检索结果-南通市图书馆

A reduced-order model for fast predicting ionized flows of hypersonic vehicles along flight trajectory

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2024年第1期37卷 89-105页

作者： Jingchao ZHANG Chunsheng NIE Jinsheng CAI shucheng pan School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Science and Technology on Space Physics Laboratory China Academy of Launch Vehicle TechnologyBeijing 100076China Institute of Extreme Mechanics Northwestern Polytechnical UniversityXi’an 710072China

An improved Reduced-Order Model(ROM)is proposed based on a flow-solution preprocessing operation and a fast sampling strategy to efficiently and accurately predict ionized hypersonic *** ROM is generated in low-dimensional space by performing the Proper Orthogonal Decomposition(POD)on snapshots and is coupled with the Radial Basis Function(RBF)to achieve fast prediction ***,due to the disparate scales in the ionized flow field,the conventional ROM usually generates spurious negative ***,this issue is addressed by performing flow-solution preprocessing in logarithmic space to improve the conventional ***,extra orthogonal polynomials are introduced in the RBF interpolation to achieve additional improvement of the prediction *** addition,to construct high-efficiency snapshots,a trajectory-constrained adaptive sampling strategy based on convex hull optimization is *** evaluate the performance of the proposed fast prediction method,two hypersonic vehicles with classic configurations,i.e.a wave-rider and a reentry capsule,are used to validate the proposed *** two cases show that the proposed fast prediction method has high accuracy near the vehicle surface and the free-stream region where the flow field is *** with the conventional ROM prediction,the prediction results are significantly improved by the proposed method around the discontinuities,*** shock wave and the ionized *** a result,the proposed fast prediction method reduces the error of the conventional ROM by at least 45%,with a speedup of approximately 2.0×105compared to the Computational Fluid Dynamic(CFD)*** test cases demonstrate that the method developed here is efficient and accurate for predicting ionized hypersonic flows.

关键词： Reduced-order model Radial basis function Constrained sampling Transfer function Fast flow prediction Ionized hypersonic flows

Microstructure and Mechanical Property of the Large Cross-Sectioned Mg-Gd-Y-Zn-Zr Alloy Produced by Small Extrusion Ratio

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2024年第6期37卷 999-1006页

作者： Sen Wang Hucheng pan Caixia Jiang Zhihao Zeng Zhen pan Weineng Tang Chubin Yang Yuping Ren Gaowu Qin Key Laboratory for Anisotropy and Texture of Materials(Ministry of Education) College of Materials Science and EngineeringNortheastern UniversityShenyang110819China Mg and Mg Alloy Institute Technology CenterBaosteel Metal Co.LtdChina Baowu Steel GroupShanghai200940China Jiangxi Provincial Engineering Research Center for Magnesium Alloy Gannan Normal UniversityGanzhou341000China

In this work,the microstructure and mechanical properties of large cross-sectioned Mg-9Gd-3Y-1.2Zn-0.5Zr(VWZ931)samples produced by the small extrusion ratio has been *** as-extruded VWZ931 sample with diameter of~30 mm can exhibit the high yield strength(YS)of 339 MPa,ultimate tensile strength(UTS)of 387 MPa and elongation of 8.2%,*** peak-aged,the YS and UTS of the Mg samples were significantly increased to 435 MPa and 467 *** small extrusion ratio leads to the low fraction of dynamic recrystallized(DRX)grains in VWZ931 sample,and the texture hardening effect can be fully utilized to achieve high *** combined effect of precipitation strengthening due to the long-period stacking ordered phases and theβ′phase,grain boundary strengthening due to the fine DRX grains,heterogeneous deformation-induced strengthening caused by bimodal microstructure,can together contribute to the high strength of present Mg *** findings can shed light on designing other large-sized Mg wrought alloys with high mechanical performance.

关键词： Mg-RE alloy Mechanical property Bimodal grains Texture hardening

Hematopoietic aging:Cellular,molecular,and related mechanisms

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Medical Journal 2024年第11期137卷 1303-1312页

作者： Li Ye Chuan Tian Ye Li Hang pan Jinxiu Hu Liping shu Xinghua pan The Stem Cells and Immune Cells Biomedical Techniques Integrated Engineering Laboratory of State and Regions Cell Therapy Technology Transfer Medical Key Laboratory of Yunnan ProvinceKunming Key Laboratory of Stem Cell and Regenerative MedicineBasic Medical Laboratory920th Hospital of Joint Logistics Support ForcePLAKunmingYunnan 650032China Department of Immunology of School of Basic Medicine of Guizhou Medical University National and Local Joint Engineering Laboratory of Cell Engineering Biomedical TechnologyKey Laboratory of Regenerative Medicine of Guizhou ProvinceState Key Laboratory of Efficacy and Utilization of Medicinal Plants Co-constructed by Province and MinistryKey Laboratory of Translational Research of Adult Stem Cell of Chinese Academy of Medical SciencesGuiyangGuizhou 550025China

Aging is accompanied by significant inhibition of hematopoietic and immune system function and disruption of bone marrow ***-related alterations in the inflammatory response,immunity,and stem cell niches are at the root of hematopoietic *** the molecular mechanisms underlying hematopoietic and bone marrow aging can aid the clinical treatment of aging-related *** particular,it is unknown how the niche reprograms hematopoietic stem cells(HSCs)in an age-dependent manner to maintain normal hematopoiesis in elderly ***,specific inhibitors and blood exchange methods have been shown to reshape the hematopoietic niche and reverse hematopoietic ***,we present the latest scientific discoveries related to hematopoietic aging and hematopoietic system rejuvenation,discuss the relationships between hematopoietic niche aging and HSC aging,and describe related studies on stem cell-mediated regulation of hematopoietic aging,aiming to provide new ideas for further study.

关键词： Stem cells Hematopoietic stem cell Niche Hematopoietic aging

Determination method of mesh size for numerical simulation of blast load in near-ground detonation

在线全文

学校读者我要写书评

暂无评论

Defence Technology（防务技术） 2024年第8期38卷 111-125页

作者： Doudou Si Zuanfeng pan Haipeng Zhang College of Civil Engineering Tongji UniversityShanghai 200092China State Key Lab of Disaster Reduction in Civil Engineering Tongji UniversityShanghai 200092China

In order to improve the overall resilience of the urban infrastructures, it is required to conduct blast resistant design for important building structures in the city. For complex terrain in the city, it is recommended to determine the blast load on the structures via numerical simulation. Since the mesh size of the numerical model highly depends on the explosion scenario, there is no generally applicable approach for the mesh size selection. An efficient method to determine the mesh size of the numerical model of near-ground detonation based on explosion scenarios is proposed in this study. The effect of mesh size on the propagation of blast wave under different explosive weights was studied, and the correlations between the mesh size effect and the charge weight or the scaled distance was described. Based on the principle of the finite element method and Hopkinson-Cranz scaling law, a mesh size measurement unit related to the explosive weight was proposed as the criterion for determining the mesh size in the numerical simulation. Finally, the applicability of the method proposed in this paper was verified by comparing the results from numerical simulation and the explosion tests and was verified in AUTODYN.

关键词： Blast load Mesh size effect Numerical simulation Scaled mesh size Verification

On Leray's problem in an infinitely long pipe with the Navier-slip boundary condition

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2024年第4期67卷 819-854页

作者： Zijin Li Xinghong pan Jiaqi Yang School of Mathematics and Statistics Nanjing University of Information Science and TechnologyNanjing 210044China School of Mathematics and Key Laboratory of Ministry of Industry and Information Technology Nanjing University of Aeronautics and AstronauticsNanjing 211106China School of Mathematics and Statistics Northwestern Polytechnical UniversityXi'an 710129China

The original Leray’s problem concerns the well-posedness of weak solutions to the steady incompressible Navier-Stokes equations in a distorted pipe,which approach the Poiseuille flow subject to the no-slip boundary condition at spatial *** this paper,the same problem with the Navier-slip boundary condition instead of the no-slip boundary condition,is *** to the complexity of the boundary condition,some new ideas,presented as follows,are introduced to handle the extra difficulties caused by boundary ***,the Poiseuille flow in the semi-infinite straight pipe with the Navier-slip boundary condition will be introduced,which will serve as the asymptotic profile of the solution to the generalized Leray’s problem at spatial ***,a solenoidal vector function defined in the whole pipe,satisfying the Navierslip boundary condition,having the designated flux and equalling the Poiseuille flow at a large distance,will be carefully *** plays an important role in reformulating our ***,the energy estimates depend on a combined L2-estimate of the gradient and the stress tensor of the velocity.

关键词： stationary Navier-Stokes system Navier-slip boundary condition Leray's problem

同方期刊数据库

Mobile Crowdsourcing Task Allocation Based on Dynamic Self-Attention GANs

在线全文

学校读者我要写书评

暂无评论

Computers, Materials & Continua 2024年第4期79卷 607-622页

作者： Kai Wei Song Yu Qingxian pan School of Computer and Control Engineering Yantai UniversityYantai264005China School of Computer and Information Science Southwest UniversityChongqing400715China

Crowdsourcing technology is widely recognized for its effectiveness in task scheduling and resource *** traditional methods for task allocation can help reduce costs and improve efficiency,they may encounter challenges when dealing with abnormal data flow nodes,leading to decreased allocation accuracy and *** address these issues,this study proposes a novel two-part invalid detection task allocation *** the first step,an anomaly detection model is developed using a dynamic self-attentive GAN to identify anomalous *** to the baseline method,the model achieves an approximately 4%increase in the F1 value on the public *** the second step of the framework,task allocation modeling is performed using a twopart graph matching *** phase introduces a P-queue KM algorithm that implements a more efficient optimization *** allocation efficiency is improved by approximately 23.83%compared to the baseline *** results confirm the effectiveness of the proposed framework in detecting abnormal data nodes,enhancing allocation precision,and achieving efficient allocation.

关键词： Mobile crowdsourcing task allocation anomaly detection GAN attention mechanisms

State-sensitive convolutional sparse coding for potential biomarker identification in brain signals

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Science China(Information Sciences) 2024年第5期67卷 270-286页

作者： Puli WANG Yu QI Gang pan College of Computer Science and Technology Zhejiang University State Key Laboratory of Brain-Machine Intelligence Zhejiang University MOE Frontier Science Center for Brain Science and Brain-machine Integration Zhejiang University Affiliated Mental Health Center & Hangzhou Seventh People's Hospital Zhejiang University School of Medicine

The identification of prototypical waveforms, such as sleep spindles and epileptic spikes, is crucial for the diagnosis of neurological disorders. These prototypical waveforms are usually recurrently presented in certain brain states, serving as potential biomarkers for clinical evaluations. Convolutional sparse coding(CSC) approaches have demonstrated strength in identifying recurrent patterns in time-series. However,existing CSC approaches do not explicitly explore state-specific patterns, making it difficult to identify state-related biomarkers. To address this problem, we propose state-sensitive CSC to learn state-specific prototypical waveforms. Specifically, we model signals of a certain state with specific waveforms that only appear frequently in this state and background waveforms that are independent of states. Based on this,state-sensitive CSC separates state-specific waveforms from background ones explicitly by incorporating incoherence constraints into optimizations. Experiments with epilepsy brain signals demonstrate that our approach can effectively identify prototypical waveforms in pre-ictal states, providing potential biomarkers for seizure prediction. Our approach provides a promising tool for automatic biomarker candidate identification.

关键词： convolutional sparse coding prototypical waveforms state-specific dictionary biomarker identification neural signal processing

Guest editorial:Special Issue on Artificial Intelligence and Emerging Computational Approaches for Tribology

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Friction 2024年第6期12卷 1057-1059页

作者： Zhinan ZHANG shuaihang pan Bart RAEYMAEKERS State Key Laboratory of Mechanical System and Vibration Shanghai Jiao Tong UniversityShanghai 200240China Department of Mechanical Engineering University of UtahSalt Lake CityUT 84112USA Department of Mechanical Engineering Virginia TechBlacksburgVA 24061USA

Tribo-behavior is a complex system-based time-dependent process,and it is difficult to accurately model a tribo-system and predict its ***,tribology research,in most cases,has relied on extensive *** by the artificial intelligence(AI)-for-science revolution,AI and other emerging computational approaches provide opportunities to explore the complex processes in tribo-systems and the physical mechanisms of tribo-behavior in an efficient way,significantly pushing the boundaries of tribology research.

关键词： behavior editorial artificial

Identification of missing CYP450 enzymes involved in paclitaxel biosynthesis and heterologous reconstitution of baccatin III

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Natural Medicines 2024年第4期22卷 291-292页

作者： DU Jinfa LIAO pan LU Xu State Key Laboratory of Natural Medicines School of Traditional Chinese PharmacyChina Pharmaceutical UniversityNanjing 210009China Department of Biology Hong Kong Baptist UniversityKowloon TongHong KongChina State Key Laboratory of Agrobiotechnology The Chinese University of Hong KongHong KongChina State Key Laboratory for Quality Ensurance and Sustainable Use of Dao-di Herbs Beijing 100700China Medical Botanical Garden China Pharmaceutical UniversityNanjing 210009China

Paclitaxel,a tetracyclic diterpenoid,has garnered attention for its potent anti-cancer properties and intricate molecular structure,making it a significant target for chemical synthesis and biosynthesis[1].However,its natural sources are extremely limited,as it is derived exclusively from the bark of endangered genus Taxus plants,which contain paclitaxel in very low concentrations(0.01%−0.05%)[2-3].Recent advances in synthetic biology present promising opportunities to enhance paclitaxel levels in Taxus cell cultures or to enable the reconstitution of its production in heterologous hosts,such as yeast or tobacco(Nicotiana benthamiana).

关键词： Paclitaxel biosynthesis Baccatin III Cytochrome P450 Taxane oxetanase 1 Heterologous reconstitution