[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
As carrier aircraft sortie frequency and flight deck operational density increase,autonomous dispatch trajectory planning for carrier-based vehicles demands efficient,safe,and kinematically feasible solutions.This pap...As carrier aircraft sortie frequency and flight deck operational density increase,autonomous dispatch trajectory planning for carrier-based vehicles demands efficient,safe,and kinematically feasible solutions.This paper presents an Iterative Safe Dispatch Corridor(iSDC)framework,addressing the suboptimality of the traditional SDC method caused by static corridor construction and redundant obstacle exploration.First,a Kinodynamic-Informed-Bidirectional Rapidly-exploring Random Tree Star(KIBRRT^(*))algorithm is proposed for the front-end coarse planning.By integrating bidirectional tree expansion,goal-biased elliptical sampling,and artificial potential field guidance,it reduces unnecessary exploration near concave obstacles and generates kinematically admissible paths.Secondly,the traditional SDC is implemented in an iterative manner,and the obtained trajectory in the current iteration is fed into the next iteration for corridor generation,thus progressively improving the quality of withincorridor constraints.For tractors,a reverse-motion penalty function is incorporated into the back-end optimizer to prioritize forward driving,aligning with mechanical constraints and human operational preferences.Numerical validations on the data of Gerald R.Ford-class carrier demonstrate that the KIBRRT^(*)reduces average computational time by 75%and expansion nodes by 25%compared to conventional RRT^(*)algorithms.Meanwhile,the iSDC framework yields more time-efficient trajectories for both carrier aircraft and tractors,with the dispatch time reduced by 31.3%and tractor reverse motion proportion decreased by 23.4%relative to traditional SDC.The presented framework offers a scalable solution for autonomous dispatch in confined and safety-critical environment,and an illustrative animation is available at bilibili.com/video/BV1tZ7Zz6Eyz.Moreover,the framework can be easily extended to three-dimension scenarios,and thus applicable for trajectory planning of aerial and underwater vehicles.展开更多
The Hainan FTP is a game changer,and those who seize the opportunities it offers early will be in an advantageous position As it provides a vital new model for China’s international trade and logistics,the Hainan Fre...The Hainan FTP is a game changer,and those who seize the opportunities it offers early will be in an advantageous position As it provides a vital new model for China’s international trade and logistics,the Hainan Free Trade Port(FTP)stands out among similar opening-up initiatives.展开更多
The utilization and storage of CO_(2) emissions from oil production and consumption in the upstream oil industry will contribute to sustainable development.CO_(2) flooding is the key technology for the upstream oil in...The utilization and storage of CO_(2) emissions from oil production and consumption in the upstream oil industry will contribute to sustainable development.CO_(2) flooding is the key technology for the upstream oil industry to transition to sustainable development.However,there is a significant challenge in achieving high recovery and storage efficiency in unconventional reservoirs,particularly in underde-veloped countries.Numerous studies have indicated that the limited sweep range caused by premature gas channeling of CO_(2) is a crucial bottleneck that hinders the enhancement of recovery,storage efficiency and safety.This review provides a comprehensive summary of the research and technical advancements regarding the front sweep characteristics of CO_(2) during migration.It particularly focuses on the char-acteristics,applicable stages,and research progress of different technologies used for regulating CO_(2) flooding sweep.Finally,based on the current application status and development trends,the review offers insights into the future research direction for these technologies.It is concluded that the front migration characteristics of CO_(2) play a crucial role in determining the macroscopic sweep range.The focus of future research lies in achieving cross-scale correlation and information coupling of CO_(2) migration processes.Currently,the influence weight of permeability,injection speed,pressure and other parameters on the characteristics of‘fingering-gas channeling’is still not well clear.There is an urgent need to establish prediction model and early warning mechanism that considers multi-parameters and cross-scale gas channeling degrees,in order to create effective strategies for prevention and control.There are currently three technologies available for sweep regulation:flow field intervention,mobility reduction,and gas channeling plugging.To expand the sweep effectively,it is important to systematically integrate these technologies based on their regulation characteristics and applicable stages.This can be achieved by constructing an intelligent synergistic hierarchical segmented regulation technology known as‘flow field intervention+mobility regulation+channel plugging chemically’.This work is expected to provide valuable insights for achieving conformance control of CO_(2)-EOR and safe storage of CO_(2).展开更多
Generating dynamically feasible trajectory for fixed-wing Unmanned Aerial Vehicles(UAVs)in dense obstacle environments remains computationally intractable.This paper proposes a Safe Flight Corridor constrained Sequent...Generating dynamically feasible trajectory for fixed-wing Unmanned Aerial Vehicles(UAVs)in dense obstacle environments remains computationally intractable.This paper proposes a Safe Flight Corridor constrained Sequential Convex Programming(SFC-SCP)to improve the computation efficiency and reliability of trajectory generation.SFC-SCP combines the front-end convex polyhedron SFC construction and back-end SCP-based trajectory optimization.A Sparse A^(*)Search(SAS)driven SFC construction method is designed to efficiently generate polyhedron SFC according to the geometric relation among obstacles and collision-free waypoints.Via transforming the nonconvex obstacle-avoidance constraints to linear inequality constraints,SFC can mitigate infeasibility of trajectory planning and reduce computation complexity.Then,SCP casts the nonlinear trajectory optimization subject to SFC into convex programming subproblems to decrease the problem complexity.In addition,a convex optimizer based on interior point method is customized,where the search direction is calculated via successive elimination to further improve efficiency.Simulation experiments on dense obstacle scenarios show that SFC-SCP can generate dynamically feasible safe trajectory rapidly.Comparative studies with state-of-the-art SCP-based methods demonstrate the efficiency and reliability merits of SFC-SCP.Besides,the customized convex optimizer outperforms off-the-shelf optimizers in terms of computation time.展开更多
Due to the influence of karst cave development and route selection,the location relationship between concealed karst cave and tunnel is more random.In order to explore the influence rule of karst cave location on the ...Due to the influence of karst cave development and route selection,the location relationship between concealed karst cave and tunnel is more random.In order to explore the influence rule of karst cave location on the minimum safe thickness of water-proof rock mass,a simplified calculation model of water-proof rock mass thickness when the karst cave is located at any location around the tunnel is established,and the influence of multiple factors on the overall stability of water-proof rock mass is considered.Based on the cusp catastrophe theory,the analytical expressions for the safety thickness of waterproof rock mass are derived.Based on the finite difference principle,the analytical expressions of the safety thickness of water-proof rock mass are verified.In order to improve the application range of the analytical formula derived in this paper,the analytical formula is optimized based on the instability principle differences between the simplified calculation model and the elastic compressive bar.The research results show that the necessary condition solution is more applicable and much safer than the sufficient condition solution.Tectonic stress,rock beam length and karst cave water pressure are significantly positively correlated with the safe thickness of the waterproof rock mass.The calculated results of the semioptimized formula and the unoptimized formula are constant values,independent of the karst cave location.While the calculated results of the fully optimized formula are variable values,correlated with the karst cave location,the thickness of the waterproof rock mass gradually decreases as the karst cave location moves from the top of the tunnel to the bottom of the tunnel.The unoptimized formula does not consider the influence of the lateral force of the rock beam,and is not suitable for the working condition with large lateral force,the calculation results of the semi-optimized formula and the fully optimized formula are not very different and are biased to safety,so it can be given priority.展开更多
Grasping is one of the most fundamental operations in modern robotics applications.While deep rein-forcement learning(DRL)has demonstrated strong potential in robotics,there is too much emphasis on maximizing the cumu...Grasping is one of the most fundamental operations in modern robotics applications.While deep rein-forcement learning(DRL)has demonstrated strong potential in robotics,there is too much emphasis on maximizing the cumulative reward in executing tasks,and the potential safety risks are often ignored.In this paper,an optimization method based on safe reinforcement learning(Safe RL)is proposed to address the robotic grasping problem under safety constraints.Specifically,considering the obstacle avoidance constraints of the system,the grasping problem of the manipulator is modeled as a Constrained Markov Decision Process(CMDP).The Lagrange multiplier and a dynamic weighted mechanism are introduced into the Proximal Policy Optimization(PPO)framework,leading to the development of the dynamic weighted Lagrange PPO(DWL-PPO)algorithm.The behavior of violating safety constraints is punished while the policy is optimized in this proposed method.In addition,the orientation control of the end-effector is included in the reward function,and a compound reward function adapted to changes in pose is designed.Ultimately,the efficacy and advantages of the suggested method are proved by extensive training and testing in the Pybullet simulator.The results of grasping experiments reveal that the recommended approach provides superior safety and efficiency compared with other advanced RL methods and achieves a good trade-off between model learning and risk aversion.展开更多
Since its introduction as a decentralized digital currency for peer-to-peer transactions,Bitcoin’s role in financial markets has undergone significant evolution.We employ bibliometric analysis to explore research tre...Since its introduction as a decentralized digital currency for peer-to-peer transactions,Bitcoin’s role in financial markets has undergone significant evolution.We employ bibliometric analysis to explore research trends in Bitcoin,identifying two primary perspectives in the recent financial economic literature:Bitcoin as a speculative asset and as a safe-haven asset.The speculative nature of Bitcoin is evident through its high volatility and frequent price jumps,largely influenced by rapid shifts in investor sentiment and attention,which create both risks and opportunities for traders.Conversely,Bitcoin exhibits characteristics of a safe-haven asset due to its asymmetric tail dependence and negative correlation within certain asset classes.展开更多
Urbanization develops with the goal of establishing improved and more sustainable habitats for residents.Environmental and social performance must be simultaneously monitored to ascertain whether regions are progressi...Urbanization develops with the goal of establishing improved and more sustainable habitats for residents.Environmental and social performance must be simultaneously monitored to ascertain whether regions are progressing towards or deviating from the safe and just space(SJS)in urbanization.Despite relevant studies,the absence of indicators that bridge ecological preservation and human well-beings renders dual monitoring challenging.This study bridged the gap by exploring the interactions between urbanization,ecosystem services(ESs),and basic water,energy,and food(WEF)needs within the SJS framework across China and its provinces.By quantifying the minimum and actual demands for freshwater withdrawal,carbon emissions,phosphorus emissions,and land use,as well as the supply of ESs into unified biophysical indicators,we found that:(1)China can meet the basic WEF needs for all from 2000 to 2020,but only water and land provisioning ESs can operate within the SJS.Carbon emissions surpassed the sequestration capacity in 2010,while phosphorus purification ES has consistently been unsafe.(2)The SJS performance in terms of ecological and social fulfilment exhibited scale differences and undergone changes with urbanization.Overall,no province in China can consistently operate within all SJSs.(3)In the process of urbanization,improvements in ecological protection and production practices in most provinces expanded the size of SJS,but the continuous increase in total demand failed to steer regions toward safer spaces.Our framework emphasized the common but differentiated pathways that regions at varying stages of urbanization navigate to achieve safety and justice.It also provides an applicable solution for regions aiming to pursue urban growth while maintaining ecological conservation and social justice,ultimately achieving sustainable development.展开更多
Hydropol a water-soluble,marine-safe,non-toxic polymer,is set to revolutionize the manufacture of hygiene products,suchas wet wipes and sanitary pads by making them dissolvable,fulyflushable and preventing them from f...Hydropol a water-soluble,marine-safe,non-toxic polymer,is set to revolutionize the manufacture of hygiene products,suchas wet wipes and sanitary pads by making them dissolvable,fulyflushable and preventing them from forming fatbergs in sewers andreleasing harmful microplastics.This is thanks to the developmentof a revolutionary new dissolvable nonwoven material(flat,poroussheets that are made directly from separate filbres or from moltenplastic or plastic film)which uses Hydropol instead of conventionalplastics and helps prevent tonnes of plastic pollution from enteringthe environment.展开更多
Objective:Nurses must follow safe injection practices to prevent healthcare-associated infections(HAIs).This study aimed to identify the risk factors for safe injection practice among nurses in general hospitals.Metho...Objective:Nurses must follow safe injection practices to prevent healthcare-associated infections(HAIs).This study aimed to identify the risk factors for safe injection practice among nurses in general hospitals.Methods:This cross-sectional study included 215 nurses employed in Korean general hospitals.Data were collected from September 22 to October 9,2023.Multiple linear regression analysis was performed using SPSS Statistics 27.0.Results:The regression analysis revealed that a higher level of patient safety priority in the patient safety culture perception,increased knowledge of safe injection practices,and fewer working hours per week were associated with improved performance of safe injection practices among general hospital nurses.Conclusions:To enhance the performance of general hospital nurses in safe injection practice,it is necessary to establish a patient safety culture so that nurses recognize patient safety as a top priority.Additionally,an effective educational program is needed to increase the practical knowledge of safe injection practices,along with a supportive working environment that ensures appropriate working hours to prevent patient safety incidents.展开更多
Investing in cryptocurrencies is progressively becoming a norm;however,these assets are excessively volatile and often decrease or increase in value instantly.Thus,rational investors holding cryptocurrencies for exten...Investing in cryptocurrencies is progressively becoming a norm;however,these assets are excessively volatile and often decrease or increase in value instantly.Thus,rational investors holding cryptocurrencies for extended periods firmly search for assets that can diversify their risk,preferably with assets other than cryptocurrencies.In this study,we consider the two most studied cryptocurrencies with the highest capitalization and trading volume/value,namely Bitcoin and Ethereum.Specifically,we examine whether high-performing leading US tech stocks(Facebook,Amazon,Apple,Netflix,Google[FAANG])can provide any diversification benefits to cryptocurrency investors.To do so,we employ dynamic conditional correlation(DCC),asymmetric DCC,time-varying parameter vector autoregression-based connectedness measures,dynamic correlation-based hedge and safe-haven regression analyses,portfolio optimization and hedging strategies,time-and frequency-based wavelet coherence,and high-frequency 10-min intraday data from January 1,2018 to January 31,2023.We find that FAANG stocks can be considered(at least weak)safe havens for Bitcoin and Ethereum during the sample period.Our subperiod analyses reveal that the safehaven role of FAANG stocks,specifically for Bitcoin,has noticeably increased.While the safe-haven property of Facebook is the most promising,for Netflix it is blurred between a weak–safe-haven and a hedge.Our findings may help investors,policymakers,and academicians to invest in cryptocurrencies,formulate relevant investment guidelines,and extend the literature on cryptocurrencies,respectively.展开更多
With the increasingly turbulent political situation and the outbreak of public health events without warning,it will not only affect people’s physical health,but also affect the global financial market,causing the ma...With the increasingly turbulent political situation and the outbreak of public health events without warning,it will not only affect people’s physical health,but also affect the global financial market,causing the market to fall into a huge crisis,thus leading to a continued decline in the worldwide economy.During periods of financial market turmoil,many investors fall into panic and urgently need a“haven”to protect their assets.With the rise of the digital economy,gold no longer seems to be the only safe-haven option.Bitcoin has gradually entered the investors’field of vision.Some investors believe that Bitcoin can become an emerging safe-haven asset that is as important as or surpasses gold.Based on an analysis of the safe-haven properties of Bitcoin and gold during major political and historical events and public health events,this article will clarify which of the two is more suitable as a reliable contemporary safe-haven asset and provide advice to investors.展开更多
Objective:To explore the application effect of bundle management in the safe nursing of patients with autoimmune encephalitis.Methods:Seventy-five patients with autoimmune encephalitis who met the inclusion criteria i...Objective:To explore the application effect of bundle management in the safe nursing of patients with autoimmune encephalitis.Methods:Seventy-five patients with autoimmune encephalitis who met the inclusion criteria in our hospital from January 2024 to June 2024 were randomly divided into two groups:an observation group of 39 patients and a control group of 36 patients.The control group received routine nursing care,while the observation group implemented a bundle management strategy based on routine nursing care.Safety nursing outcomes,clinical symptom improvement time,hospital stay,and neurologic function recovery were observed in both groups.Results:The incidence of adverse events in the observation group was 12.82%,significantly lower than the 33.33%in the control group,with a statistically significant difference(P<0.05).There was no statistically significant difference in restraint usage and ICU transfer rates between the two groups(P>0.05).The clinical symptom improvement time,hospital stay,and neurologic function recovery in the observation group were significantly better than those in the control group,with a statistically significant difference(P<0.05).Conclusion:Through the bundle management model,effective connections can be ensured in various aspects of treatment and rehabilitation for patients with autoimmune encephalitis,providing patients with comprehensive and multi-level nursing services and improving their overall satisfaction and treatment effectiveness.展开更多
Ship-bridge collisions happen from time to time globally, and the consequences are often catastrophic. Therefore, this paper pro-poses a new high-pressure water jet interference (HPWJI) method for bridge pier protecti...Ship-bridge collisions happen from time to time globally, and the consequences are often catastrophic. Therefore, this paper pro-poses a new high-pressure water jet interference (HPWJI) method for bridge pier protection against vessel collision. Unliketraditional methods that absorb energy by anti-collision devices to mitigate the impact force of ships on bridges, this methodmainly changes the direction of ship movement by lateral high-pressure water jet impact, so that the ship deviates from the bridgepiers and avoids collision. This paper takes China’s Shawan River as the background and simulates the navigation of a ship(weighing about 2000 t) in the HPWJI method in the ANSYS-FLUENT software. The simulation results show that the HPWJImethod has a significant impact on the direction of the ship’s movement, enabling the ship to deviate from the pier, which istheoretically feasible for preventing bridge-ship collisions. The faster the ship’s speed, the smaller the lateral displacement anddeflection angle of the ship during a certain displacement. When the ship speed is less than 7 m/s, the impact of water flow onthe ship’s trajectory is more significant. Finally, this paper constructs a model formula for the relationship between the lateraldisplacement and speed, and surge displacement of the selected ship. This formula can be used to predict the minimum safedistance of the ship at different speeds.展开更多
The scientific article discusses the principles of ecological landscaping of the classroom related to the creation and development of a safe educational environment.The functions of vertical landscaping of the classro...The scientific article discusses the principles of ecological landscaping of the classroom related to the creation and development of a safe educational environment.The functions of vertical landscaping of the classroom and the territo-ry,as well as the plants used in it,are defined.The ways of creating the principle of“tieredness”in ecological gardening are determined.The conformity of the measurements of landscaping inside the classroom with the norms of safety of landscaping according to SanPiN KR was determined and their results were presented.In our study,we took the green component of ecological safety as the basis of the educational environment.After all,the ecological landscaping of the educational room is an important and indispensable part of creating a favorable environment for the health of students and the development of complex:aesthetic,ecological culture.Greening plays a decisive role in maintaining a micro-climate favorable for health.When plants are properly placed according to safety standards in the classroom and on the territory,they provide shade,reduce dust,kill microorganisms causing infectious diseases and clean the air.Therefore,many species of native plants grown in Central Asia are used for the landscaping of educational buildings.展开更多
Hydraulic fracturing(HF)has achieved significant commercial success in unconventional oil and gas development.However,it has the potential to induce fault slip.This study investigates the physical mechanisms underlyin...Hydraulic fracturing(HF)has achieved significant commercial success in unconventional oil and gas development.However,it has the potential to induce fault slip.This study investigates the physical mechanisms underlying potential fault slip triggered by HF operations under varying geological and operational constraints.First,we elucidate the relationship between the critical stress state and the elastic modulus of the fault,and refine a formula for the maximum crustal stress difference on critically stressed faults,including stress concentration,friction,and dip.Second,we compare the role of injected fluid in permeable faults with that in impermeable faults,and demonstrate that fault slips can be triggered by a combination of friction decrease and pore pressure increase,even after ceasing injection.Specifically,we reveal that friction decline dominates induced fault slip on high permeable and hydraulically connected fault.Third,based on experimental results and theoretical analysis,we quantify the influence region of stress transfer under different conditions of well location and injection pressure.The results reveal that the elastic modulus of the fault controls the stress concentration on the fault plane.The dip of the fault and the stress concentration jointly determine the maximum crustal stress difference required for failure in critically stressed reverse faults.Thus,our study is more accurate in estimating the proximity of the in-situ stress to the critical state,compared with traditional methods.For critical reverse faults,the risk of induced slip is positively correlated with both injection pressure and friction of fault plane.When the injection pressure(PI)is 100 MPa and the friction(μ)is 0.8,the safe distance from injection point to critically stressed faults along the direction of maximum principal stress and maximum principal stress(dH and dv)should exceed 25 and 18 times as the hydraulic fracture halflength.When PI is 100 MPa andμis 0.6,dH and dv are 23 and 17 times as the hydraulic fracture halflength,respectively.When PI is 60 MPa andμis 0.6,dH and dv are 18 and 13 times as the hydraulic fracture half-length,respectively.The works enhance our understanding of HF-induced fault slip and potentially guide designs of the shale gas well location and trajectory for safer production.展开更多
The study aims to investigate uranium species in the sediments of the natural-technogenic system within a sludge storage facility in Russia.The relevance of this work is underscored by the need to assess the geochemic...The study aims to investigate uranium species in the sediments of the natural-technogenic system within a sludge storage facility in Russia.The relevance of this work is underscored by the need to assess the geochemical mobility of radionuclides,a critical factor for predicting their migration and environmental impact.The objective of the research was to determine the uranium species in both peat and sedimentary rock samples of the sludge storage facility and the adjacent area.Laboratory analyses included XRD,XRF analysis using synchrotron radiation,and scanning electron microscopy to study the composition and properties of minerals.The uranium species were further identified using a modified Tessier sequential extraction method.The results revealed that uranium predominantly occurs in a stable silicate-bound form(up to 80%)in sedimentary rocks,indicating minimal geochemical mobility.In contrast,in peat deposits,uranium is primarily associated with manganese and iron oxides(30–60%)as well as organic matter(5–40%),with the most mobile forms constituting less than 5%.The decrease in uranium concentration with distance from the facility was attributed to sorption onto organic matter and co-precipitation with mineral compounds,manganese and iron oxides,which serve as effective natural sorbents.The findings highlight the critical role of organic matter and metal oxides in limiting uranium migration,thus identifying them as key components in the formation of natural barriers for radionuclides.These results are crucial for assessing environmental risks associated with radioactive waste management and for developing strategies to minimize the ecological impact of sludge storages.展开更多
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support of the National Key Research and Development Plan(Grant No.2021YFB3302501)the financial support of the National Science Foundation of China(Grant No.12161076)the financial support of the Fundamental Research Funds for the Central Universities(Grant No.DUT24LAB129).
文摘As carrier aircraft sortie frequency and flight deck operational density increase,autonomous dispatch trajectory planning for carrier-based vehicles demands efficient,safe,and kinematically feasible solutions.This paper presents an Iterative Safe Dispatch Corridor(iSDC)framework,addressing the suboptimality of the traditional SDC method caused by static corridor construction and redundant obstacle exploration.First,a Kinodynamic-Informed-Bidirectional Rapidly-exploring Random Tree Star(KIBRRT^(*))algorithm is proposed for the front-end coarse planning.By integrating bidirectional tree expansion,goal-biased elliptical sampling,and artificial potential field guidance,it reduces unnecessary exploration near concave obstacles and generates kinematically admissible paths.Secondly,the traditional SDC is implemented in an iterative manner,and the obtained trajectory in the current iteration is fed into the next iteration for corridor generation,thus progressively improving the quality of withincorridor constraints.For tractors,a reverse-motion penalty function is incorporated into the back-end optimizer to prioritize forward driving,aligning with mechanical constraints and human operational preferences.Numerical validations on the data of Gerald R.Ford-class carrier demonstrate that the KIBRRT^(*)reduces average computational time by 75%and expansion nodes by 25%compared to conventional RRT^(*)algorithms.Meanwhile,the iSDC framework yields more time-efficient trajectories for both carrier aircraft and tractors,with the dispatch time reduced by 31.3%and tractor reverse motion proportion decreased by 23.4%relative to traditional SDC.The presented framework offers a scalable solution for autonomous dispatch in confined and safety-critical environment,and an illustrative animation is available at bilibili.com/video/BV1tZ7Zz6Eyz.Moreover,the framework can be easily extended to three-dimension scenarios,and thus applicable for trajectory planning of aerial and underwater vehicles.
文摘The Hainan FTP is a game changer,and those who seize the opportunities it offers early will be in an advantageous position As it provides a vital new model for China’s international trade and logistics,the Hainan Free Trade Port(FTP)stands out among similar opening-up initiatives.
基金National Key Research and Development Program of China(No.2023YFB4104204)National Natural Science Foundation of China(No.U23B2090).
文摘The utilization and storage of CO_(2) emissions from oil production and consumption in the upstream oil industry will contribute to sustainable development.CO_(2) flooding is the key technology for the upstream oil industry to transition to sustainable development.However,there is a significant challenge in achieving high recovery and storage efficiency in unconventional reservoirs,particularly in underde-veloped countries.Numerous studies have indicated that the limited sweep range caused by premature gas channeling of CO_(2) is a crucial bottleneck that hinders the enhancement of recovery,storage efficiency and safety.This review provides a comprehensive summary of the research and technical advancements regarding the front sweep characteristics of CO_(2) during migration.It particularly focuses on the char-acteristics,applicable stages,and research progress of different technologies used for regulating CO_(2) flooding sweep.Finally,based on the current application status and development trends,the review offers insights into the future research direction for these technologies.It is concluded that the front migration characteristics of CO_(2) play a crucial role in determining the macroscopic sweep range.The focus of future research lies in achieving cross-scale correlation and information coupling of CO_(2) migration processes.Currently,the influence weight of permeability,injection speed,pressure and other parameters on the characteristics of‘fingering-gas channeling’is still not well clear.There is an urgent need to establish prediction model and early warning mechanism that considers multi-parameters and cross-scale gas channeling degrees,in order to create effective strategies for prevention and control.There are currently three technologies available for sweep regulation:flow field intervention,mobility reduction,and gas channeling plugging.To expand the sweep effectively,it is important to systematically integrate these technologies based on their regulation characteristics and applicable stages.This can be achieved by constructing an intelligent synergistic hierarchical segmented regulation technology known as‘flow field intervention+mobility regulation+channel plugging chemically’.This work is expected to provide valuable insights for achieving conformance control of CO_(2)-EOR and safe storage of CO_(2).
基金supported by the National Natural Science Foundation of China(No.62203256)。
文摘Generating dynamically feasible trajectory for fixed-wing Unmanned Aerial Vehicles(UAVs)in dense obstacle environments remains computationally intractable.This paper proposes a Safe Flight Corridor constrained Sequential Convex Programming(SFC-SCP)to improve the computation efficiency and reliability of trajectory generation.SFC-SCP combines the front-end convex polyhedron SFC construction and back-end SCP-based trajectory optimization.A Sparse A^(*)Search(SAS)driven SFC construction method is designed to efficiently generate polyhedron SFC according to the geometric relation among obstacles and collision-free waypoints.Via transforming the nonconvex obstacle-avoidance constraints to linear inequality constraints,SFC can mitigate infeasibility of trajectory planning and reduce computation complexity.Then,SCP casts the nonlinear trajectory optimization subject to SFC into convex programming subproblems to decrease the problem complexity.In addition,a convex optimizer based on interior point method is customized,where the search direction is calculated via successive elimination to further improve efficiency.Simulation experiments on dense obstacle scenarios show that SFC-SCP can generate dynamically feasible safe trajectory rapidly.Comparative studies with state-of-the-art SCP-based methods demonstrate the efficiency and reliability merits of SFC-SCP.Besides,the customized convex optimizer outperforms off-the-shelf optimizers in terms of computation time.
基金jointly funded by the guangxi Science and Technology Base and Talent Project(AD23026104)the Key Research and Development Program Project in Guangxi(AB23026121)。
文摘Due to the influence of karst cave development and route selection,the location relationship between concealed karst cave and tunnel is more random.In order to explore the influence rule of karst cave location on the minimum safe thickness of water-proof rock mass,a simplified calculation model of water-proof rock mass thickness when the karst cave is located at any location around the tunnel is established,and the influence of multiple factors on the overall stability of water-proof rock mass is considered.Based on the cusp catastrophe theory,the analytical expressions for the safety thickness of waterproof rock mass are derived.Based on the finite difference principle,the analytical expressions of the safety thickness of water-proof rock mass are verified.In order to improve the application range of the analytical formula derived in this paper,the analytical formula is optimized based on the instability principle differences between the simplified calculation model and the elastic compressive bar.The research results show that the necessary condition solution is more applicable and much safer than the sufficient condition solution.Tectonic stress,rock beam length and karst cave water pressure are significantly positively correlated with the safe thickness of the waterproof rock mass.The calculated results of the semioptimized formula and the unoptimized formula are constant values,independent of the karst cave location.While the calculated results of the fully optimized formula are variable values,correlated with the karst cave location,the thickness of the waterproof rock mass gradually decreases as the karst cave location moves from the top of the tunnel to the bottom of the tunnel.The unoptimized formula does not consider the influence of the lateral force of the rock beam,and is not suitable for the working condition with large lateral force,the calculation results of the semi-optimized formula and the fully optimized formula are not very different and are biased to safety,so it can be given priority.
文摘Grasping is one of the most fundamental operations in modern robotics applications.While deep rein-forcement learning(DRL)has demonstrated strong potential in robotics,there is too much emphasis on maximizing the cumulative reward in executing tasks,and the potential safety risks are often ignored.In this paper,an optimization method based on safe reinforcement learning(Safe RL)is proposed to address the robotic grasping problem under safety constraints.Specifically,considering the obstacle avoidance constraints of the system,the grasping problem of the manipulator is modeled as a Constrained Markov Decision Process(CMDP).The Lagrange multiplier and a dynamic weighted mechanism are introduced into the Proximal Policy Optimization(PPO)framework,leading to the development of the dynamic weighted Lagrange PPO(DWL-PPO)algorithm.The behavior of violating safety constraints is punished while the policy is optimized in this proposed method.In addition,the orientation control of the end-effector is included in the reward function,and a compound reward function adapted to changes in pose is designed.Ultimately,the efficacy and advantages of the suggested method are proved by extensive training and testing in the Pybullet simulator.The results of grasping experiments reveal that the recommended approach provides superior safety and efficiency compared with other advanced RL methods and achieves a good trade-off between model learning and risk aversion.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT,Ministry of Science and ICT)[No.2022R1A2C1010596][NRF-2022R1A2C1010596].
文摘Since its introduction as a decentralized digital currency for peer-to-peer transactions,Bitcoin’s role in financial markets has undergone significant evolution.We employ bibliometric analysis to explore research trends in Bitcoin,identifying two primary perspectives in the recent financial economic literature:Bitcoin as a speculative asset and as a safe-haven asset.The speculative nature of Bitcoin is evident through its high volatility and frequent price jumps,largely influenced by rapid shifts in investor sentiment and attention,which create both risks and opportunities for traders.Conversely,Bitcoin exhibits characteristics of a safe-haven asset due to its asymmetric tail dependence and negative correlation within certain asset classes.
基金supported by Postdoctoral Fellowship Program of CPSF(Grant No.GZB20240816)China Postdoctoral Science Foundation(Grant No.2024M753474)+3 种基金National Natural Science Foundation of China(Grant No.72404267)National Social Science Fund(Grant No.23BGLI88)National Key Research and Development Program of China(Grant No.2017YFC0405805–04)Major program of the National Social Science Fund(Grant No.19ZDA084).
文摘Urbanization develops with the goal of establishing improved and more sustainable habitats for residents.Environmental and social performance must be simultaneously monitored to ascertain whether regions are progressing towards or deviating from the safe and just space(SJS)in urbanization.Despite relevant studies,the absence of indicators that bridge ecological preservation and human well-beings renders dual monitoring challenging.This study bridged the gap by exploring the interactions between urbanization,ecosystem services(ESs),and basic water,energy,and food(WEF)needs within the SJS framework across China and its provinces.By quantifying the minimum and actual demands for freshwater withdrawal,carbon emissions,phosphorus emissions,and land use,as well as the supply of ESs into unified biophysical indicators,we found that:(1)China can meet the basic WEF needs for all from 2000 to 2020,but only water and land provisioning ESs can operate within the SJS.Carbon emissions surpassed the sequestration capacity in 2010,while phosphorus purification ES has consistently been unsafe.(2)The SJS performance in terms of ecological and social fulfilment exhibited scale differences and undergone changes with urbanization.Overall,no province in China can consistently operate within all SJSs.(3)In the process of urbanization,improvements in ecological protection and production practices in most provinces expanded the size of SJS,but the continuous increase in total demand failed to steer regions toward safer spaces.Our framework emphasized the common but differentiated pathways that regions at varying stages of urbanization navigate to achieve safety and justice.It also provides an applicable solution for regions aiming to pursue urban growth while maintaining ecological conservation and social justice,ultimately achieving sustainable development.
文摘Hydropol a water-soluble,marine-safe,non-toxic polymer,is set to revolutionize the manufacture of hygiene products,suchas wet wipes and sanitary pads by making them dissolvable,fulyflushable and preventing them from forming fatbergs in sewers andreleasing harmful microplastics.This is thanks to the developmentof a revolutionary new dissolvable nonwoven material(flat,poroussheets that are made directly from separate filbres or from moltenplastic or plastic film)which uses Hydropol instead of conventionalplastics and helps prevent tonnes of plastic pollution from enteringthe environment.
文摘Objective:Nurses must follow safe injection practices to prevent healthcare-associated infections(HAIs).This study aimed to identify the risk factors for safe injection practice among nurses in general hospitals.Methods:This cross-sectional study included 215 nurses employed in Korean general hospitals.Data were collected from September 22 to October 9,2023.Multiple linear regression analysis was performed using SPSS Statistics 27.0.Results:The regression analysis revealed that a higher level of patient safety priority in the patient safety culture perception,increased knowledge of safe injection practices,and fewer working hours per week were associated with improved performance of safe injection practices among general hospital nurses.Conclusions:To enhance the performance of general hospital nurses in safe injection practice,it is necessary to establish a patient safety culture so that nurses recognize patient safety as a top priority.Additionally,an effective educational program is needed to increase the practical knowledge of safe injection practices,along with a supportive working environment that ensures appropriate working hours to prevent patient safety incidents.
文摘Investing in cryptocurrencies is progressively becoming a norm;however,these assets are excessively volatile and often decrease or increase in value instantly.Thus,rational investors holding cryptocurrencies for extended periods firmly search for assets that can diversify their risk,preferably with assets other than cryptocurrencies.In this study,we consider the two most studied cryptocurrencies with the highest capitalization and trading volume/value,namely Bitcoin and Ethereum.Specifically,we examine whether high-performing leading US tech stocks(Facebook,Amazon,Apple,Netflix,Google[FAANG])can provide any diversification benefits to cryptocurrency investors.To do so,we employ dynamic conditional correlation(DCC),asymmetric DCC,time-varying parameter vector autoregression-based connectedness measures,dynamic correlation-based hedge and safe-haven regression analyses,portfolio optimization and hedging strategies,time-and frequency-based wavelet coherence,and high-frequency 10-min intraday data from January 1,2018 to January 31,2023.We find that FAANG stocks can be considered(at least weak)safe havens for Bitcoin and Ethereum during the sample period.Our subperiod analyses reveal that the safehaven role of FAANG stocks,specifically for Bitcoin,has noticeably increased.While the safe-haven property of Facebook is the most promising,for Netflix it is blurred between a weak–safe-haven and a hedge.Our findings may help investors,policymakers,and academicians to invest in cryptocurrencies,formulate relevant investment guidelines,and extend the literature on cryptocurrencies,respectively.
文摘With the increasingly turbulent political situation and the outbreak of public health events without warning,it will not only affect people’s physical health,but also affect the global financial market,causing the market to fall into a huge crisis,thus leading to a continued decline in the worldwide economy.During periods of financial market turmoil,many investors fall into panic and urgently need a“haven”to protect their assets.With the rise of the digital economy,gold no longer seems to be the only safe-haven option.Bitcoin has gradually entered the investors’field of vision.Some investors believe that Bitcoin can become an emerging safe-haven asset that is as important as or surpasses gold.Based on an analysis of the safe-haven properties of Bitcoin and gold during major political and historical events and public health events,this article will clarify which of the two is more suitable as a reliable contemporary safe-haven asset and provide advice to investors.
文摘Objective:To explore the application effect of bundle management in the safe nursing of patients with autoimmune encephalitis.Methods:Seventy-five patients with autoimmune encephalitis who met the inclusion criteria in our hospital from January 2024 to June 2024 were randomly divided into two groups:an observation group of 39 patients and a control group of 36 patients.The control group received routine nursing care,while the observation group implemented a bundle management strategy based on routine nursing care.Safety nursing outcomes,clinical symptom improvement time,hospital stay,and neurologic function recovery were observed in both groups.Results:The incidence of adverse events in the observation group was 12.82%,significantly lower than the 33.33%in the control group,with a statistically significant difference(P<0.05).There was no statistically significant difference in restraint usage and ICU transfer rates between the two groups(P>0.05).The clinical symptom improvement time,hospital stay,and neurologic function recovery in the observation group were significantly better than those in the control group,with a statistically significant difference(P<0.05).Conclusion:Through the bundle management model,effective connections can be ensured in various aspects of treatment and rehabilitation for patients with autoimmune encephalitis,providing patients with comprehensive and multi-level nursing services and improving their overall satisfaction and treatment effectiveness.
基金supported by the National Natural Science Foundation of China (Grant No.11802347)Guangdong Basic and Applied Basic Research Foundation (Grant Nos.2018A030310334 and 2023A1515012482)Guangzhou Basic and Applied Basic Research Foundation (Grant No.2023A04J1618).
文摘Ship-bridge collisions happen from time to time globally, and the consequences are often catastrophic. Therefore, this paper pro-poses a new high-pressure water jet interference (HPWJI) method for bridge pier protection against vessel collision. Unliketraditional methods that absorb energy by anti-collision devices to mitigate the impact force of ships on bridges, this methodmainly changes the direction of ship movement by lateral high-pressure water jet impact, so that the ship deviates from the bridgepiers and avoids collision. This paper takes China’s Shawan River as the background and simulates the navigation of a ship(weighing about 2000 t) in the HPWJI method in the ANSYS-FLUENT software. The simulation results show that the HPWJImethod has a significant impact on the direction of the ship’s movement, enabling the ship to deviate from the pier, which istheoretically feasible for preventing bridge-ship collisions. The faster the ship’s speed, the smaller the lateral displacement anddeflection angle of the ship during a certain displacement. When the ship speed is less than 7 m/s, the impact of water flow onthe ship’s trajectory is more significant. Finally, this paper constructs a model formula for the relationship between the lateraldisplacement and speed, and surge displacement of the selected ship. This formula can be used to predict the minimum safedistance of the ship at different speeds.
文摘The scientific article discusses the principles of ecological landscaping of the classroom related to the creation and development of a safe educational environment.The functions of vertical landscaping of the classroom and the territo-ry,as well as the plants used in it,are defined.The ways of creating the principle of“tieredness”in ecological gardening are determined.The conformity of the measurements of landscaping inside the classroom with the norms of safety of landscaping according to SanPiN KR was determined and their results were presented.In our study,we took the green component of ecological safety as the basis of the educational environment.After all,the ecological landscaping of the educational room is an important and indispensable part of creating a favorable environment for the health of students and the development of complex:aesthetic,ecological culture.Greening plays a decisive role in maintaining a micro-climate favorable for health.When plants are properly placed according to safety standards in the classroom and on the territory,they provide shade,reduce dust,kill microorganisms causing infectious diseases and clean the air.Therefore,many species of native plants grown in Central Asia are used for the landscaping of educational buildings.
基金supported by the National Natural Science Foundation of China(No.:52274175)。
文摘Hydraulic fracturing(HF)has achieved significant commercial success in unconventional oil and gas development.However,it has the potential to induce fault slip.This study investigates the physical mechanisms underlying potential fault slip triggered by HF operations under varying geological and operational constraints.First,we elucidate the relationship between the critical stress state and the elastic modulus of the fault,and refine a formula for the maximum crustal stress difference on critically stressed faults,including stress concentration,friction,and dip.Second,we compare the role of injected fluid in permeable faults with that in impermeable faults,and demonstrate that fault slips can be triggered by a combination of friction decrease and pore pressure increase,even after ceasing injection.Specifically,we reveal that friction decline dominates induced fault slip on high permeable and hydraulically connected fault.Third,based on experimental results and theoretical analysis,we quantify the influence region of stress transfer under different conditions of well location and injection pressure.The results reveal that the elastic modulus of the fault controls the stress concentration on the fault plane.The dip of the fault and the stress concentration jointly determine the maximum crustal stress difference required for failure in critically stressed reverse faults.Thus,our study is more accurate in estimating the proximity of the in-situ stress to the critical state,compared with traditional methods.For critical reverse faults,the risk of induced slip is positively correlated with both injection pressure and friction of fault plane.When the injection pressure(PI)is 100 MPa and the friction(μ)is 0.8,the safe distance from injection point to critically stressed faults along the direction of maximum principal stress and maximum principal stress(dH and dv)should exceed 25 and 18 times as the hydraulic fracture halflength.When PI is 100 MPa andμis 0.6,dH and dv are 23 and 17 times as the hydraulic fracture halflength,respectively.When PI is 60 MPa andμis 0.6,dH and dv are 18 and 13 times as the hydraulic fracture half-length,respectively.The works enhance our understanding of HF-induced fault slip and potentially guide designs of the shale gas well location and trajectory for safer production.
基金supported by the Russian Science Foundation grant number 23-27-00362,https://rscf.ru/en/project/23-27-00362/.
文摘The study aims to investigate uranium species in the sediments of the natural-technogenic system within a sludge storage facility in Russia.The relevance of this work is underscored by the need to assess the geochemical mobility of radionuclides,a critical factor for predicting their migration and environmental impact.The objective of the research was to determine the uranium species in both peat and sedimentary rock samples of the sludge storage facility and the adjacent area.Laboratory analyses included XRD,XRF analysis using synchrotron radiation,and scanning electron microscopy to study the composition and properties of minerals.The uranium species were further identified using a modified Tessier sequential extraction method.The results revealed that uranium predominantly occurs in a stable silicate-bound form(up to 80%)in sedimentary rocks,indicating minimal geochemical mobility.In contrast,in peat deposits,uranium is primarily associated with manganese and iron oxides(30–60%)as well as organic matter(5–40%),with the most mobile forms constituting less than 5%.The decrease in uranium concentration with distance from the facility was attributed to sorption onto organic matter and co-precipitation with mineral compounds,manganese and iron oxides,which serve as effective natural sorbents.The findings highlight the critical role of organic matter and metal oxides in limiting uranium migration,thus identifying them as key components in the formation of natural barriers for radionuclides.These results are crucial for assessing environmental risks associated with radioactive waste management and for developing strategies to minimize the ecological impact of sludge storages.
