Fail-safe topology optimization is valuable for ensuring that optimized structures remain operable even under damaged conditions.By selectively removing material stiffness in patches with a fixed shape,the complex phe...Fail-safe topology optimization is valuable for ensuring that optimized structures remain operable even under damaged conditions.By selectively removing material stiffness in patches with a fixed shape,the complex phenomenon of local failure is modeled in fail-safe topology optimization.In this work,we first conduct a comprehensive study to explore the impact of patch size,shape,and distribution on the robustness of fail-safe designs.The findings suggest that larger sizes and finer distribution of material patches can yield more robust fail-safe structures.However,a finer patch distribution can significantly increase computational costs,particularly for 3D structures.To keep computational efforts tractable,an efficient fail-safe topology optimization approach is established based on the framework of multi-resolution topology optimization(MTOP).Within the MTOP framework,the extended finite element method is introduced to establish a decoupling connection between the analysis mesh and the topology description model.Numerical examples demonstrate that the developed methodology is 2 times faster for 2D problems and over 25 times faster for 3D problems than traditional fail-safe topology optimization while maintaining similar levels of robustness.展开更多
It is an important topic to improve the redundancy of optimized configuration to resist the local failure in topology optimization of continuum structures.Such a fail-safe topology optimization problem has been solved...It is an important topic to improve the redundancy of optimized configuration to resist the local failure in topology optimization of continuum structures.Such a fail-safe topology optimization problem has been solved effectively in the ficld of statics.In this paper,the fail-safe topology optimization problem is extended to the field of frequency topology optimization.Based on the independent continuous mapping(ICM)method,the model of fail-safe topology optimization is established with the objective of minimal weight integrating with the discrete condition of topological variables and the constraint of the fundamental frequency.The fail-safe optimization model established above is substituted by a sequence of subproblems in the form of the quadratic program with exact second-order information and solved efficiently by the dual sequence quadratic programming(DSQP)algorithm.The numerical result reveals that the optimized fail-safe structure has more complex configuration and preserved materials than the structure obtained from the traditional frequency topology optimization,which means that the optimized fail-safe structure has higher redundancy.Moreover,the optimized fail-safe structure guarantees that the natural frequency meets the constraint of fundamental frequency when the local failure ocurs,which can avoid the structural frequency to be sensitive to local failure.The fail-safe optimirzation topology model is proved effective and feasible by four numerical examples.展开更多
In Xenopus, injection of S-adenosylmethionine decarboxylase (SAMDC) mRNA into fertilized eggs or 2-cell stage embryos induces massive cell dissociation and embryo-lysis at the early gastrula stage due toactivation of ...In Xenopus, injection of S-adenosylmethionine decarboxylase (SAMDC) mRNA into fertilized eggs or 2-cell stage embryos induces massive cell dissociation and embryo-lysis at the early gastrula stage due toactivation of the maternal program of apoptosis. We injected SAMDC mRNA into only one of the animalside blastomeres of embryos at different stages of cleavage, and examined the timing of the onset of theapoptotic reaction. In the injection at 4-and 8-cell stages, a considerable number of embryos developed intotadpoles and in the injection at 16-and 32-cell stages, all the embryos became tadpoles, although tadpolesobtained were sometimes abnormal. However, using GFP as a lineage tracer, we found that descendant cellsof the blastomere injected with SAMDC mRNA at 8-to 32-cell stages are confined within the blastocoel atthe early gastrula stage and undergo apoptotic cell death within the blastocoel, in spite of the continued development of the injected embryos. These results indicate that cells overexpressed with SAMDC undergo apoptotic cell death consistently at the early gastrula stage, irrespective of the timing of the mRNA injection.We assume that apoptosis is executed in Xenopus early gastrulae as a 'fall-safe' mechanism to eliminate physiologically-severely damaged cells to save the rest of the embryo.展开更多
This paper proposes an effective reliability design optimizationmethod for fail-safe topology optimization(FSTO)considering uncertainty based on the moving morphable bars method to establish the ideal balance between ...This paper proposes an effective reliability design optimizationmethod for fail-safe topology optimization(FSTO)considering uncertainty based on the moving morphable bars method to establish the ideal balance between cost and robustness,reliability and structural safety.To this end,a performancemeasure approach(PMA)-based doubleloop optimization algorithmis developed tominimize the relative volume percentage while achieving the reliability criterion.To ensure the compliance value of the worst failure case can better approximate the quantified design requirement,a p-norm constraint approach with correction parameter is introduced.Finally,the significance of accounting for uncertainty in the fail-safe design is illustrated by contrasting the findings of the proposed reliabilitybased topology optimization(RBTO)method with those of the deterministic design method in three typical examples.Monte Carlo simulation shows that the relative error of the reliability index of the optimized structure does not exceed 3%.展开更多
Traditional topology optimization methods may lead to a great reduction in the redundancy of the optimized structure due to unexpected material removal at the critical components.The local failure in critical componen...Traditional topology optimization methods may lead to a great reduction in the redundancy of the optimized structure due to unexpected material removal at the critical components.The local failure in critical components can instantly cause the overall failure in the structure.More and more scholars have taken the fail-safe design into consideration when conducting topology optimization.A lot of good designs have been obtained in their research,though limited regarding minimizing structural compliance(maximizing stiffness)with given amount of material.In terms of practical engineering applications considering fail-safe design,it is more meaningful to seek for the lightweight structure with enough stiffness to resist various component failures and/or to meet multiple design requirements,than the stiffest structure only.Thus,this paper presents a fail-safe topology optimization model for minimizing structural weight with respect to stress and displacement constraints.The optimization problem is solved by utilizing the independent continuous mapping(ICM)method combined with the dual sequence quadratic programming(DSQP)algorithm.Special treatments are applied to the constraints,including converting local stress constraints into a global structural strain energy constraint and expressing the displacement constraint explicitly with approximations.All of the constraints are nondimensionalized to avoid numerical instability caused by great differences in constraint magnitudes.The optimized results exhibit more complex topological configurations and higher redundancy to resist local failures than the traditional optimization designs.This paper also shows how to find the worst failure region,which can be a good reference for designers in engineering.展开更多
This study proposes a B-spline-based multiresolution and multimaterial topology optimization(TO)design method for fail-safe structures(FSSs),aiming to achieve efficient and lightweight structural design while ensuring...This study proposes a B-spline-based multiresolution and multimaterial topology optimization(TO)design method for fail-safe structures(FSSs),aiming to achieve efficient and lightweight structural design while ensuring safety and facilitating the postprocessing of topological structures.The approach involves constructing a multimaterial interpolation model based on an ordered solid isotropic material with penalization(ordered-SIMP)that incorporates failsafe considerations.To reduce the computational burden of finite element analysis,we adopt a much coarser analysis mesh and finer density mesh to discretize the design domain,in which the density field is described by the B-spline function.The B-spline can efficiently and accurately convert optimized FSSs into computer-aided design models.The 2D and 3D numerical examples demonstrate the significantly enhanced computational efficiency of the proposed method compared with the traditional SIMP approach,and the multimaterial TO provides a superior structural design scheme for FSSs.Furthermore,the postprocessing procedures are significantly streamlined.展开更多
In DC micro grids and networks,DC-DC power converters having a large number of semiconductor-based power electronic devices are usually adopted to interconnect the renewable sources and flexible loads.Most of the semi...In DC micro grids and networks,DC-DC power converters having a large number of semiconductor-based power electronic devices are usually adopted to interconnect the renewable sources and flexible loads.Most of the semiconductor-based devices suffer from poor fault withstanding abilities,but conventional power electronic protection schemes have the bottlenecks of the time-delay,self-malfunction and mis-judgement.This paper presents a novel solution using the superconducting fault current limiter(SFCL)to protect a power electronic device and extend the usage to a micro grid.This SFCL is actually a self-triggering,recoverable,and passive current limiter,which does not involve any additional circuit hardware and software.Experimental investigations and simulation analyses clarify the feasibility of using this superconductor-based protection scheme to implement the self-acting fail-safe protection of DC-DC converters.Further system-level simulations explore the SFCL to suppress the over-current and stabilize the bus voltage of a photovoltaic based DC micro grid,particularly facing millisecond-level transients and faults.Our experimental and theoretical investigations lay some technical bases to establish a superconductor-semiconductor-coupled interdisciplinary application from the view from the applied superconductivity,to power electronics,and to micro grids.展开更多
The Internet of Things(IoT)has taken the interconnected world by storm.Due to their immense applicability,IoT devices are being scaled at exponential proportions worldwide.But,very little focus has been given to secur...The Internet of Things(IoT)has taken the interconnected world by storm.Due to their immense applicability,IoT devices are being scaled at exponential proportions worldwide.But,very little focus has been given to securing such devices.As these devices are constrained in numerous aspects,it leaves network designers and administrators with no choice but to deploy them with minimal or no security at all.We have seen distributed denial-ofservice attacks being raised using such devices during the infamous Mirai botnet attack in 2016.Therefore we propose a lightweight authentication protocol to provide proper access to such devices.We have considered several aspects while designing our authentication protocol,such as scalability,movement,user registration,device registration,etc.To define the architecture we used a three-layered model consisting of cloud,fog,and edge devices.We have also proposed several pre-existing cipher suites based on post-quantum cryptography for evaluation and usage.We also provide a fail-safe mechanism for a situation where an authenticating server might fail,and the deployed IoT devices can self-organize to keep providing services with no human intervention.We find that our protocol works the fastest when using ring learning with errors.We prove the safety of our authentication protocol using the automated validation of Internet security protocols and applications tool.In conclusion,we propose a safe,hybrid,and fast authentication protocol for authenticating IoT devices in a fog computing environment.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.12172095,11832009,and 12302008)the Natural Science Foundation of Guangdong Province(Grant No.2023A1515011770)Guangzhou Science and Technology Planning Project(Grant Nos.202201010570,202201020239,202201020193,and 202201010399)。
文摘Fail-safe topology optimization is valuable for ensuring that optimized structures remain operable even under damaged conditions.By selectively removing material stiffness in patches with a fixed shape,the complex phenomenon of local failure is modeled in fail-safe topology optimization.In this work,we first conduct a comprehensive study to explore the impact of patch size,shape,and distribution on the robustness of fail-safe designs.The findings suggest that larger sizes and finer distribution of material patches can yield more robust fail-safe structures.However,a finer patch distribution can significantly increase computational costs,particularly for 3D structures.To keep computational efforts tractable,an efficient fail-safe topology optimization approach is established based on the framework of multi-resolution topology optimization(MTOP).Within the MTOP framework,the extended finite element method is introduced to establish a decoupling connection between the analysis mesh and the topology description model.Numerical examples demonstrate that the developed methodology is 2 times faster for 2D problems and over 25 times faster for 3D problems than traditional fail-safe topology optimization while maintaining similar levels of robustness.
基金the National Natural Science Foundation of China(Grant 11872080).
文摘It is an important topic to improve the redundancy of optimized configuration to resist the local failure in topology optimization of continuum structures.Such a fail-safe topology optimization problem has been solved effectively in the ficld of statics.In this paper,the fail-safe topology optimization problem is extended to the field of frequency topology optimization.Based on the independent continuous mapping(ICM)method,the model of fail-safe topology optimization is established with the objective of minimal weight integrating with the discrete condition of topological variables and the constraint of the fundamental frequency.The fail-safe optimization model established above is substituted by a sequence of subproblems in the form of the quadratic program with exact second-order information and solved efficiently by the dual sequence quadratic programming(DSQP)algorithm.The numerical result reveals that the optimized fail-safe structure has more complex configuration and preserved materials than the structure obtained from the traditional frequency topology optimization,which means that the optimized fail-safe structure has higher redundancy.Moreover,the optimized fail-safe structure guarantees that the natural frequency meets the constraint of fundamental frequency when the local failure ocurs,which can avoid the structural frequency to be sensitive to local failure.The fail-safe optimirzation topology model is proved effective and feasible by four numerical examples.
文摘In Xenopus, injection of S-adenosylmethionine decarboxylase (SAMDC) mRNA into fertilized eggs or 2-cell stage embryos induces massive cell dissociation and embryo-lysis at the early gastrula stage due toactivation of the maternal program of apoptosis. We injected SAMDC mRNA into only one of the animalside blastomeres of embryos at different stages of cleavage, and examined the timing of the onset of theapoptotic reaction. In the injection at 4-and 8-cell stages, a considerable number of embryos developed intotadpoles and in the injection at 16-and 32-cell stages, all the embryos became tadpoles, although tadpolesobtained were sometimes abnormal. However, using GFP as a lineage tracer, we found that descendant cellsof the blastomere injected with SAMDC mRNA at 8-to 32-cell stages are confined within the blastocoel atthe early gastrula stage and undergo apoptotic cell death within the blastocoel, in spite of the continued development of the injected embryos. These results indicate that cells overexpressed with SAMDC undergo apoptotic cell death consistently at the early gastrula stage, irrespective of the timing of the mRNA injection.We assume that apoptosis is executed in Xenopus early gastrulae as a 'fall-safe' mechanism to eliminate physiologically-severely damaged cells to save the rest of the embryo.
基金supported by the National Natural Science Foundation of China(Grant No.12172114)Natural Science Foundation of Anhui Province(Grant No.2008085QA21)+1 种基金Fundamental Research Funds for the Central Universities(Grant No.JZ2022HGTB0291)China Postdoctoral Science Foundation(Grant No.2022M712358).
文摘This paper proposes an effective reliability design optimizationmethod for fail-safe topology optimization(FSTO)considering uncertainty based on the moving morphable bars method to establish the ideal balance between cost and robustness,reliability and structural safety.To this end,a performancemeasure approach(PMA)-based doubleloop optimization algorithmis developed tominimize the relative volume percentage while achieving the reliability criterion.To ensure the compliance value of the worst failure case can better approximate the quantified design requirement,a p-norm constraint approach with correction parameter is introduced.Finally,the significance of accounting for uncertainty in the fail-safe design is illustrated by contrasting the findings of the proposed reliabilitybased topology optimization(RBTO)method with those of the deterministic design method in three typical examples.Monte Carlo simulation shows that the relative error of the reliability index of the optimized structure does not exceed 3%.
基金This work showed in this paper has been supported by the National Natural Science Foundation of China(Grant 11872080).
文摘Traditional topology optimization methods may lead to a great reduction in the redundancy of the optimized structure due to unexpected material removal at the critical components.The local failure in critical components can instantly cause the overall failure in the structure.More and more scholars have taken the fail-safe design into consideration when conducting topology optimization.A lot of good designs have been obtained in their research,though limited regarding minimizing structural compliance(maximizing stiffness)with given amount of material.In terms of practical engineering applications considering fail-safe design,it is more meaningful to seek for the lightweight structure with enough stiffness to resist various component failures and/or to meet multiple design requirements,than the stiffest structure only.Thus,this paper presents a fail-safe topology optimization model for minimizing structural weight with respect to stress and displacement constraints.The optimization problem is solved by utilizing the independent continuous mapping(ICM)method combined with the dual sequence quadratic programming(DSQP)algorithm.Special treatments are applied to the constraints,including converting local stress constraints into a global structural strain energy constraint and expressing the displacement constraint explicitly with approximations.All of the constraints are nondimensionalized to avoid numerical instability caused by great differences in constraint magnitudes.The optimized results exhibit more complex topological configurations and higher redundancy to resist local failures than the traditional optimization designs.This paper also shows how to find the worst failure region,which can be a good reference for designers in engineering.
基金the National Natural Science Foundation of China(Grant No.52075184)the Open-funding Project of State Key Laboratory of Digital Manufacturing Equipment and Technology(Huazhong University of Science and Technology),China(Grant No.DMETKF2021020).
文摘This study proposes a B-spline-based multiresolution and multimaterial topology optimization(TO)design method for fail-safe structures(FSSs),aiming to achieve efficient and lightweight structural design while ensuring safety and facilitating the postprocessing of topological structures.The approach involves constructing a multimaterial interpolation model based on an ordered solid isotropic material with penalization(ordered-SIMP)that incorporates failsafe considerations.To reduce the computational burden of finite element analysis,we adopt a much coarser analysis mesh and finer density mesh to discretize the design domain,in which the density field is described by the B-spline function.The B-spline can efficiently and accurately convert optimized FSSs into computer-aided design models.The 2D and 3D numerical examples demonstrate the significantly enhanced computational efficiency of the proposed method compared with the traditional SIMP approach,and the multimaterial TO provides a superior structural design scheme for FSSs.Furthermore,the postprocessing procedures are significantly streamlined.
基金the National Natural Science Foundation of China[Grant No.51807128].
文摘In DC micro grids and networks,DC-DC power converters having a large number of semiconductor-based power electronic devices are usually adopted to interconnect the renewable sources and flexible loads.Most of the semiconductor-based devices suffer from poor fault withstanding abilities,but conventional power electronic protection schemes have the bottlenecks of the time-delay,self-malfunction and mis-judgement.This paper presents a novel solution using the superconducting fault current limiter(SFCL)to protect a power electronic device and extend the usage to a micro grid.This SFCL is actually a self-triggering,recoverable,and passive current limiter,which does not involve any additional circuit hardware and software.Experimental investigations and simulation analyses clarify the feasibility of using this superconductor-based protection scheme to implement the self-acting fail-safe protection of DC-DC converters.Further system-level simulations explore the SFCL to suppress the over-current and stabilize the bus voltage of a photovoltaic based DC micro grid,particularly facing millisecond-level transients and faults.Our experimental and theoretical investigations lay some technical bases to establish a superconductor-semiconductor-coupled interdisciplinary application from the view from the applied superconductivity,to power electronics,and to micro grids.
文摘The Internet of Things(IoT)has taken the interconnected world by storm.Due to their immense applicability,IoT devices are being scaled at exponential proportions worldwide.But,very little focus has been given to securing such devices.As these devices are constrained in numerous aspects,it leaves network designers and administrators with no choice but to deploy them with minimal or no security at all.We have seen distributed denial-ofservice attacks being raised using such devices during the infamous Mirai botnet attack in 2016.Therefore we propose a lightweight authentication protocol to provide proper access to such devices.We have considered several aspects while designing our authentication protocol,such as scalability,movement,user registration,device registration,etc.To define the architecture we used a three-layered model consisting of cloud,fog,and edge devices.We have also proposed several pre-existing cipher suites based on post-quantum cryptography for evaluation and usage.We also provide a fail-safe mechanism for a situation where an authenticating server might fail,and the deployed IoT devices can self-organize to keep providing services with no human intervention.We find that our protocol works the fastest when using ring learning with errors.We prove the safety of our authentication protocol using the automated validation of Internet security protocols and applications tool.In conclusion,we propose a safe,hybrid,and fast authentication protocol for authenticating IoT devices in a fog computing environment.
