspace under limited conditions.The results can be used as a reference for the safe operation of unmanned aerial vehicle(UAV)in non-isolated airspace.
文摘With the over-exploitation of traditional energy sources such as coal and oil and the advent of the world energy crisis, new energy sources such as wind and solar energy have attracted more and more attention from the world. New energy can not only alleviate the energy crisis, but also can be more environmentally friendly than traditional energy, and it can be recycled for a long time. Wind energy is an important form of wind energy utilization. It is one of the renewable energy projects with the most mature technology, the largest scale of development, and the broadest prospects for commercial development. Wind energy is a pollution-free, renewable and mature technology, so it is very popular. At present, there are hidden dangers in the operation management and technical quality of wind farms, which affect the safe operation of wind turbines. This paper studied the safe operation and control technology of direct drive wind turbines, analyzed the operation that affects safety, and provided a solution to solve this problem. The safe operation of the equipment during the entire life cycle ensures its rapid development.
基金Project supported by the China Postdoctoral Science Foundation (Grant No. 2020M682607)。
文摘A novel silicon carbide(SiC) trench metal–oxide–semiconductor field-effect transistor(MOSFET) with a dual shield gate(DSG) and optimized junction field-effect transistor(JFET) layer(ODSG-TMOS) is proposed. The combination of the DSG and optimized JFET layer not only significantly improves the device’s dynamic performance but also greatly enhances the safe operating area(SOA). Numerical analysis is carried out with Silvaco TCAD to study the performance of the proposed structure. Simulation results show that comparing with the conventional asymmetric trench MOSFET(Con-ATMOS), the specific on-resistance(Ron,sp) is significantly reduced at almost the same avalanche breakdown voltage(BVav). Moreover, the DSG structure brings about much smaller reverse transfer capacitance(Crss) and input capacitance(Ciss), which helps to reduce the gate–drain charge(Qgd) and gate charge(Qg). Therefore, the high frequency figure of merit(HFFOM) of Ron,sp·Qgdand Ron,sp· Qgfor the proposed ODSG-TMOS are improved by 83.5% and 76.4%, respectively.The switching power loss of the proposed ODSG-TMOS is 77.0% lower than that of the Con-ATMOS. In addition, the SOA of the proposed device is also enhanced. The saturation drain current(Id,sat) at a gate voltage(Vgs) of 15 V for the ODSGTMOS is reduced by 17.2% owing to the JFET effect provided by the lower shield gate(SG) at a large drain voltage. With the reduced Id,sat, the short-circuit withstand time is improved by 87.5% compared with the Con-ATMOS. The large-current turn-off capability is also improved, which is important for the widely used inductive load applications.
文摘An analytical breakdown model under on state condition for high voltage RESURF LDMOS is proposed.The model considers the drift velocity saturation of carriers and influence of parasitic bipolar transistor.As a result,electric field profile of n drift in LDMOS at on state is obtained.Based on this model,the electric SOA of LDMOS can be determined.The analytical results partially fit to our numerical (by MEDICI) and experiment results.This model is an aid to understand the device physics during on state accurately and it also directs high voltage LDMOS design.
文摘As a crucial infrastructure in the transport system,the safe operation of bridges is directly related to all aspects of people’s daily lives.The development of bridge structural health monitoring technology and its application play an important role in ensuring the safety and extending the service life of bridges.This paper carries out in-depth research and analysis on the related technology of bridge structural health monitoring.Firstly,the existing monitoring technologies at home and abroad are sorted out,and the advantages and problems of various methods are compared and analyzed,including nondestructive testing,stress measurement,vibration characteristic identification,and other commonly used monitoring technologies.Secondly,the key technologies and equipment in the bridge health monitoring system,such as sensor technology,data acquisition,and processing technology,are introduced in detail.Finally,the development trend in the field of bridge health monitoring is prospected from both theoretical research and technical application.In the future,with the development of emerging technologies such as big data,cloud computing,and the Internet of Things,it is expected that bridge health monitoring with intelligent and systematic features will be more widely applied to provide a stronger guarantee for the safe and efficient operation of bridges.
文摘A new transportation technology known as personal rapid transit （PRT） is being developed by multiple different companies around the world, and one system is under commercial operations in the United Kingdom. Each design is different, but they all share a need to operate many automated transit vehicles at very close headways. Safe operation will require a level of control an order of magnitude above any current transit system. As a result, new techniques will be needed for the development and testing of the mechanical and control systems. In this paper an apparatus for developing and testing a PRT vehicle control scheme is demonstrated. This system is composed of independent modules that represent virtual vehicles, a central control system, a man-machine interface and a monitoring device. It can be used to implement and to evaluate the designed vehicle control algorithm. The vehicle control algorithm is designed and simulated in a combined simulation platform that consists of Matlab/Simulink and Labview Simulation Interface Toolkit. Simple operational scenarios are proposed for the testing of the proposed vehicle control apparatus.
文摘Gas has brought convenience to people’s life at present, and gas pipeline networks and ancillary facilities play important roles in city construction. However, there are increasingly prominent safety problems in operation. The safe operation of gas pipeline networks in cities has been influenced by various aspects of factors, leading to frequent gas accidents, which give rise to serious influences on supply of gas. For this reason, detailed analysis has been conducted to problems related to safe operation of gas pipeline networks in cities in this article, and corresponding solutions are proposed.
基金supported by National Natural Science Foundation of China(Grant No.50775125,and No.50775117)National Hi-tech Research and Development Program of China(863 Program,Grant No.2007AA041901)National Basic Research Program of China(973 Program,Grant No.2004CB318007)
文摘Returning home is the most important process of a parallel kinematic machine(PKM)with incremental encoders.Currently,most corresponding articles focus on the accuracy of homing process,and there lacks the investigation of the operation's safety.For a 4RRR PKM,all servoaxes would be independently driven to their zero positions at the same time based on the traditional homing mode,and that can bring serious interfere of the kinematic chains.This paper systemically investigates this 4RRR PKM's safety of homing process.A homing strategy usually contains three parts which are the home switches'locations,the platform's initial moving space,and each links'homing direction,and all of them can influence the safety of homing operation.For the purpose of evaluating and describing the safety of the homing strategy,some important parameters are introduced as follows:Safely homing ratio(SHR)is used to evaluate the probability of a machine's successfully returning home from an initial moving space;Synchronal rotational angle(SRA)is the four links'largest synchronal rotational angle with given directions from a given pose.Whether a machine can safely return home from a given pose can be judged by comparing the SRA with all four home switches'mounting angles.By meshing the initial moving space and checking the safeties of returning home from all the initial poses on the nodes,the SHR of this initial moving space can be calculate.For the sake of convenience,the platform's initial moving space should be as large as possible,and in this 4RRR PKM,a square zone in the center of the workspace with a giving initial rotation range is selected as the platform's initial moving space.The forward direction is selected as each link's homing direction according to custom,and the platform's initial rotational angle is selected as larger than 0°based on this 4RRR PKM's kinematic characteristics.The platform's initial moving space can be defined only by the side length of the initial moving square.By setting a probable searching step and calculating the SHR of the initial moving square,an optimal procedure of searching for the largest side length of the platform's initial moving square is proposed.The homing strategy proposed is based on a systemic research on the safety of homing process for PKM,and the two new indexes SHR and SRA can clearly describe the safety of homing operation.The homing operation based on this strategy is fast and safe,and the method can also be used in other PKMs with the situation of serious components'interference.
