检索结果-南通市图书馆

Rare Metals 2024年第8期43卷 3990-3996页

作者： Jia-Yi Huang Shu-Lan Zuo Qi Zhang Hong-Yang Dai Lei Yang jing-Hua liu Cheng-bao Jiang Key Laboratory of Aerospace Materials and Performance(Ministry of Education) School of Materials Science and EngineeringBeihang UniversityBeijing 100191China

Permanent magnets that can maintain a constant magnetic flux over a wide temperature range are highly desirable in certain applications such as precision instruments.2:17-type SmCo permanent magnets are promising for such instruments owing to their excellent high-temperature magnetic properties that can be further manipulated byadding heavy rare earth elements (HREs).

关键词： magnets permanent earth

Two Matrix Theorems Arising from Nilpotent Groups

在线全文

学校读者我要写书评

暂无评论

Algebra Colloquium 2024年第3期31卷 499-504页

作者： jing Zhao Heguo liu School of Mathematics and Statistics Hainan University Haikou 570228China

For a nilpotent group G without π-torsion,and x,y ∈ G,if x^(n)=y^(n) for a T-number n,then x=y;if x^(m)y^(n)=y^(n)x^(m) for n-numbers m,n,then xy=*** is a wellknown result in group *** this paper,we prove two analogous theorems on matrices,which have independence ***,let m be a given positive integer and A a complex square matrix satisfying that(i)all eigenvalues of A are nonnegative,and(i)rank A^(2)=rank A;then A has a unique m-th root X with rank X^(2)=rank X,all eigenvalues of X are nonnegative,and moreover there is a polynomial f(λ)with X=f(A).In addition,let A and B be complex n×n matrices with all eigenvalues nonnegative,and rank A^(2)=rank A,rank B^(2)=rank B;then(i)A=B when A^(r)=B^(r) for some positive integer r,and(i)AB=BA when A^(s)B^(t)=B^(t)A^(s) for two positive integers s and t.

关键词： nilpotent group root matrix Chinese remainder theorem

Fast and Adaptive Multi-Agent Planning under Collaborative Temporal Logic Tasks via Poset Products

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Research 2024年第2期2024卷 81-94页

作者： Zesen liu Meng Guo Weimin bao Zhongkui Li Deparment of Mechanics and Engineering Science College of EngineeringPeking UniversityBejing 0081 China Science and Technology Commission of China Aerospace Science and Technology Corporation Beijing 100048China

Efficient coordination and planning is essential for large-scale multi-agent systems that collaborate in a shared dynamic environment. Heuristic search methods or learning-based approaches often lack the guarantee on correctness and performance. Moreover, when the collaborative tasks contain both spatial and temporal requirements, e.g., as linear temporal logic (LTL) formulas, formal methods provide a verifiable framework for task planning. However, since the planning complexity grows exponentially with the number of agents and the length of the task formula, existing studies are mostly limited to small artificial cases. To address this issue, a new planning paradigm is proposed in this work for system-wide temporal task formulas that are released online and continually. It avoids two common bottlenecks in the traditional methods, i.e., (a) the direct translation of the complete task formula to the associated B點hi automaton and (b) the synchronized product between the B點hi automaton and the transition models of all agents. Instead, an adaptive planning algorithm is proposed, which computes the product of relaxed partially ordered sets (R-posets) on-the-fly and assigns these subtasks to the agents subject to the ordering constraints. It is shown that the first valid plan can be derived with a polynomial time and memory complexity with respect to the system size and the formula length. Our method can take into account task formulas with a length of more than 400 and a fleet with more than 400 agents, while most existing methods fail at the formula length of 25 within a reasonable duration. The proposed method is validated on large fleets of service robots in both simulation and hardware experiments.

关键词： hardware service system

Cordyceps as potential therapeutic agents for atherosclerosis

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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 mycelium 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

Improvement of Microstructure and Mechanical Properties of Rapid Cooling Friction Stir-welded A1050 Pure Aluminum

在线全文

学校读者我要写书评

暂无评论

Journal of Wuhan University of Technology(Materials Science) 2024年第1期39卷 134-141页

作者：许楠 liu Lutao SONG Qining ZHAO Jianhua bao Yefeng College of Materials Science and Engineering Hohai UniversityChangzhou 213200China

Two-mm thick A1050 pure aluminum plates were successfully joined by conventional and rapid cooling friction stir welding(FSW), respectively. The microstructure and mechanical properties of the welded joints were investigated by electron backscatter diffraction characterization, Vickers hardness measurements, and tensile testing. The results showed that liquid CO_(2) coolant significantly reduced the peak temperature and increased the cooling rate, so the rapidly cooled FSW joint exhibited fine grains with a large number of dislocations. The grain refinement mechanism of the FSW A1050 pure aluminum joint was primarily attributed to the combined effects of continuous dynamic recrystallization, grain subdivision, and geometric dynamic recrystallization. Compared with conventional FSW, the yield strength, ultimate tensile strength, and fracture elongation of rapidly cooled FSW joint were significantly enhanced, and the welding efficiency was increased from 80% to 93%. The enhanced mechanical properties and improved synergy of strength and ductility were obtained due to the increased dislocation density and remarkable grain refinement. The wear of the tool can produce several WC particles retained in the joint, and the contribution of second phase strengthening to the enhanced strength should not be ignored.

关键词： aluminum alloy friction stir welding recrystallization microstructure mechanical properties

Study of deep transportation and plugging performance of deformable gel particles in porous media

在线全文

学校读者我要写书评

暂无评论

Petroleum Science 2024年第2期21卷 962-973页

作者： Wen-jing Zhao jing Wang Zhong-Yang Qi Hui-Qing liu National Key Laboratory of Petroleum Resources and Engineering China University of PetroleumBeijing102249China MOE Key Laboratory of Petroleum Engineering China University of PetroleumBeijing102249China

Deformable gel particles(DGPs) possess the capability of deep profile control and flooding. However, the deep migration behavior and plugging mechanism along their path remain unclear. Breakage, an inevitable phenomenon during particle migration, significantly impacts the deep plugging effect. Due to the complexity of the process, few studies have been conducted on this subject. In this paper, we conducted DGP flow experiments using a physical model of a multi-point sandpack under various injection rates and particle sizes. Particle size and concentration tests were performed at each measurement point to investigate the transportation behavior of particles in the deep part of the reservoir. The residual resistance coefficient and concentration changes along the porous media were combined to analyze the plugging performance of DGPs. Furthermore, the particle breakage along their path was revealed by analyzing the changes in particle size along the way. A mathematical model of breakage and concentration changes along the path was established. The results showed that the passage after breakage is a significant migration behavior of particles in porous media. The particles were reduced to less than half of their initial size at the front of the porous media. Breakage is an essential reason for the continuous decreases in particle concentration, size, and residual resistance coefficient. However, the particles can remain in porous media after breakage and play a significant role in deep plugging. Higher injection rates or larger particle sizes resulted in faster breakage along the injection direction, higher degrees of breakage, and faster decreases in residual resistance coefficient along the path. These conditions also led to a weaker deep plugging ability. Smaller particles were more evenly retained along the path, but more particles flowed out of the porous media, resulting in a poor deep plugging effect. The particle size is a function of particle size before inject

关键词： Physical simulation Deformable gel particle Breakage Particle size Residual resistance coefficient

Diagnosis of the Kinetic Energy of the“21·7”Extreme Torrential Rainfall Event in Henan Province,China

在线全文

学校读者我要写书评

暂无评论

Advances in Atmospheric Sciences 2024年第1期41卷 73-83页

作者： Xiuping YAO Ruoying LI Xiaohong bao Qiaohua liu China Meteorological Administration Training Centre Beijing 100081China State Key Laboratory of Severe Weather Chinese Academy of Meteorological SciencesBeijing 100081China College of Atmospheric Sciences Nanjing University of Information Science and TechnologyNanjing 210044China

An extreme torrential rain(ETR)event occurred in Henan Province,China,during 18-21 July *** on hourly rain-gauge observations and ERA5 reanalysis data,the ETR was studied from the perspective of kinetic energy(K),which can be divided into rotational wind(V_(R))kinetic energy(K_(R)),divergent wind kinetic energy(K_(D)),and the kinetic energy of the interaction between the divergent and rotational winds(K_(RD)).According to the hourly precipitation intensity variability,the ETR process was divided into an initial stage,a rapid increase stage,and maintenance *** showed that the intensification and maintenance of ETR were closely related to the upper-level K,and most closely related to the upperlevel K_(R),with a correlation coefficient of up to *** particular,the peak value of hourly rainfall intensity lagged behind the K_(R) by 8 ***,diagnosis showed that K transformation from unresolvable to resolvable scales made the ETR increase *** meridional rotational wind(u_(R))and meridional gradient of the geopotential(φ)jointly determined the conversion of available potential energy(APE)to K_(R) through the barotropic process,which dominated the rapid enhancement of K_(R) and then caused the rapid increase in *** transportation of K by rotational wind consumed K_(R),and basically offset the K_(R) produced by the barotropic process,which basically kept K_(R) stable at a high value,thus maintaining the ETR.

关键词： extreme torrential rain rotational kinetic energy kinetic energy generation and transport barotropic process

Aptamer-Based Antibiotic Electrochemical Detection Platform Using Portable Plastic Gold Electrode and Multichannel Chip

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 2024年第2期42卷 171-176页

作者： Yin bao Kaiwei Cai Yichen liu Bingling Li Changchun Institute of Applied Chemistry Chinese Academy of SciencesChangchunJilin 130022China School of Applied Chemistry and Engineering University of Science and Technology of ChinaHefeiAnhui 230026China

The development of accurate,rapid and practical electrochemical sensing technology for antibiotic detection has an important application prospect in many fields such as food safety,environmental monitoring,medical and health *** this research,kanamycin specific DNA aptamer and its partially complementary short chain were self-assembled onto the surface of an integrated portable plastic gold electrode(PGE)by Au-s bond,and a simple kanamycin electrochemical biosensor interface was *** the same time,the epoxy resin channel layer was designed,and the auxiliary instrument was set up independently in the laboratory,which could help to measure and analyze eight groups of samples automatically in *** quantitative analysis results showed that in 20 min,the sensor had a good linear relationship between the peak current change of square wave voltammetry and the negative logarithm of kanamycin concentration when kanamycin concentration was in the range of 1-10o0μmol/L,and the detection limit could reach 0.40μmol/*** addition,the discrimination could be achieved within 5 min in the real-time analysis *** sensor had a simple construction method,good selectivity and stability,and could be used for rapid or real-time detection of kanamycin residues in actual water samples,which provided a new direction for the practical detection of kanamycin in environmental watersamples.

关键词： Biosensor Aptamer Antibiotics Electroanalysis DNA

Impact of Carbon Chain Structures in the Backbone on the Flexibility of Modified Polyarylene Sulfide Resins: Molecular Dynamics Simulations and Mesoscopic Analysis

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 Polymer Science 2024年第4期42卷 544-557页

作者： Chi Zhang Rong liu jing-Yuan liu Wen-Wei Jiang Key Laboratory of Fine Chemical Engineering and Functional Materials School of Chemical EngineeringSichuan UniversityChengdu610065China

In the domain of high-performance engineering polymers, the enhancement of mechanical flexibility in poly(phenylene sulfide) (PPS) resins has long posed a significant challenge. A novel molecular structure, designated as PP-He-IS, wherein imide rings and an aliphatic hexylene chain are covalently incorporated into the PPS backbone to enhance its flexibility, is introduced in this study. Molecular dynamics (MD) simulations are employed to systematically explore the effects of diversifying the backbone chain structures by substituting phenyl units with alkyl chains of varying lengths, referred to as PP-A-IS where “A” signifies the distinct intermediary alkyl chain configurations. Computational analyses reveal a discernable decrement in the glass transition temperature (Tg) and elastic modulus, counterbalanced by an increment in yield strength as the alkyl chain length is extended. Notably, the PP-He-IS variant is shown to exhibit superior yield strength while simultaneously maintaining reduced elastic modulus and Tg values, positioning it as an advantageous candidate for flexible PPS applications. Mesoscopic analyses further indicate that structures such as PP-He-IS, PP-Pe-IS, and PP-Bu-IS manifest remarkable flexibility, attributable to the presence of freely rotatable carbon-carbon single bonds. Experimental validation confirms that a melting temperature of 504 K which is lower than that of conventional PPS, and lower crystallinity are exhibited by PP-He-IS, thereby affording enhanced processability without compromising inherent thermal stability. Novel insights into the strategic modification of PPS for mechanical flexibility are thus furnished by this study, which also accentuates the pivotal role played by molecular dynamics simulations in spearheading high-throughput investigations in polymer material modifications.

关键词： Molecular dynamics simulations Polyarylene Sulfide Main-chain modifications Flexibility Aliphatic hexylene chain

Research progress of slippage characteristic and gas film stability enhancement methods on biomimetic hydrophobic surfaces

在线全文

学校读者我要写书评

暂无评论

Journal of Hydrodynamics 2024年第1期36卷 87-101页

作者： Meng-zhuo Zhang Hai-bao Hu liu-zhen Ren Lu-yao bao Jun Wen Luo Xie School of Marine Science and Technology Northwestern Polytechnical UniversityXi’an710072China Research and Development Institute of Northwestern Polytechnical University in Shenzhen Shenzhen518063China

The biomimetic hydrophobic surface is a potentially efficient underwater drag reduction method and the drag reduction mechanism of this kind of surface comes from the interfacial *** now,it is a hotspot to grasp the slippage characteristic and explore slippage enhancement *** paper not only summarizes our numerical simulation and experimental results of slippage characteristic at the solid-liquid interface(SLI)of hydrophobic surfaces(HS)and the gas-liquid interface(GLI)of superhydrophobic surfaces(SHS)in recent years,but also introduces some innovative methods that can effectively improve the gas film stability and drag reduction effect of ***,we used the molecular dynamics(MD)simulation method to figure out the effect of the solid-liquid interaction strength,the system temperature and the shear rate on the slippage of SLI,and expound their action mechanism from molecular ***,by MD and multibody dissipative particle dynamics(MDPD)method,the slippage behavior at the GLI was studied under the influence of the microstructure size and the flow driving *** proposed a new kind of hybrid slip boundary condition model to describe the slippage characteristic on *** addition,we found through experiment that a three-dimensional backflow will appear on the GLI under the interfacial adsorption of surfactants,and the backflow direction will reverse with the change of GLI ***,we put forward the wettability step structure and gas injection method to enhance the stability and drag reduction effect of the gas film on SHS.

关键词： Hydrophobic surface superhydrophobic surface interfacial slip underwater drag reduction