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A stable staggered-grid finite-difference scheme for acoustic modeling beyond conventional stability limit

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Petroleum Science 2024年第1期21卷 182-194页

作者： Jing-yi Xu Yang liu National Key Laboratory of Petroleum Resources and Engineering China University of Petroleum(Beijing)Beijing 102249China china university of Petroleum(Beijing) Karamay CampusKaramay 834000XinjiangChina

Staggered-grid finite-difference(SGFD)schemes have been widely used in acoustic wave modeling for geophysical *** improved methods are proposed to enhance the accuracy of numerical ***,these methods are inevitably limited by the maximum courant-Friedrichs-Lewy(cFL)numbers,making them unstable when modeling with large time sampling intervals or small grid *** solve this problem,we extend a stable SGFD scheme by controlling SGFD dispersion relations and maximizing the maximum cFL ***,to improve modeling stability,we minimize the error between the FD dispersion relation and the exact relation in the given wave-number region,and make the FD dispersion approach a given function outside the given wave-number area,thus breaking the conventional limits of the maximum cFL ***,to obtain high modeling accuracy,we use the SGFD scheme based on the Remez algorithm to compute the FD *** addition,the hybrid absorbing boundary condition is adopted to suppress boundary reflections and we find a suitable weighting coefficient for the proposed *** derivation and numerical modeling demonstrate that the proposed scheme can maintain high accuracy in the modeling process and the value of the maximum cFL number of the proposed scheme can exceed that of the conventional SGFD scheme when adopting a small maximum effective wavenumber,indicating that the proposed scheme improves stability during the modeling.

关键词： Acoustic wave Staggered-grid finite-difference(SGFD) modeling courant-friedrichs-lewy(cFL)number Stability

Optimal cooperative Secondary control for Islanded Dc Microgrids via a Fully Actuated Approach

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IEEE/cAA Journal of Automatica Sinica 2024年第2期11卷 405-417页

作者： yi Yu Guo-Ping liu yi Huang Peng Shi IEEE Shenzhen Key Laboratory of control Theory and Intelligent Systems Southern University of Science and TechnologyShenzhen 518055China School of Electrical Engineering and Automation Wuhan UniversityWuhan 430072China School of Electrical and Mechanical Engineering the University of AdelaideSA 5005Australia Research and Innovation centre Obuda University1034 BudapestHungary

Dc-Dc converter-based multi-bus Dc microgrids(MGs) in series have received much attention, where the conflict between voltage recovery and current balancing has been a hot topic. The lack of models that accurately portray the electrical characteristics of actual MGs while is controller design-friendly has kept the issue active. To this end, this paper establishes a large-signal model containing the comprehensive dynamical behavior of the Dc MGs based on the theory of high-order fully actuated systems, and proposes distributed optimal control based on this. The proposed secondary control method can achieve the two goals of voltage recovery and current sharing for multi-bus Dc MGs. Additionally, the simple structure of the proposed approach is similar to one based on droop control, which allows this control technique to be easily implemented in a variety of modern microgrids with different configurations. In contrast to existing studies, the process of controller design in this paper is closely tied to the actual dynamics of the MGs. It is a prominent feature that enables engineers to customize the performance metrics of the system. In addition, the analysis of the stability of the closed-loop Dc microgrid system, as well as the optimality and consensus of current sharing are given. Finally, a scaled-down solar and battery-based microgrid prototype with maximum power point tracking controller is developed in the laboratory to experimentally test the efficacy of the proposed control method.

关键词： Dc microgrids distributed control high-order fully actuated system approach linear quadratic regulator microgrid modeling secondary control

Atomistic study on the microscopic mechanism of grain boundary embrittlement induced by small dense helium bubbles in iron

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Nuclear Science and Techniques 2024年第3期35卷 84-95页

作者： Lei Peng Yong-Jie Sun Jing-yi Shi yi-Fei liu Shang-Ming chen liu-liu Li State Key Laboratory of Particle Detection and Electronics University of Science and Technology of ChinaHefei 230026China School of Nuclear Science and Technology University of Science and Technology of ChinaHefei 230027China Science and Technology on Reactor System Design Technology Laboratory Nuclear Power Institute of ChinaChengdu 610213China

The helium bubbles induced by 14 MeV neutron irradiation can cause intergranular fractures in reduced activation ferritic martensitic steel,which is a candidate structural material for fusion *** order to elucidate the susceptibility of different grain boundaries(GBs)to helium-induced embrittlement,the tensile fracture processes of 10 types of GBs with and without helium bubbles in body-centered cubic(bcc)iron at the relevant service temperature of 600 K were investigated via molecular dynamics *** results indicate that in the absence of helium bubbles,the GBs studied here can be classified into two distinct categories:brittle GBs and ductile *** atomic scale analysis shows that the plastic deformation of ductile GB at high temperatures originates from complex plastic deformation mechanisms,including the Bain/Burgers path phase transition and deformation twinning,in which the Bain path phase transition is the most dominant plastic deformation ***,the presence of helium bubbles severely inhibits the plastic deformation channels of the GBs,resulting in a significant decrease in elongation at *** bubble-decorated GBs,the ultimate tensile strength increases with the increase in the misorientation ***,the coherent twin boundary∑3{112}was found to maintain relatively high fracture strength and maximum failure strain under the influence of helium bubbles.

关键词： Helium bubble Grain boundary Embrittlement Reduced activation ferritic martensitic steel Molecular dynamics Bain path

cordyceps as potential therapeutic agents for atherosclerosis

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Journal of Integrative Medicine 2024年第2期22卷 102-114页

作者： yi Zhang Si-jing liu School of Marxism Chengdu University of Traditional Chinese MedicineChengdu 61137Sichuan ProvinceChina college of Medical Technology Chengdu University of Traditional Chinese MedicineChengdu 611137Sichuan ProvinceChina chongqing Key Laboratory of Sichuan-chongqing co-construction for Diagnosis and Treatment of Infectious Diseases with Integrated chinese and Western Medicine Chengdu University of Traditional Chinese MedicineChengdu 611137Sichuan ProvinceChina

Atherosclerosis is a leading cause of mortality and morbidity *** the challenges in managing atherosclerosis,researchers continue to investigate new treatments and complementary *** is a traditional chinese medicine that has recently gained attention as a potential therapeutic agent for *** studies have demonstrated the effectiveness of cordyceps in treating atherosclerosis through various pharmacological actions,including anti-inflammatory and antioxidant activities,lowering cholesterol,inhibiting platelet aggregation,and modulating apoptosis or autophagy in vascular endothelial ***,the current misuse of the terms cordyceps and Ophiocordyceps sinensis has caused confusion among researchers,and complicated the current academic research on *** review focuses on the chemical composition,pharmacological actions,and underlying mechanisms contributing to the anti-atherosclerotic effects of cordyceps and the myc.lium of Ophiocordyceps *** review provides a resource for the research on the development of new drugs for atherosclerosis from cordyceps.

关键词： Atherosclerosis cordyceps Ophiocordyceps sinensis

Evaluation of water management on arsenic methylation and volatilization in arsenic-contaminated soils strengthened by bioaugmentation and biostimulation

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Journal of Environmental Sciences 2024年第3期137卷 515-526页

作者： Peng chen yi liu Guo-Xin Sun State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental SciencesChinese Academy of SciencesBeijing 100085China Key Laboratory of Aquatic Botany and Watershed Ecology Wuhan Botanical GardenChinese Academy of SciencesWuhan 430074China university of chinese Academy of Sciences Beijing 100049China

Arsenic(As) fate in paddy fields has been one of the most significant current issues due to the strong As accumulation potential of rice plants under fooded conditions. However,no attempt was done to explore As methylation and volatilization under non-fooded conditions. Herein, we investigated the effects of water management on As methylation and volatilization in three arsenic-contaminated soils enhanced by biostimulation with strawderived organic matter and bioaugmentation with genetic engineered Pseudomonas putida KT2440(GE P. putida). under fooded conditions, the application of biochar(Bc), rice straw(RS)and their combination(Bc+RS) increased total As in porewater. However, these effects were greatly attenuated under non-fooded conditions. compared with RS amendment alone, the combination of GE P. putida and RS further promoted the As methylation and volatilization,and the promotion percentage under non-fooded conditions were significantly higher than that under fooded conditions. The combined GE P. putida and RS showed the highest efficiency in As methylation(88 μg/L) and volatilization(415.4 μg/(kg·year)) in the non-fooded soil with moderate As contamination. Finally, stepwise multiple linear regression analysis presented that methylated As, DOc and p H in porewater were the most important factors contributing to As volatilization. Overall, our findings suggest that combination of bioaugmentation with GE P. putida and biostimulation with RS/Bc+RS is a potential strategy for bioremediation of arsenic-contaminated soils by enhancing As methylation and volatilization under non-fooded conditions.

关键词： Arsenic methylation Arsenic volatilization Water management Straw incorporation Bioaugmentation

NONMONOTONE LOcAL MINIMAX METHODS FOR FINDING MULTIPLE SADDLE POINTS

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Journal of computational Mathematics 2024年第3期42卷 851-884页

作者： Wei liu Ziqing Xie Wenfan yi South china Research center for Applied Mathematics and Interdisciplinary Studies South China Normal UniversityGuangzhou 510631China Key Laboratory of computing and Stochastic Mathematics(Ministry of Education) Hunan Normal UniversityChangshaHunan 410081China Hunan Provincial Key Laboratory of Intelligent Information Processing and Applied Mathematics School of MathematicsHunan UniversityChangshaHunan 410082China

In this paper,by designing a normalized nonmonotone search strategy with the BarzilaiBorwein-type step-size,a novel local minimax method(LMM),which is a globally convergent iterative method,is proposed and analyzed to find multiple(unstable)saddle points of nonconvex functionals in Hilbert *** to traditional LMMs with monotone search strategies,this approach,which does not require strict decrease of the objective functional value at each iterative step,is observed to converge faster with less ***,based on a normalized iterative scheme coupled with a local peak selection that pulls the iterative point back onto the solution submanifold,by generalizing the Zhang-Hager(ZH)search strategy in the optimization theory to the LMM framework,a kind of normalized ZH-type nonmonotone step-size search strategy is introduced,and then a novel nonmonotone LMM is *** feasibility and global convergence results are rigorously carried out under the relaxation of the monotonicity for the functional at the iterative ***,in order to speed up the convergence of the nonmonotone LMM,a globally convergent Barzilai-Borwein-type LMM(GBBLMM)is presented by explicitly constructing the Barzilai-Borwein-type step-size as a trial step-size of the normalized ZH-type nonmonotone step-size search strategy in each ***,the GBBLMM algorithm is implemented to find multiple unstable solutions of two classes of semilinear elliptic boundary value problems with variational structures:one is the semilinear elliptic equations with the homogeneous Dirichlet boundary condition and another is the linear elliptic equations with semilinear Neumann boundary *** numerical results indicate that our approach is very effective and speeds up the LMMs significantly.

关键词： Multiple saddle points Local minimax method Barzilai-Borwein gradient method Normalized nonmonotone search strategy Global convergence

Vibration attenuation performance of wind turbine tower using a prestressed tuned mass damper under seismic excitation

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Earthquake Engineering and Engineering Vibration 2024年第2期23卷 511-524页

作者： Lei Zhenbo liu Gang Wang Hui Hui yi School of civil Engineering Chongqing UniversityChongqing 400045China Key Laboratory of New Technology for construction of cities in Mountain Area Chongqing UniversityMinistry of EducationChongqing 400045China

With the rapid development of large megawatt wind turbines,the operation environment of wind turbine towers(WTTs)has become increasingly *** particular,seismic excitation can create a resonance response and cause excessive vibration of the *** investigate the vibration attenuation performance of the WTT under seismic excitations,a novel passive vibration control device,called a prestressed tuned mass damper(PS-TMD),is presented in this ***,a mathematical model is established based on structural dynamics under seismic ***,the mathematical analytical expression of the dynamic coefficient is deduced,and the parameter design method is obtained by system tuning ***,based on a theoretical analysis and parameter design,the numerical results showed that the PS-TMD was able to effectively mitigate the resonance under the harmonic basal ***,the time-history analysis method is used to verify the effectiveness of the traditional pendulum tuned mass damper(PTMD)and the novel PS-TMD device,and the results indicate that the vibration attenuation performance of the PS-TMD is better than the *** addition,the PS-TMD avoids the nonlinear effect due to the large oscillation angle,and has the potential to dissipate hysteretic energy under seismic excitation.

关键词： wind turbine tower prestressed tuned mass damper vibration control seismic excitation numerical simulation

Optimization study of spherical tuyere based on BP neural network and new evaluation index

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Building Simulation 2024年第2期17卷 223-234页

作者： Mengchao liu Ran Gao yi Wang Angui Li School of Building Services Science and Engineering Xi’an University of Architecture and TechnologyXi’an710055China

The energy consumption of heating,ventilation,and air conditioning(HVAc)systems holds a significant position in building energy usage,acc.unting for about 65%of the total energy ***,with the advancement of building automation,the energy consumption of ventilation systems continues to *** study focuses on improving the performance of spherical tuyeres in HVAc *** primarily utilizes neural networks and multi-island genetic algorithms(MIGA)for multi-parameter *** employing methods such as structural parameterization,accurate and fast computational fluid dynamics(cFD)simulations,a minimized sample space,and a rational optimization strategy,the time cycle of the optimization process is ***,a new comprehensive evaluation index is proposed in this research to describe the performance of spherical tuyeres,which can be used to more accurately assess spherical tuyeres with different *** results show that by establishing a neural network prediction model and combining it with the multi-island genetic algorithm,a novel spherical tuyere design was successfully *** optimized novel spherical tuyeres achieved a 27.05%reduction in the spherical tuyeres effective index(STEI)compared to the traditional spherical ***,the resistance decreased by 15.68%,and the jet length increased by 7.57%.The experimental results demonstrate that our proposed optimization method exhibits high accuracy,good generalization capability,and excellent agreement at different Reynolds numbers.

关键词： spherical tuyeres STEI cFD ventilation

Ytterbium modified birnessite MnO_(2) for improving deep oxidation of toluene

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Journal of Rare Earths 2024年第4期42卷 668-675页

作者： Linjiang Sun Yan cheng Yujie liu can yi Faculty of Geosciences and Environmental Engineering Southwest Jiaotong UniversityChengdu611756China

A series of rare earth metals modified birnessite manganese dioxides(RE-Mn)was synthesized by hydrothermal method and their catalytic degradation of toluene was ***-Mn shows the best toluene oxidation activity with the conversion of T50%and T99%at 196 and 226℃,*** physiochemical characterizations identified that the high catalytic performance and excellent stability of Yb-Mn are mainly associated with its higher molar ratios of Mn^(4+)/Mn^(3+),more lattice oxygen(Olatt),and better mobility of surface adsorbed oxygen(O_(ads)).Moreover,it is confirmed that introduction of Yb into birnessite MnO_(2) facilitates the production of acetic acid at lower *** results can aid the design of high-efficiency manganese oxide catalysts for the catalytic combustion of VOcs.

关键词： Manganese oxide Rare earth metal doping Toluene catalytic combustion