The development of bare patches typically signifies a process of ecosystem degradation.Within the protection system of Shapotou section of the Baotou-Lanzhou railway,the extensive emergence of bare sand patches poses ...The development of bare patches typically signifies a process of ecosystem degradation.Within the protection system of Shapotou section of the Baotou-Lanzhou railway,the extensive emergence of bare sand patches poses a threat to both stability and sustainability.However,there is limited knowledge regarding the morphology,dynamic changes,and ecological responses associated with these sand patches.Therefore,we analyzed the formation and development process of sand patches within the protection system and its effects on herbaceous vegetation growth and soil nutrients through field observation,survey,and indoor analysis methods.The results showed that sand patch development can be divided into three stages,i.e.,formation,expansion,and stabilization,which correspond to the initial,actively developing,and semi-fixed sand patches,respectively.The average dimensions of all sand patch erosional areas were found to be 7.72 m in length,3.91 m in width,and 0.32 m in depth.The actively developing sand patches were the largest,and the initial sand patches were the smallest.Throughout the stage of formation and expansion,the herbaceous community composition changed,and the plant density decreased by more than 50.95%.Moreover,the coverage and height of herbaceous plants decreased in the erosional area and slightly increased in the depositional lobe;and the fine particles and nutrients of soils in the erosional area and depositional lobe showed a decreasing trend.In the stabilization phases of sand patches,the area from the inlet to the bottom of sand patches becomes initially covered with crusts.Vegetation and 0-2 cm surface soil condition improved in the erosional area,but this improvement was not yet evident in the depositional lobe.Factors such as disturbance,climate change,and surface resistance to erosion exert notable influences on the formation and dynamics of sand patches.The results can provide evidence for the future treatment of sand patches and the management of the protection system of Shapotou section of the Baotou-Lanzhou railway.展开更多
Thyristors have longer lifetimes,higher reliability,and very high voltage and current ratings and they require less maintenance than other high-power semiconductor devices.As a result,they are particularly suitable fo...Thyristors have longer lifetimes,higher reliability,and very high voltage and current ratings and they require less maintenance than other high-power semiconductor devices.As a result,they are particularly suitable for quench protection systems(QPSs),which protect the superconducting magnets in large fusion devices from damage.In this paper,we propose a design for a 100 k A/10 k V thyristor stack supported by both theoretical and simulation-based analyses as well as experimental verification.Due to the ultrahigh electrical performance requirements imposed on the QPS by the Comprehensive Research Facility for Fusion Technology(CRAFT),three main issues must be considered:the voltage-balancing problem caused by multiple thyristors in a series structure,the increased junction temperature problem caused by extremely high currents,and the reverse recovery phenomenon that arises from the thyristor’s physical structure.Hence,a series of detailed theoretical analyses,simulations,and experiments,including a thyristor junction temperature prediction method and reverse recovery process modeling,were carried out to optimize the design.Finally,the reliability and stability of the thyristor stack were verified by a series of prototype experiments.The results confirmed the correctness and accuracy of the proposed thyristor stack design method and also indicated that the proposed thyristor stack can meet the application conditions of a 100 k A QPS in the CRAFT project.展开更多
Assessment of railway wheel slide protection(WSP) systems involves the execution of complex experimental activities that are quite expensive and time-consuming, since they involve the physical reproduction of degraded...Assessment of railway wheel slide protection(WSP) systems involves the execution of complex experimental activities that are quite expensive and time-consuming, since they involve the physical reproduction of degraded adhesion conditions on a real railway line. WSP is devoted to regulating applied braking forces to avoid excessive wheel sliding in case of degraded adhesion conditions between wheel and rail. WSP must be also compliant to safety specifications related to assured braking performances and consumed air. Hardware in the loop(HIL) testing offers an affordable and sustainable way to accelerate these activities optimizing cost, duration and safety of experimental activities performed online. HIL test rigs are subjected to continuous updates, customization and natural ageing of their components. This work investigates the criteria that can be adopted to assure a continuous monitoring and validation of a real WSP test rig, the Italian test rig of Firenze Osmannoro.展开更多
Rice is one of the main staple food crops in the world, but it may suffer serious water stress during growth period. Water stress during grain filling results in decreased grain yeild, but its mechanism generating and...Rice is one of the main staple food crops in the world, but it may suffer serious water stress during growth period. Water stress during grain filling results in decreased grain yeild, but its mechanism generating and scavenging the active oxygen is unclear under continuance of the water stress. The experiment was carried out in growth chamber to investigate the effects of water stress on the production of superoxide free radical (O2), hydrogen peroxide (H202), malondialdehyde (MDA), reduced glutathione (GSH), ascorbic acid (AsA), and antioxidative enzyme activities in three rice hybrids with differing drought resistant under both normal and drought conditions during grain-filling stage. The results showed that water stress aggravated the membrane lipid peroxidation in rice leaves, which was more severe in less drought resistant hybrids than that in more tolerant ones. Also O2' and H2O2 accumulated more rapidly in less drought resistant hybrids than that in more tolerant ones. During water stress, decreases of GSH, AsA, chlorophyll, and relative water contents in more drought resistant hybrids were obvious less than those in less tolerant ones. Activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in/eaves increased obviously in 0-14 d after heading and subsequently decreased rapidly, and those in more drought resistant hybrids were more than those in less tolerant ones. The results showed that changes of O2, H2O2, MDA, GSH, and AsA contents and antioxidative enzyme activities correlated significantly to drought resistance of rice hybrids, and more drought resistant hybrids possessed high ant oxidation capacity.展开更多
The three-dimensional Navier Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow ...The three-dimensional Navier Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow conditions. The numerical method is validated by the relevant experiment. The flow field parameters, aerodynamic forces, and surface heat flux distributions for attack angles of 0°, 2°, 5°, 7°, and 10° are obtained. The detailed numerical results show that the cruise attack angle has a great influence on the flow field parameters, aerodynamic force, and surface heat flux distribution of the supersonic vehicle nose-tip with an opposing jet thermal protection system. When the attack angle reaches 10°, the heat flux on the windward generatrix is close to the maximal heat flux on the wall surface of the nose-tip without thermal protection system, thus the thermal protection has failed.展开更多
The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of...The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of hypersonic vehicles.Triply periodic minimal surface(TPMS)is especially suitable for the structural design of the internal cavity of regenerative cooling structures owing to its excellent structural characteristics.In this study,test pieces were manufactured using Ti6Al4V lightweight material.We designed three types of porous test pieces,and the interior was filled with a TPMS lattice(Gyroid,Primitive,I-WP)with a porosity of 30%.All porous test pieces were manufactured via selective laser melting technology.A combination of experiments and finite element simulations were performed to study the selection of the internal cavity structure of the regenerative cooling thermal protection system.Hence,the relationship between the geometry and mechanical properties of a unit cell is established,and the deformation mechanism of the porous unit cell is clarified.Among the three types of porous test pieces,the weight of the test piece filled with the Gyroid unit cell was reduced by 8.21%,the average tensile strength was reduced by 17.7%compared to the solid test piece,while the average tensile strength of the Primitive and I-WP porous test pieces were decreased by 30.5%and 33.3%,respectively.Compared with the other two types of unit cells,Gyroid exhibited better mechanical conductivity characteristics.Its deformation process was characterised by stretching,shearing,and twisting,while the Primitive and I-WP unit cells underwent tensile deformation and tensile and shear deformation,respectively.The finite element predictions in the study agree well with the experimental results.The results can provide a basis for the design of regenerative cooling thermal protection system.展开更多
The digital reactor protection system(RPS)is one of the most important digital instrumentation and control(I&C)systems utilized in nuclear power plants(NPPs).It ensures a safe reactor trip when the safety-related ...The digital reactor protection system(RPS)is one of the most important digital instrumentation and control(I&C)systems utilized in nuclear power plants(NPPs).It ensures a safe reactor trip when the safety-related parameters violate the operational limits and conditions of the reactor.Achieving high reliability and availability of digital RPS is essential to maintaining a high degree of reactor safety and cost savings.The main objective of this study is to develop a general methodology for improving the reliability of the RPS in NPP,based on a Bayesian Belief Network(BBN)model.The structure of BBN models is based on the incorporation of failure probability and downtime of the RPS I&C components.Various architectures with dual-state nodes for the I&C components were developed for reliability-sensitive analysis and availability optimization of the RPS and to demonstrate the effect of I&C components on the failure of the entire system.A reliability framework clarified as a reliability block diagram transformed into a BBN representation was constructed for each architecture to identify which one will fit the required reliability.The results showed that the highest availability obtained using the proposed method was 0.9999998.There are 120 experiments using two common component importance measures that are applied to define the impact of I&C modules,which revealed that some modules are more risky than others and have a larger effect on the failure of the digital RPS.展开更多
Ultra-high temperature ceramics(UHTCs)are a family of borides,carbides and nitrides of transition elements such as hafnium,zirconium,tantalum and niobium.They exhibit the highest known melting points,good mechanical s...Ultra-high temperature ceramics(UHTCs)are a family of borides,carbides and nitrides of transition elements such as hafnium,zirconium,tantalum and niobium.They exhibit the highest known melting points,good mechanical strength,good chemical and thermal stability under certain conditions.In last decade,researchers dedicated to characterize porous UHTCs aiming to develop novel thermal insulating materials that could withstand temperatures over 2000℃.In this article,the preparation and characteristics of porous UHTCs were reviewed.Dry processing,colloidal processing and solution processing routes have been used to prepare porous UHTCs with porosities ranging from 5%to 97%and pore sizes ranging from hundreds of nanometers to hundreds of micrometers.The obtained porous UHTCs are chemically and dimensionally stable at temperatures up to 2000℃ during static state high-temperature thermal aging.展开更多
In this paper, the composition of HT-7 LHCD system along with its protection systems is introduced. It is very important for us to run the LHCD system safely and efficiently.
<strong>Background: </strong>Numerous studies have demonstrated increasing evidence for cataractogenesis at lower levels of ionizing radiation than previously believed, with some suggesting possible absenc...<strong>Background: </strong>Numerous studies have demonstrated increasing evidence for cataractogenesis at lower levels of ionizing radiation than previously believed, with some suggesting possible absence of a threshold. Genetic differences between individuals also result in increased susceptibility in some operators, who might not be aware. European occupational exposure limits have been reduced and operators are seeking protective measures. <strong>Objective: </strong>To evaluate the protective effect of a face-shield equipped suspended protection system (Zero-Gravity<span style="white-space:nowrap;"><sup><span style="white-space:nowrap;">®</span></sup></span>, TIDI Products, Neenah, WI) along with adherence to safety practices against radiation dose to the eye lens for an interventional radiologist performing a wide variety of procedures. <strong>Materials and Methods:</strong> In this institutional review board-approved single-institution study, one interventional radiologist wore a highly sensitive personnel monitoring dosimeter badge on the cap near the left eye while performing 299 procedures (3690 fluoroscopy minutes) over 18 consecutive months while utilizing the suspended protection system along with adherence to other generally recommended safety practices and movement away from the field during angiographic power injections. Dosimetry reports and procedural information were retrospectively reviewed. <strong>Results: </strong>Total lens dose equivalent to the left eye over 18 months was 0.11 mSv (annualized dose = 0.073 mSv, or 7.3 mRem). The patient-dose-area product standardized dose of 0.00576 <span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">μ</span></span></span>Sv/Gy<span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span>cm<sup>2</sup> is well below reports of conventional lead aprons, shields, and protective eyewear. <strong>Conclusion: </strong>Eye exposures were kept to near-background levels using the materials and methods of this study while performing a wide variety of complex procedures from all positions around the patient.展开更多
Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheatin...Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheating, a data acquisition and over-current protection system based on the PXI(PCI e Xtensions for Instrumentation) platform has been developed. The system consists of a current sensor, data acquisition module and over-current protection module. In the data acquisition module,the acquired data of one shot will be transferred in isolation and saved in a data-storage server in a txt file. It can also be recalled using NBWave for future analysis. The over-current protection module contains two modes: remote and local. This gives it the function of setting a threshold voltage remotely and locally, and the forbidden time of over-current protection also can be set by a host PC in remote mode. Experimental results demonstrate that the data acquisition and overcurrent protection system has the advantages of setting forbidden time and isolation transmission.展开更多
China’s trademark business hasmade much progress since thecountry began its reform and open-uppolicy. In 1979 there were only 32,589registered trademarks, of which 5,130were foreign ones. With the establishmentand im...China’s trademark business hasmade much progress since thecountry began its reform and open-uppolicy. In 1979 there were only 32,589registered trademarks, of which 5,130were foreign ones. With the establishmentand improvement of the trademarkprotection system, the valid registeredtrademarks had reached 465,865 by theend of 1994, and 70,216 of them were for70 countries and regions. Such speed israre in the world. The features of the country’strademark protection system are asfollows: 1. Definite legal regulations andclear government展开更多
This session of the Forum has the theme, “The Chinese Dream: New Progress in the Cause of Human Rights in China.” This theme concentrates on such important subtopics as “The Chinese Dream and Human Rights” ,
In wide area backup protection of electric power systems, the prerequisite of protection device's accurate, fast and reliable performance is its corresponding fault type and fault location can be discriminated qui...In wide area backup protection of electric power systems, the prerequisite of protection device's accurate, fast and reliable performance is its corresponding fault type and fault location can be discriminated quickly and defined exactly. In our study, global information will be introduced into the backup protection system. By analyzing and computing real-time PMU measurements, basing on cluster analysis theory, we are using mainly hierarchical cluster analysis to search after the statistical laws of electrical quantities' marked changes. Then we carry out fast and exact detection of fault components and fault sections, and finally accomplish fault isolation. The facts show that the fault detection of fault component (fault section) can be performed successfully by hierarchical cluster analysis and calculation. The results of hierarchical cluster analysis are accurate and reliable, and the dendrograms of hierarchical cluster analysis are in intuition.展开更多
Purpose: This clinical study compares conventional lead aprons and ancillary shields to a functionally weightless personal overhead-supported system with expanded coverage. Materials and Methods: Primary operators per...Purpose: This clinical study compares conventional lead aprons and ancillary shields to a functionally weightless personal overhead-supported system with expanded coverage. Materials and Methods: Primary operators performed procedures (N = 126, fluoroscopy minutes = 1209) using one of 2 methods of radiation protection and wearing dosimeters on multiple body locations. Method “LAS” (Lead-Apron+Shields): lead skirt, vest, thyroid shield, with 100% use of under-table shield, side shield, and mobile suspended lead-acrylic shield. Method “Zgrav”: ZeroGravity system (CFI Medical Solutions) with variable use of shielding. The studied early model moving with the operator had a curved lead-acrylic head shield (0.5 mm Pb) and expansive lead apron (0.5 - 1.0 mm Pb) that covered leg to distal calf and proximal arm to elbow, and a drape that permitted sterile entry and exit. Study was institutional review board approved and HIPPA-compliant. Results: Measured with a sensitive electronic dosimeter, eye exposures were 99% (P 0.001) reduced for Zgrav with upgraded face shield vs. LAS, regardless of use or non-use of suspended shield with Zgrav. With optically stimulated luminescence (OSL) dosimeters, operator exposures, standardized to minutes of fluoroscopy and Fluoroscopic Patient Dose Area Product, were reduced by 87% - 100% for eye & head, neck, humerus, and tibia (Zgrav vs. LAS). Overall eye & head exposure reduction for entire study was 94%. Non-equivalence of torso exposures was not demonstrated. A brief user survey showed ergonomic advantages of Zgrav. Conclusion: Compared to conventional lead aprons with shields, the suspended system provided superior operator protection during interventional fluoroscopy, allowing operators to perform procedures without potentially obstructive shields.展开更多
This paper examines the use of corrosion inhibitors in order to protect the reinforcement of concrete. For this purpose mortar specimens were constructed with or without corrosion inhibitors and were partially immerse...This paper examines the use of corrosion inhibitors in order to protect the reinforcement of concrete. For this purpose mortar specimens were constructed with or without corrosion inhibitors and were partially immersed in sodium chloride. Corrosion inhibitors were used as admixture into concrete and were sprayed on the external surface of mortar specimens. In all mortar specimens, electric junction between reinforcements was achieved. The methods that were used for the evaluation of the reinforcement corrosion in concrete, included half-cell potential measurements, polarization curves of reinforced rebars and mass loss of the reinforcement. Finally, the durability of concrete after the use of corrosion inhibitors was also examined.展开更多
In order to study the dynamic behaviors of the thermal protection system(TPS)and dynamic strength of the strain-isolation-pad(SIP),a two degree-of-freedom dynamic theoretical model is presented under the acoustic exci...In order to study the dynamic behaviors of the thermal protection system(TPS)and dynamic strength of the strain-isolation-pad(SIP),a two degree-of-freedom dynamic theoretical model is presented under the acoustic excitation and base excitation. The tile and SIP are both considered as the elastic body and simplified as a mass point,a linear spring and a damping element. The theoretical solutions are derived,and the reasonability of theoretical model is verified by comparing the theoretical results with the numerical results. Finally,the influences on the dynamic responses of TPS by the structural damping coefficient of TPS,elasticity modulus and thickness of SIP are analyzed.The results show that the material with higher damping,and SIP with thicker size and lower elastic modulus should be considered to reduce the dynamic responses and intensify the security of TPS. The researches provide a theoretical reference for studying the dynamic behaviors of TPS and the dynamic strength of SIP. Besides,the dynamic theoretical model can be used as a quick analysis tool for analyzing the dynamic responses of TPS during the initial design phase.展开更多
The issue of marine ecology is an institutional one.China’s marine ecological protection system has gone through a process of development from scratch to existence and from less to more.However,there are still many p...The issue of marine ecology is an institutional one.China’s marine ecological protection system has gone through a process of development from scratch to existence and from less to more.However,there are still many problems to be solved,such as whether a variety of complex systems can form a joint force of governance,and whether the rear system failures,deficiencies,and conflicts.Therefore,this paper reviews the evolution logic of China’s marine ecological protection system,explores the complementary space of the existing system from the perspective of institutional complementarity,and analyzes the path of institutional reform of supplement,amendment,and coordination,to promote the effective transition of marine ecological protection system emphasizing quality over quantity.The evolution of China’s marine ecological protection system can be divided into three stages:initial establishment,steady progression,and gradual transformation,showing a trend characterized by a changing governance mode from land-sea division to land-sea integration,a changing supervision mode from government only to multi-institution coordination,a changing safeguard mode from standard norms to the legal system.The internal motivation of promoting the evolution of the marine ecological protection system is the link age between the long-overdue institutional derived demand and supply,and between institutional cost constraints and institutional income drivers.Marine ecological protection is a complex and systematic project across regions and departments,and the link age between different ecological protection systems is crucial.Based on the theory of institutional complementarity,this study finds that China’s marine ecological protection system has great complementarity needs in three aspects:protection subject,protection means,and protection process.Among them,the problem of a single unitary protection subject is mainly caused by the lack of system,the low efficiency of protection means is mainly affected by the lack of system adaptability,and the separation of protection process mainly reflects the contradiction of system incongruity and mismatch.Based on this,the supplement of China’s marine ecological protection system should focus on the government’s responsibilities and the cultivation of multiple subjects.The revision of the system should focus on the further improvement of non-governmental mechanisms such as market incentives and information disclosure.The coordination of the system should be based on the whole process from pre regulation preparations to post-regulation review,in order to promote the effective connection and cooperation of policy tools.展开更多
The physical protection system of the body consists of the protective organs for vulnerable body parts-functions and the protective countermeasures against invaders (pathogens), but to survive, the body also requires ...The physical protection system of the body consists of the protective organs for vulnerable body parts-functions and the protective countermeasures against invaders (pathogens), but to survive, the body also requires the protective social groups for vulnerable social members-functions and the protective instinctive mental countermeasures against adversities such as hardship, danger, and unfamiliarity-uncertainty. As a result, this paper proposes that the mental protection system of the body consists of the social brain to set up the protective social groups for vulnerable social members-functions and the mental immune system to produce the protective mental countermeasures against adversities. This paper proposes that from the social brain, the protective social groups include alliance group for vulnerable individuals, kinship-friendship group for vulnerable children, interdependent specialists group for vulnerable pregnant females, territorial group for social boundary, connective group for social connection, and competitive group for social competition. From the mental immune system, the mental protective countermeasures include comforter against hardship, hyperactivity against danger, phobia against unfamiliarity-uncertainty, and rationality against unfamiliarity-uncertainty. The overactive mental immune system causes mental allergies and auto immune diseases as personality-mental disorders against ubiquitous harmful and harmless perceived adversities, correlating to physical allergies and auto immune diseases against ubiquitous harmful and harmless detected invaders. The mental protection system also produces personality traits, social moralities, social organizations, social systems, religions, and cultures as described in this paper. The mental protective system is the source of protective behaviors.展开更多
Because the leakage protection circuit in traction motor of coal mining machine is impacted by frequency converter devices,malfunctions appear frequently.This paper makes an in-depth analysis,proposes a solution of us...Because the leakage protection circuit in traction motor of coal mining machine is impacted by frequency converter devices,malfunctions appear frequently.This paper makes an in-depth analysis,proposes a solution of using the subtraction circuit to offset interference signals and conducts a simulation analysis.The above scheme,which is simple and easily realized,can improve the reliability of leakage protection device in traction motor.展开更多
基金supported by the Key Research and Development Program of Ningxia Hui Autonomous Region,China(2022BEG02003)the Excellent Member of Youth Innovation Promotion Association,Chinese Academy of Sciences(Y202085)the Youth Innovation Promotion Association,Chinese Academy of Sciences(2023448).
文摘The development of bare patches typically signifies a process of ecosystem degradation.Within the protection system of Shapotou section of the Baotou-Lanzhou railway,the extensive emergence of bare sand patches poses a threat to both stability and sustainability.However,there is limited knowledge regarding the morphology,dynamic changes,and ecological responses associated with these sand patches.Therefore,we analyzed the formation and development process of sand patches within the protection system and its effects on herbaceous vegetation growth and soil nutrients through field observation,survey,and indoor analysis methods.The results showed that sand patch development can be divided into three stages,i.e.,formation,expansion,and stabilization,which correspond to the initial,actively developing,and semi-fixed sand patches,respectively.The average dimensions of all sand patch erosional areas were found to be 7.72 m in length,3.91 m in width,and 0.32 m in depth.The actively developing sand patches were the largest,and the initial sand patches were the smallest.Throughout the stage of formation and expansion,the herbaceous community composition changed,and the plant density decreased by more than 50.95%.Moreover,the coverage and height of herbaceous plants decreased in the erosional area and slightly increased in the depositional lobe;and the fine particles and nutrients of soils in the erosional area and depositional lobe showed a decreasing trend.In the stabilization phases of sand patches,the area from the inlet to the bottom of sand patches becomes initially covered with crusts.Vegetation and 0-2 cm surface soil condition improved in the erosional area,but this improvement was not yet evident in the depositional lobe.Factors such as disturbance,climate change,and surface resistance to erosion exert notable influences on the formation and dynamics of sand patches.The results can provide evidence for the future treatment of sand patches and the management of the protection system of Shapotou section of the Baotou-Lanzhou railway.
基金supported by National Key Research and Development Program of China(Nos.2017YFE0300504 and 2017YFE0300500)the Comprehensive Research Facility for the Fusion Technology Program of China(No.2018000052-73-01-001228)。
文摘Thyristors have longer lifetimes,higher reliability,and very high voltage and current ratings and they require less maintenance than other high-power semiconductor devices.As a result,they are particularly suitable for quench protection systems(QPSs),which protect the superconducting magnets in large fusion devices from damage.In this paper,we propose a design for a 100 k A/10 k V thyristor stack supported by both theoretical and simulation-based analyses as well as experimental verification.Due to the ultrahigh electrical performance requirements imposed on the QPS by the Comprehensive Research Facility for Fusion Technology(CRAFT),three main issues must be considered:the voltage-balancing problem caused by multiple thyristors in a series structure,the increased junction temperature problem caused by extremely high currents,and the reverse recovery phenomenon that arises from the thyristor’s physical structure.Hence,a series of detailed theoretical analyses,simulations,and experiments,including a thyristor junction temperature prediction method and reverse recovery process modeling,were carried out to optimize the design.Finally,the reliability and stability of the thyristor stack were verified by a series of prototype experiments.The results confirmed the correctness and accuracy of the proposed thyristor stack design method and also indicated that the proposed thyristor stack can meet the application conditions of a 100 k A QPS in the CRAFT project.
文摘Assessment of railway wheel slide protection(WSP) systems involves the execution of complex experimental activities that are quite expensive and time-consuming, since they involve the physical reproduction of degraded adhesion conditions on a real railway line. WSP is devoted to regulating applied braking forces to avoid excessive wheel sliding in case of degraded adhesion conditions between wheel and rail. WSP must be also compliant to safety specifications related to assured braking performances and consumed air. Hardware in the loop(HIL) testing offers an affordable and sustainable way to accelerate these activities optimizing cost, duration and safety of experimental activities performed online. HIL test rigs are subjected to continuous updates, customization and natural ageing of their components. This work investigates the criteria that can be adopted to assure a continuous monitoring and validation of a real WSP test rig, the Italian test rig of Firenze Osmannoro.
基金supported by the National 863 Program of China (2002AA2Z4011)the Foundation for Personnel of Henan University of Science and Technology China.
文摘Rice is one of the main staple food crops in the world, but it may suffer serious water stress during growth period. Water stress during grain filling results in decreased grain yeild, but its mechanism generating and scavenging the active oxygen is unclear under continuance of the water stress. The experiment was carried out in growth chamber to investigate the effects of water stress on the production of superoxide free radical (O2), hydrogen peroxide (H202), malondialdehyde (MDA), reduced glutathione (GSH), ascorbic acid (AsA), and antioxidative enzyme activities in three rice hybrids with differing drought resistant under both normal and drought conditions during grain-filling stage. The results showed that water stress aggravated the membrane lipid peroxidation in rice leaves, which was more severe in less drought resistant hybrids than that in more tolerant ones. Also O2' and H2O2 accumulated more rapidly in less drought resistant hybrids than that in more tolerant ones. During water stress, decreases of GSH, AsA, chlorophyll, and relative water contents in more drought resistant hybrids were obvious less than those in less tolerant ones. Activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) in/eaves increased obviously in 0-14 d after heading and subsequently decreased rapidly, and those in more drought resistant hybrids were more than those in less tolerant ones. The results showed that changes of O2, H2O2, MDA, GSH, and AsA contents and antioxidative enzyme activities correlated significantly to drought resistance of rice hybrids, and more drought resistant hybrids possessed high ant oxidation capacity.
基金Project supported by the National Natural Science Foundation of China (Grant No. 90916018)the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 200899980006)the Natural Science Foundation of Hunan Province,China(Grant No. 09JJ3109)
文摘The three-dimensional Navier Stokes equation and the k-ε viscous model are used to simulate the attack angle characteristics of a hemisphere nose-tip with an opposing jet thermal protection system in supersonic flow conditions. The numerical method is validated by the relevant experiment. The flow field parameters, aerodynamic forces, and surface heat flux distributions for attack angles of 0°, 2°, 5°, 7°, and 10° are obtained. The detailed numerical results show that the cruise attack angle has a great influence on the flow field parameters, aerodynamic force, and surface heat flux distribution of the supersonic vehicle nose-tip with an opposing jet thermal protection system. When the attack angle reaches 10°, the heat flux on the windward generatrix is close to the maximal heat flux on the wall surface of the nose-tip without thermal protection system, thus the thermal protection has failed.
基金support from the National Natural Science Foundation of China(NSFC,Project Nos.91860136 and 51801231)the Key R&D Plan of Guangdong Province(Grant No.2018B090905001)the Key Science and Technology project of Shaanxi Province(Grant No.2018zdzx01-04-01).
文摘The new regenerative cooling thermal protection system exhibits the multifunctional characteristics of load-carrying and heat exchange cooling,which are fundamental for the lightweight design and thermal protection of hypersonic vehicles.Triply periodic minimal surface(TPMS)is especially suitable for the structural design of the internal cavity of regenerative cooling structures owing to its excellent structural characteristics.In this study,test pieces were manufactured using Ti6Al4V lightweight material.We designed three types of porous test pieces,and the interior was filled with a TPMS lattice(Gyroid,Primitive,I-WP)with a porosity of 30%.All porous test pieces were manufactured via selective laser melting technology.A combination of experiments and finite element simulations were performed to study the selection of the internal cavity structure of the regenerative cooling thermal protection system.Hence,the relationship between the geometry and mechanical properties of a unit cell is established,and the deformation mechanism of the porous unit cell is clarified.Among the three types of porous test pieces,the weight of the test piece filled with the Gyroid unit cell was reduced by 8.21%,the average tensile strength was reduced by 17.7%compared to the solid test piece,while the average tensile strength of the Primitive and I-WP porous test pieces were decreased by 30.5%and 33.3%,respectively.Compared with the other two types of unit cells,Gyroid exhibited better mechanical conductivity characteristics.Its deformation process was characterised by stretching,shearing,and twisting,while the Primitive and I-WP unit cells underwent tensile deformation and tensile and shear deformation,respectively.The finite element predictions in the study agree well with the experimental results.The results can provide a basis for the design of regenerative cooling thermal protection system.
文摘The digital reactor protection system(RPS)is one of the most important digital instrumentation and control(I&C)systems utilized in nuclear power plants(NPPs).It ensures a safe reactor trip when the safety-related parameters violate the operational limits and conditions of the reactor.Achieving high reliability and availability of digital RPS is essential to maintaining a high degree of reactor safety and cost savings.The main objective of this study is to develop a general methodology for improving the reliability of the RPS in NPP,based on a Bayesian Belief Network(BBN)model.The structure of BBN models is based on the incorporation of failure probability and downtime of the RPS I&C components.Various architectures with dual-state nodes for the I&C components were developed for reliability-sensitive analysis and availability optimization of the RPS and to demonstrate the effect of I&C components on the failure of the entire system.A reliability framework clarified as a reliability block diagram transformed into a BBN representation was constructed for each architecture to identify which one will fit the required reliability.The results showed that the highest availability obtained using the proposed method was 0.9999998.There are 120 experiments using two common component importance measures that are applied to define the impact of I&C modules,which revealed that some modules are more risky than others and have a larger effect on the failure of the digital RPS.
文摘Ultra-high temperature ceramics(UHTCs)are a family of borides,carbides and nitrides of transition elements such as hafnium,zirconium,tantalum and niobium.They exhibit the highest known melting points,good mechanical strength,good chemical and thermal stability under certain conditions.In last decade,researchers dedicated to characterize porous UHTCs aiming to develop novel thermal insulating materials that could withstand temperatures over 2000℃.In this article,the preparation and characteristics of porous UHTCs were reviewed.Dry processing,colloidal processing and solution processing routes have been used to prepare porous UHTCs with porosities ranging from 5%to 97%and pore sizes ranging from hundreds of nanometers to hundreds of micrometers.The obtained porous UHTCs are chemically and dimensionally stable at temperatures up to 2000℃ during static state high-temperature thermal aging.
文摘In this paper, the composition of HT-7 LHCD system along with its protection systems is introduced. It is very important for us to run the LHCD system safely and efficiently.
文摘<strong>Background: </strong>Numerous studies have demonstrated increasing evidence for cataractogenesis at lower levels of ionizing radiation than previously believed, with some suggesting possible absence of a threshold. Genetic differences between individuals also result in increased susceptibility in some operators, who might not be aware. European occupational exposure limits have been reduced and operators are seeking protective measures. <strong>Objective: </strong>To evaluate the protective effect of a face-shield equipped suspended protection system (Zero-Gravity<span style="white-space:nowrap;"><sup><span style="white-space:nowrap;">®</span></sup></span>, TIDI Products, Neenah, WI) along with adherence to safety practices against radiation dose to the eye lens for an interventional radiologist performing a wide variety of procedures. <strong>Materials and Methods:</strong> In this institutional review board-approved single-institution study, one interventional radiologist wore a highly sensitive personnel monitoring dosimeter badge on the cap near the left eye while performing 299 procedures (3690 fluoroscopy minutes) over 18 consecutive months while utilizing the suspended protection system along with adherence to other generally recommended safety practices and movement away from the field during angiographic power injections. Dosimetry reports and procedural information were retrospectively reviewed. <strong>Results: </strong>Total lens dose equivalent to the left eye over 18 months was 0.11 mSv (annualized dose = 0.073 mSv, or 7.3 mRem). The patient-dose-area product standardized dose of 0.00576 <span style="white-space:nowrap;"><span style="white-space:nowrap;"><span style="white-space:nowrap;">μ</span></span></span>Sv/Gy<span style="white-space:nowrap;"><span style="white-space:nowrap;">⋅</span></span>cm<sup>2</sup> is well below reports of conventional lead aprons, shields, and protective eyewear. <strong>Conclusion: </strong>Eye exposures were kept to near-background levels using the materials and methods of this study while performing a wide variety of complex procedures from all positions around the patient.
基金supported by National Natural Science Foundation of China(No.11575240)Key Program of Research and Development of Hefei Science Center,CAS(grant 2016HSC-KPRD002)
文摘Neutral beam injection is one of the effective auxiliary heating methods in magnetic-confinementfusion experiments. In order to acquire the suppressor-grid current signal and avoid the grid being damaged by overheating, a data acquisition and over-current protection system based on the PXI(PCI e Xtensions for Instrumentation) platform has been developed. The system consists of a current sensor, data acquisition module and over-current protection module. In the data acquisition module,the acquired data of one shot will be transferred in isolation and saved in a data-storage server in a txt file. It can also be recalled using NBWave for future analysis. The over-current protection module contains two modes: remote and local. This gives it the function of setting a threshold voltage remotely and locally, and the forbidden time of over-current protection also can be set by a host PC in remote mode. Experimental results demonstrate that the data acquisition and overcurrent protection system has the advantages of setting forbidden time and isolation transmission.
文摘China’s trademark business hasmade much progress since thecountry began its reform and open-uppolicy. In 1979 there were only 32,589registered trademarks, of which 5,130were foreign ones. With the establishmentand improvement of the trademarkprotection system, the valid registeredtrademarks had reached 465,865 by theend of 1994, and 70,216 of them were for70 countries and regions. Such speed israre in the world. The features of the country’strademark protection system are asfollows: 1. Definite legal regulations andclear government
文摘This session of the Forum has the theme, “The Chinese Dream: New Progress in the Cause of Human Rights in China.” This theme concentrates on such important subtopics as “The Chinese Dream and Human Rights” ,
文摘In wide area backup protection of electric power systems, the prerequisite of protection device's accurate, fast and reliable performance is its corresponding fault type and fault location can be discriminated quickly and defined exactly. In our study, global information will be introduced into the backup protection system. By analyzing and computing real-time PMU measurements, basing on cluster analysis theory, we are using mainly hierarchical cluster analysis to search after the statistical laws of electrical quantities' marked changes. Then we carry out fast and exact detection of fault components and fault sections, and finally accomplish fault isolation. The facts show that the fault detection of fault component (fault section) can be performed successfully by hierarchical cluster analysis and calculation. The results of hierarchical cluster analysis are accurate and reliable, and the dendrograms of hierarchical cluster analysis are in intuition.
文摘Purpose: This clinical study compares conventional lead aprons and ancillary shields to a functionally weightless personal overhead-supported system with expanded coverage. Materials and Methods: Primary operators performed procedures (N = 126, fluoroscopy minutes = 1209) using one of 2 methods of radiation protection and wearing dosimeters on multiple body locations. Method “LAS” (Lead-Apron+Shields): lead skirt, vest, thyroid shield, with 100% use of under-table shield, side shield, and mobile suspended lead-acrylic shield. Method “Zgrav”: ZeroGravity system (CFI Medical Solutions) with variable use of shielding. The studied early model moving with the operator had a curved lead-acrylic head shield (0.5 mm Pb) and expansive lead apron (0.5 - 1.0 mm Pb) that covered leg to distal calf and proximal arm to elbow, and a drape that permitted sterile entry and exit. Study was institutional review board approved and HIPPA-compliant. Results: Measured with a sensitive electronic dosimeter, eye exposures were 99% (P 0.001) reduced for Zgrav with upgraded face shield vs. LAS, regardless of use or non-use of suspended shield with Zgrav. With optically stimulated luminescence (OSL) dosimeters, operator exposures, standardized to minutes of fluoroscopy and Fluoroscopic Patient Dose Area Product, were reduced by 87% - 100% for eye & head, neck, humerus, and tibia (Zgrav vs. LAS). Overall eye & head exposure reduction for entire study was 94%. Non-equivalence of torso exposures was not demonstrated. A brief user survey showed ergonomic advantages of Zgrav. Conclusion: Compared to conventional lead aprons with shields, the suspended system provided superior operator protection during interventional fluoroscopy, allowing operators to perform procedures without potentially obstructive shields.
文摘This paper examines the use of corrosion inhibitors in order to protect the reinforcement of concrete. For this purpose mortar specimens were constructed with or without corrosion inhibitors and were partially immersed in sodium chloride. Corrosion inhibitors were used as admixture into concrete and were sprayed on the external surface of mortar specimens. In all mortar specimens, electric junction between reinforcements was achieved. The methods that were used for the evaluation of the reinforcement corrosion in concrete, included half-cell potential measurements, polarization curves of reinforced rebars and mass loss of the reinforcement. Finally, the durability of concrete after the use of corrosion inhibitors was also examined.
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institutions
文摘In order to study the dynamic behaviors of the thermal protection system(TPS)and dynamic strength of the strain-isolation-pad(SIP),a two degree-of-freedom dynamic theoretical model is presented under the acoustic excitation and base excitation. The tile and SIP are both considered as the elastic body and simplified as a mass point,a linear spring and a damping element. The theoretical solutions are derived,and the reasonability of theoretical model is verified by comparing the theoretical results with the numerical results. Finally,the influences on the dynamic responses of TPS by the structural damping coefficient of TPS,elasticity modulus and thickness of SIP are analyzed.The results show that the material with higher damping,and SIP with thicker size and lower elastic modulus should be considered to reduce the dynamic responses and intensify the security of TPS. The researches provide a theoretical reference for studying the dynamic behaviors of TPS and the dynamic strength of SIP. Besides,the dynamic theoretical model can be used as a quick analysis tool for analyzing the dynamic responses of TPS during the initial design phase.
基金National Social Science Fund Project“Research on Green Production Behavior and Intervention Mechanism of Aquaculture Farmers from the Perspective of Information Transmission”[Grant number.19CGL039].
文摘The issue of marine ecology is an institutional one.China’s marine ecological protection system has gone through a process of development from scratch to existence and from less to more.However,there are still many problems to be solved,such as whether a variety of complex systems can form a joint force of governance,and whether the rear system failures,deficiencies,and conflicts.Therefore,this paper reviews the evolution logic of China’s marine ecological protection system,explores the complementary space of the existing system from the perspective of institutional complementarity,and analyzes the path of institutional reform of supplement,amendment,and coordination,to promote the effective transition of marine ecological protection system emphasizing quality over quantity.The evolution of China’s marine ecological protection system can be divided into three stages:initial establishment,steady progression,and gradual transformation,showing a trend characterized by a changing governance mode from land-sea division to land-sea integration,a changing supervision mode from government only to multi-institution coordination,a changing safeguard mode from standard norms to the legal system.The internal motivation of promoting the evolution of the marine ecological protection system is the link age between the long-overdue institutional derived demand and supply,and between institutional cost constraints and institutional income drivers.Marine ecological protection is a complex and systematic project across regions and departments,and the link age between different ecological protection systems is crucial.Based on the theory of institutional complementarity,this study finds that China’s marine ecological protection system has great complementarity needs in three aspects:protection subject,protection means,and protection process.Among them,the problem of a single unitary protection subject is mainly caused by the lack of system,the low efficiency of protection means is mainly affected by the lack of system adaptability,and the separation of protection process mainly reflects the contradiction of system incongruity and mismatch.Based on this,the supplement of China’s marine ecological protection system should focus on the government’s responsibilities and the cultivation of multiple subjects.The revision of the system should focus on the further improvement of non-governmental mechanisms such as market incentives and information disclosure.The coordination of the system should be based on the whole process from pre regulation preparations to post-regulation review,in order to promote the effective connection and cooperation of policy tools.
文摘The physical protection system of the body consists of the protective organs for vulnerable body parts-functions and the protective countermeasures against invaders (pathogens), but to survive, the body also requires the protective social groups for vulnerable social members-functions and the protective instinctive mental countermeasures against adversities such as hardship, danger, and unfamiliarity-uncertainty. As a result, this paper proposes that the mental protection system of the body consists of the social brain to set up the protective social groups for vulnerable social members-functions and the mental immune system to produce the protective mental countermeasures against adversities. This paper proposes that from the social brain, the protective social groups include alliance group for vulnerable individuals, kinship-friendship group for vulnerable children, interdependent specialists group for vulnerable pregnant females, territorial group for social boundary, connective group for social connection, and competitive group for social competition. From the mental immune system, the mental protective countermeasures include comforter against hardship, hyperactivity against danger, phobia against unfamiliarity-uncertainty, and rationality against unfamiliarity-uncertainty. The overactive mental immune system causes mental allergies and auto immune diseases as personality-mental disorders against ubiquitous harmful and harmless perceived adversities, correlating to physical allergies and auto immune diseases against ubiquitous harmful and harmless detected invaders. The mental protection system also produces personality traits, social moralities, social organizations, social systems, religions, and cultures as described in this paper. The mental protective system is the source of protective behaviors.
文摘Because the leakage protection circuit in traction motor of coal mining machine is impacted by frequency converter devices,malfunctions appear frequently.This paper makes an in-depth analysis,proposes a solution of using the subtraction circuit to offset interference signals and conducts a simulation analysis.The above scheme,which is simple and easily realized,can improve the reliability of leakage protection device in traction motor.