Anti-explosion performance and dynamic response of an innovative multi-layer composite explosion containment vessel

An innovative multi-layer composite explosion containment vessel(CECV)utilizing a sliding steel platealuminum honeycomb-fiber cloth sandwich is put forward to improve the anti-explosion capacity of a conventional single-layer explosion containment vessel(SECV).Firstly,a series of experiments and finite element(FE)simulations of internal explosions are implemented to understand the basic anti-explosion characteristics of a SECV and the rationality of the computational models and methods is verified by the comparison between the experimental results and simulation results.Based on this,the CECV is designed in detail and a variety of FE simulations are carried out to investigate effects of the sandwich structure,the explosive quantity and the laying mode of the fiber cloth on anti-explosion performance and dynamic response of the CECV under internal explosions.Simulation results indicate that the end cover is the critical position for both the SECV and CECV.The maximum pressure of the explosion shock wave and the maximum strain of the CECV can be extremely declined compared to those of the SECV.As a result,the explosive quantity the CECV can sustain is up to 20 times of that the SECV can sustain.Besides,as the explosive quantity increases,the internal pressure of the CECV keeps growing and the plastic deformation and failure of the sandwich structure become more and more severe,yielding plastic strain of the CECV in addition to elastic strain.The results also reveal that the laying angles of the fiber cloth's five layers have an impact on the anti-explosion performance of the CECV.For example,the CECV with fiber cloth layered in 0°/45°/90°/45°/0°mode has the optimal anti-capacity,compared to 0°/0°/0°/0°/0°and 0°/30°/60°/30°/0°modes.Overall,owing to remarkable anti-explosion capacity,this CECV can be regarded as a promising candidate for explosion resistance.

Adaptive Event-Triggered Time-Varying Output Group Formation Containment Control of Heterogeneous Multiagent Systems

In this paper,a class of time-varying output group formation containment control problem of general linear hetero-geneous multiagent systems(MASs)is investigated under directed topology.The MAS is composed of a number of tracking leaders,formation leaders and followers,where two different types of leaders are used to provide reference trajectories for movement and to achieve certain formations,respectively.Firstly,compen-sators are designed whose states are estimations of tracking lead-ers,based on which,a controller is developed for each formation leader to accomplish the expected formation.Secondly,two event-triggered compensators are proposed for each follower to evalu-ate the state and formation information of the formation leaders in the same group,respectively.Subsequently,a control protocol is designed for each follower,utilizing the output information,to guide the output towards the convex hull generated by the forma-tion leaders within the group.Next,the triggering sequence in this paper is decomposed into two sequences,and the inter-event intervals of these two triggering conditions are provided to rule out the Zeno behavior.Finally,a numerical simulation is intro-duced to confirm the validity of the proposed results.

Distributed Adaptive Predefined-Time Bipartite Containment Algorithm for Nonlinear Multi-Agent Systems with Actuator Faults

Distributed adaptive predefined-time bipartite containment for a class of second-order nonlinear multi-agent systems are studied with actuator faults.The communication topology of multi-agent systems is fixed and directed.To ensure that followers can reach the convex hull spanned by leaders under the conditions of actuator faults,the sliding mode method is introduced.Control protocol for multi-agent systems demonstrates its effectiveness.Finally,simulations are provided to verify the effectiveness of the proposed algorithm.

Interaction of major facilitator superfamily domain containing 2A with the blood-brain barrier

The functional and structural integrity of the blood-brain barrier is crucial in maintaining homeostasis in the brain microenvironment;however,the molecular mechanisms underlying the formation and function of the blood-brain barrier remain poorly understood.The major facilitator superfamily domain containing 2A has been identified as a key regulator of blood-brain barrier function.It plays a critical role in promoting and maintaining the formation and functional stability of the blood-brain barrier,in addition to the transport of lipids,such as docosahexaenoic acid,across the blood-brain barrier.Furthermore,an increasing number of studies have suggested that major facilitator superfamily domain containing 2A is involved in the molecular mechanisms of blood-brain barrier dysfunction in a variety of neurological diseases;however,little is known regarding the mechanisms by which major facilitator superfamily domain containing 2A affects the blood-brain barrier.This paper provides a comprehensive and systematic review of the close relationship between major facilitator superfamily domain containing 2A proteins and the blood-brain barrier,including their basic structures and functions,cross-linking between major facilitator superfamily domain containing 2A and the blood-brain barrier,and the in-depth studies on lipid transport and the regulation of blood-brain barrier permeability.This comprehensive systematic review contributes to an in-depth understanding of the important role of major facilitator superfamily domain containing 2A proteins in maintaining the structure and function of the blood-brain barrier and the research progress to date.This will not only help to elucidate the pathogenesis of neurological diseases,improve the accuracy of laboratory diagnosis,and optimize clinical treatment strategies,but it may also play an important role in prognostic monitoring.In addition,the effects of major facilitator superfamily domain containing 2A on blood-brain barrier leakage in various diseases and the research progress on cross-blood-brain barrier drug delivery are summarized.This review may contribute to the development of new approaches for the treatment of neurological diseases.

Thermal-hydraulic and stress analysis of AP1000 reactor containment during LOCA in dry cooling mode

Some kinds of break in the reactor coolant system may cause the coolant to exit rapidly from the failure site,which leads to the loss of coolant accident(LOCA).In this paper,a stress analysis of an AP1000 reactor containment is performed in an LOCA,with the passive containment cooling system(PCCS) being available and not available for cooling the wall's containment.The variations in the mechanical properties of the wall's containment,including elastic modulus,strength,and stress,are analyzed using the ABAQUS code.A general two-phase model is applied for modeling thermal-hydraulic behavior inside the containment.Obtained pressure and temperature from thermal-hydraulic models are considered as boundary conditions of the ABAQUS code to obtain distributions of temperature and stress across steel shell of the containment in the accident.The results indicate that if the PCCS fails,the peak pressure inside the containment exceeds the design value.However,the stress would still be lower than the yield stress value,and no risk would threaten the integrity of the containment.

Containment Control of Fractional Order Multi-Agent Systems With Time Delays

In complex environments, many distributed multiagent systems are described with the fractional-order dynamics.In this paper, containment control of fractional-order multiagent systems with multiple leader agents are studied. Firstly,the collaborative control of fractional-order multi-agent systems(FOMAS) with multiple leaders is analyzed in a directed network without delays. Then, by using Laplace transform and frequency domain theorem, containment consensus of networked FOMAS with time delays is investigated in an undirected network, and a critical value of delays is obtained to ensure the containment consensus of FOMAS. Finally, numerical simulations are shown to verify the results.

New lumped-mass-stick model based on modal characteristics of structures: development and application to a nuclear containment building

In this study, a new lumped-mass-stick model （LMSM） is developed based on the modal characteristics of a structure such as eigenvalues and eigenvectors. The simplified model, named the ＂frequency adaptive lumped-massstick model,＂ hasonly a small number of stick elements and nodes to provide the same natural frequencies of the structure and is applied to a nuclear containment building. To investigate the numerical performance of the LMSM, a time history analysis is carried out on both the LMSM and the finite element model （FEM） for a nuclear containment building. A comparison of the results shows that the dynamic responses of the LMSM in terms of displacement and acceleration are almost identical to those of the FEM. In addition, the results in terms of floor response spectra at certain elevations are also in good agreement.

Simulation of hydrogen distribution and effect of Engineering Safety Features (ESFs) on its mitigation in a WWER-1000 containment

In this study, thermal–hydraulic parameters inside the containment of aWWER-1000/v446 nuclear power plant are simulated in a double-ended cold leg accident for short and long times (by using CONTAIN 2.0 and MELCOR 1.8.6 codes), and the effect of the spray system as an engineering safety feature on parameters mitigation is analyzed with the former code. Along with the development of the accident from design basis accident to beyond design basis accident, the Zircaloy–steam reaction becomes the source of in-vessel hydrogen generation. Hydrogen distribution inside the containment is simulated for a long time (using CONTAIN and MELCOR), and the effect of recombiners on its mitigation is analyzed (using MELCOR). Thermal–hydraulic parameters and hydrogen distribution profiles are presented as the outcome of the investigation. By activating the spray system, the peak points of pressure and temperature occur in the short time and remain belowthe maximumdesign values along the accident time. It is also shown that recombiners have a reliable effect on reducing the hydrogen concentration below flame propagation limit in the accident localization area. The parameters predicted by CONTAIN and MELCOR are in good agreement with the final safety analysis report. The noted discrepancies are discussed and explained.

Distributed Containment Control of Networked Nonlinear Second-order Systems With Unknown Parameters

In this paper, we study the containment control problem for nonlinear second-order systems with unknown parameters and multiple stationary/dynamic leaders. The topologies that characterize the interaction among the leaders and the followers are directed graphs. Necessary and sufficient criteria which guarantee the control objectives are established for both stationary leaders(regulation case) and dynamic leaders(dynamic tracking case) based protocols. The final states of all the followers are exclusively determined by the initial values of the leaders and the topology structures. In the regulation case, all the followers converge into the convex hull spanned by the leaders,while in the dynamic tracking case, not only the positions of the followers converge into the convex hull but also the velocities of the followers converge into the velocity convex hull of the leaders.Finally, all the theoretical results are illustrated by numerical simulations.

Aseismic safety analysis of a prestressed concrete containment vessel for CPR1000 nuclear power plant

Abstract： The containment vessel of a nuclear power plant is the last barrier to prevent nuclear reactor radiation. Aseismic safety analysis is the key to appropriate containment vessel design. A prestressed concrete containment vessel （PCCV） model with a semi-infinite elastic foundation and practical arrangement of tendons has been established to analyze the aseismic ability of the CPR1000 PCCV structure under seismic loads and internal pressure. A method to model the prestressing tendon and its interaction with concrete was proposed and the axial force of the prestressing tendons showed that the simulation was reasonable and accurate. The numerical results show that for the concrete structure, the location of the cylinder wall bottom around the equipment hatch and near the ring beam are critical locations with large principal stress. The concrete cracks occurred at the bottom of the PCCV cylinder wall under the peak earthquake motion of 0.50 g, however the PCCV was still basically in an elastic state. Furthermore, the concrete cracks occurred around the equipment hatch under the design internal pressure of 0.4MPa, but the steel liner was still in the elastic stage and its leak-proof function soundness was verified. The results provide the basis for analysis and design of containment vessels.

Investigation of ex-vessel core catcher for SBO accident in VVER-1000/V528 containment using MELCOR code

To mitigate consequences of core melting,an ex-vessel core catcher is investigated in this study.Instructions should be obeyed to cool down the corium caused by core melting.The corium destroys the reactor containment and causes radioactive materials to be released into the environment if it does not cool down well.It is important to build a core catcher system for the reception,localization,and cool down of the molten corium during a severe accident resulting from core melting.In this study,the role of a core catcher in the VVER-1000/v528 reactor containment during a station black out(SBO)accident is evaluated using the MELCOR1.8.6 code.In addition,parametric analyses of the SBO for(i)SBO accidents with emergency core cooling system(ECCS)operation,and(ii)without ECCS operation are performed.Furthermore,thermal–hydraulic analyses in dry and wet cavities with/without water are conducted.The investigations include the reduction of gases resulting from molten–corium–concrete interactions(H_(2),CO,CO_(2)).Core melting,gas production,and the pressure/temperature in the reactor containment are assessed.Additionally,a full investigation pertaining to gas release(H_(2),CO,CO_(2))and the pressure/temperature of the core catcher is performed.Based on MELCOR simulations,a core cavity and a perimeter water channel are the best options for corium cooling and a lower radionuclide release.This simulation is also theoretically investigated and discussed herein.The simulation results show that the core catcher system in addition to an internal sacrificial material reduces the containment pressure from 689 to 580 kPa and the corresponding temperature from 394 to 380 K.Furthermore,it is observed that the amount of gases produced,particularly hydrogen,decreased from 1698 to 1235 kg.Moreover,the presence of supporting systems,including an ECCS with a core catcher,prolonged the core melting time from 16,430 to 28,630 s(in an SBO accident)and significantly decreased the gases produced.

Distributed Robust Containment Control of Linear Heterogeneous Multi-Agent Systems:An Output Regulation Approach

In this paper,we consider the robust output containment problem of linear heterogeneous multi-agent systems under fixed directed networks.A distributed dynamic observer based on the leaders’measurable output was designed to estimate a convex combination of the leaders’states.First,for the case of followers with identical state dimensions,distributed dynamic state and output feedback control laws were designed based on the state-coupled item and the internal model compensator to drive the uncertain followers into the leaders’convex hull within the output regulation framework.Subsequently,we extended theoretical results to the case where followers have nonidentical state dimensions.By establishing virtual errors between the dynamic observer and followers,a new distributed dynamic output feedback control law was constructed using only the states of the compensator to solve the robust output containment problem.Finally,two numerical simulations verified the effectiveness of the designed schemes.

Improving Concrete Containment Structures Associated with Fixed-Cone Valves

Fixed-Cone valves are often used to dissipate energy and regulate flow at the low level outlet works of dams. Fixed-Cone valves, also known as Howell-Bunger valves, create an expanding conical jet allowing the energy of the water to dissipate over a large area. However, in many applications constructing the large stilling basin necessary for these valves is either not possible or not feasible. In order to reduce the relative size of the stilling basin, hoods or concrete containment structures have been used in conjunction with Fixed-Cone valves. This paper discusses the use of baffles in concrete containment structures in order to dissipate energy in a considerably confined space. It was determined that using baffles, in place of a deflector ring and end sill (Used in traditional containment structures.), significantly improves the function of containment structures by reducing downstream flow velocities and improving flow patterns and stability. This information will be useful to engineers allowing them to minimize scour and erosion associated with concrete containment structures.

Lyapunov-Based Output Containment Control of Heterogeneous Multi-Agent Systems With Markovian Switching Topologies and Distributed Delays

This paper considers the mean square output containment control problem for heterogeneous multi-agent systems(MASs)with randomly switching topologies and nonuniform distributed delays.By modeling the switching topologies as a continuous-time Markov process and taking the distributed delays into consideration,a novel distributed containment observer is proposed to estimate the convex hull spanned by the leaders'states.A novel distributed output feedback containment controller is then designed without using the prior knowledge of distributed delays.By constructing a novel switching Lyapunov functional,the output containment control problem is then solved in the sense of mean square under an easily-verifiable sufficient condition.Finally,two numerical examples are given to show the effectiveness of the proposed controller.

Study on Failure Possibility of Full Containment LNG Storage Tanks with API 581 Risk-based Inspection

The total storage of full containment LNG storage tanks is very huge. Once the tank rupture or leakage, the consequence will be unimaginable. Therefore it is necessary to perform the risk-based inspection （RBI） and evaluation on LNG storage tanks, and the analysis on LNG storage tanks failure possibility is especially important in the RBI. Recently, Risk-based inspection （RBI） technology based on API 581 is gradually adopted and has become a new technology to determine economic feasibility and safety of equipment in petrochemical plants. However, there are limitations of applying API 581 to LNG equipment because of the unique structure of LNG storage tank （the metal inner tank and concrete outer tank）. Therefore, a failure probability calculation model suitable for full containment LNG storage tanks is proposed. The domestic inner tank is usually made of 9%Ni, and its failure possibility can be calculate based on API581; the outer tank is usually made of pre-stressed concrete, and the failure possibility of structure durability can be calculated by the method of fuzzy mathematics ; Then the failure possibility of the inner tank and the outer tank will be comprehensive considered by using cellulose model. Finally, by citing a real example, it also detailedly introduces the application of this proposed calculation model in the failure possibility analysis of full containment LNG storage tanks. This study provides a new approach for the evaluation of failure possibility on full containment LNG storage tanks.

Aerosol Removal by Emergency Spray in PWR Containment

During the course of a hypothetical severe accident in a nuclear Pressurized Water Reactor （PWR）, containment reactor is pressurized by steam and hydrogen released from a primary circuit breach and distributed into the containment according to convective flows and steam wall condensation. In addition, core degradation leads to fission products released into the containment. Water spraying is used in the containment as mitigation means in order to reduce pressure, to remove fission products and to enhance the gas mixing in case of presence of hydrogen. This paper presents results of the TOSQAN aerosol program undertaken by the Institute de Radioprotection et de Sfiret6 Nucl6aire （IRSN） devoted to study the aerosol removal by a spray, for typical accidental thermal hydraulic conditions in PWR containment. The TOSQAN facility is a large enclosure devoted to simulate typical accidental thermal hydraulic flow conditions in nuclear PWR containment.

Analysis of maximum pressure in VVER1000/V446 reactor containment for LOCA and MSLB

The highest thermal-hydraulic pressure in the containment occurs when reactor coolant in the first loop and steam in the secondary loop discharge simultaneously,and when the maximum amount of energy from reactor unit enters to containment volume. In this paper, we investigate temperature and pressure variations in the VVER 1000 containment compartments owing to concurrent break in the pipelines of the primary and secondary loops. A two-phase, multicellular model is applied in the presence of non-condensable gases. Convection and conduction through the main heat structures inside the containment are also considered. The predicted results agree well with available data. Maximum values of pressure and temperature in the containment are then calculated and compared to the design values. If LOCA and MSLB occur simultaneously, the maximum pressure would exceed the design value and integrity of the containment would be threatened.

Containment consensus with measurement noises and time-varying communication delays

In this paper,we consider the containment consensus control problem for multi-agent systems with measurement noises and time-varying communication delays under directed networks.By using stochastic analysis tools and algebraic graph theory,we prove that the followers can converge to the convex hull spanned by the leaders in the sense of mean square if the allowed upper bound of the time-varying delays satisfies a certain sufficient condition.Moreover,the time-varying delays are asymmetric for each follower agent,and the time-delay-dependent consensus condition is derived.Finally,numerical simulations are provided to illustrate the effectiveness of the obtained theoretical results.

Two Dimension Finite Element Simulations on the Electromagnetic Containment in Twin-Roll Strip Casting

Distribution of magnetic field and electromagnetic force in twin-roll casting of steels was studied by the method of numericalsimulation in this paper. Two-dimension finite element model, which includes the regions of melt, stainless collar, coil andmagnetic core, has been constructed. By solving magnetic vector potential formulations of quasi-static electromagnetic field,distribution of magnetic flux density and magnetic force at different molten height is determined. Calculated results showedthat intensity of the distribution of magnetic flux density increased linearly with the increased coil current; and the magneticforce in the melt increased as a quadratic cure with creased coil current. More attention was given to the distribution of eddycurrent and magnetic force in the melt, the confine effect at different molten height was also discussed.

Prevalence, Knowledge and Self-Reported Containment Practices about Bedbugs in the Resource-Limited Setting of Ethiopia: A Descriptive Cross-Sectional Survey

Over the past decade, a dramatic rise in bedbug resurgence has become one of the top potential public health hazards. This study was conducted to determine prevalence, knowledge and self-reported containment practices about bedbugs in the resource-limited setting of Ethiopia. A community based, cross-sectional survey was conducted between January and May 2014. Selected 260 respondents were interviewed by the administration of a pre-tested questionnaire on knowledge and practices about bedbug infestation in the resource-limited setting of Ethiopia. Overall, 91.6% (238/260) of the residents had ample awareness on bedbug infestation. The majority of them (97.2%) extremely bothered about infestations because of bad odors (83.8%), insomnia (79.8%), biting (66.9%), and skin rashes (56.9%). A high prevalence of infestation (72.7%) was observed. Bedrooms and main hall/salon were identified as potential high-risk areas. Chi-square exhibited a strong association between sanitary status and housing conditions (χ2 = 40.91;df = 4;P = 0.0001). Besides, there was a strong association between respondents’ monthly income (χ2 = 42.1;df = 6;P = 0.0001) and educational status (χ2 = 26.01;df = 5;P = 0.0001) with the presence or absence of bedbug infestation. Though the majority of respondents had adequate knowledge, they suffer with deprived practices attributable to deficient resources as well as negligence/ignorance. This study emphasizes the following key interventions: 1) community-based awareness campaigns, 2) implementation of sustainable preventive/containment strategies, 3) educational interventions to ensure translation of knowledge into practices, and 4) the implementation of appropriate poverty alleviation programs to enhance the local-residents living-standard in the future.