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Experimental investigation on weak shock wave mitigation characteristics of flexible polyurethane foam and polyurea

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Defence Technology（防务技术） 2024年第1期31卷 179-191页

作者： Shiyu Jia Cheng Wang Wenlong Xu Dong ma Fangfang Qi State Key Laboratory of Explosion Science and Technology Beijing Institute of TechnologyBeijing100081China Institute for Advanced Technology Shandong UniversityJinan250061China

In recent years,explosion shock wave has been considered as a signature injury of the current military *** strong shock wave is lethal to the human body,weak shock wave can cause many more lasting *** investigate the protection ability and characteristics of flexible materials and structures under weak shock wave loading,the blast wave produced by TNT explosive is loaded on the polyurethane foam with the density of 200.0 kg/m3(F-200)and 400.0 kg/m3(F-400),polyurea with the density of 1100.0 kg/m^(3)(P-1100)and structures composed of the two materials,which are intended for individual *** results indicate that the shock wave is attenuated to weak pressure disturbance after interacting with the flexible materials which are not *** shock wave protective capability of single-layer materials is dependent on their thickness,density and microscopic *** overpressure,maximum pressure rise rate and impulse of transmitted wave decrease exponentially with increase in sample *** the same thickness,F-400 provides better protective capability than F-200 while P-1100 shows the best protective capability among the three *** this study,as the materials are not destroyed,F-200 with a thickness more than10.0 mm,F-400 with a thickness more than 4.0 mm,and P-1100 with a thickness more than 1.0 mm can attenuate the overpressure amplitude more than 90.0%.Further,multi-layer flexible composites are *** layer layouts of designed structures and layer thickness of the single-layer materials can affect the protective *** the research range,the structure in which polyurea is placed on the impact side shows the optimal shock wave protective performance,and the thicknesses of polyurea and polyurethane foam are 1.0 mm and 4.0 mm *** overpressure attenuation rate reached maximum value of 93.3%and impulse attenuation capacity of this structure are better than those of s

关键词： Free-field explosion Weak shock wave mitigation Polyurea Polyurethane foam multi-layered composites

The prediction of projectile-target intersection for moving tank based on adaptive robust constraint-following control and interval uncertainty analysis

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Defence Technology（防务技术） 2024年第1期31卷 351-363页

作者： Cong Li Xiuye Wang Yuze ma Fengjie Xu Guolai yang The School of mechanical Engineering Nanjing University of Science and TechnologyNanjing290014PR China Inner mongolia North Heavy Industries Co. Ltd.Baotou014033PR China Nanjing Chenguang Group Co. Ltd.Nanjing210006PR China

To improve the hit probability of tank at high speed,a prediction method of projectile-target intersection based on adaptive robust constraint-following control and interval uncertainty analysis is *** method proposed provides a novel way to predict the impact point of projectile for moving ***,bidirectional stability constraints and stability constraint-following error are constructed using the Udwadia-Kalaba theory,and an adaptive robust constraint-following controller is designed considering ***,the exterior ballistic ordinary differential equation with uncertainties is integrated into the controller,and the pointing control of stability system is extended to the impact-point control of ***,based on the interval uncertainty analysis method combining Chebyshev polynomial expansion and affine arithmetic,a prediction method of projectile-target intersection is ***,the co-simulation experiment is performed by establishing the multi-body system dynamic model of tank and mathematical model of control *** results demonstrate that the prediction method of projectile-target intersection based on uncertainty analysis can effectively decrease the uncertainties of system,improve the prediction accuracy,and increase the hit *** adaptive robust constraint-following control can effectively restrain the uncertainties caused by road excitation and model error.

关键词： Tank stability control Constraint-following Adaptive robust control Uncertainty analysis Prediction of projectile-target intersection

A novel alcohol dehydrogenase in the hyperthermophilic crenarchaeon Hyperthermus butylicus

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mLife 2024年第2期3卷 317-325页

作者： Ching Tse Kesen ma Department of Biology University of WaterlooWaterlooOntarioCanada

Hyperthermus butylicus is a hyperthermophilic crenarchaeon that produces 1-butanol as an end product.A thermostable alcohol dehydrogenase(ADH)must be present in *** to act as the key enzyme responsible for this production;however,the gene that encodes the ADH has not yet been identified.A novel ADH,HbADH2,was purified from a cell-free extract of ***,and its characteristics were *** gene that encodes HbADH2 was demonstrated to be HBUT_RS04850 and annotated as a hypothetical protein in ***2 was found to be a primary-secondary ADH capable of using a wide range of substrates,including butyraldehyde and *** had the highest specificity constant,calculated as k_(cat)/K_(m),with kcat and apparent K_(m) values of 8.00±0.22 s^(-1) and 0.59±0.07 mm,*** apparent Km values for other substrates,including ethanol,1-propanol,2-propanol,butanol,acetaldehyde,propanal,and acetone,were 4.36±0.42,4.69±0.41,3.74±0.46,2.44±0.30,1.27±0.18,1.55±0.20,and 0.68±0.04 mm,*** optimal pH values for catalyzing aldehyde reduction and alcohol oxidation were 6.0 and 9.0,respectively,while the optimal temperature was higher than 90°C due to the increase in enzymatic activity from 60℃ to 90℃.Based on its substrate specificity,enzyme kinetics,and thermostability,HbADH2 may be the ADH that catalyzes the production of 1-butanol in *** putative conserved motif sites for NAD(P)^(+)and iron binding were identified by aligning HbADH2 with previously characterized Fe-containing ADHs.

关键词： butanol hyperthermophile Hyperthermus butylicus novel alcohol dehydrogenase thermostability

Gradient microstructure and superior strength-ductility synergy of AZ61 magnesium alloy bars processed by radial forging with different deformation temperatures

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Journal of materials Science & Technology 2024年第3期170卷 65-77页

作者： Jingfeng Zou Lifeng ma.ya.chun Zhu Ling Qin Yuan Yuan School of mechanical Engineering Taiyuan University of Science and TechnologyTaiyuan 030024China Heavy machinery Engineering Research Center of the ministry Education Taiyuan University of Science and TechnologyTaiyuan 030024China Department of Engineering University of HullCottingham RdHull HU67RXUK National Engineering Research Center for magnesium Alloys Chongqing UniversityChongqing 400044China

Gradient microstructure modification is a cost-efficient strategy for high strength without compromising ductility,which is urgently needed in the fundamental science of engineering *** this study,heterogeneous structures of AZ61 alloy bars with anisotropic gradients(with different grain size distributions from the surface to the center)were observed to exhibit strong strength-ductility synergies under different deformation tem *** results reveal that the grain refinement process under mediumlow temperature deformation conditions(≤350℃)consists of four transition stages along the radial direction,i.e.,twin activations and deformation band formations,dislocation cells and pile-ups,ultrafine sub-grains,and randomly orientated quasi-micron *** deformation temperatures have a great influence on twin activations and deformation band formations,and the high temperature can easily provoke the initiation of non-basal *** deformation bands were determined as a primary nucleation site due to their highly unstable dislocation hindrance *** in combination with the Radial forging(RF)deformation process,the differences of dynamic precipitates can be attributed to microstructural difference and solubility limit of Al at different tem *** summarizing the tensile test results,the sample forged at 350℃exhibited the best strength-ductility synergy,exhibiting the highest elongation(EL)of 23.2%with a 251 mPa yield strength(YS)and 394 mPa ultimate tensile strength(UTS)in center region,and combined with the highest strength value of 256 mPa YS and 420 mPa UTS in the center region,while the EL was slightly degraded to 19.8%.

关键词： Gradient microstructure Radial forging Strength-ductility synergy magnesium alloy Strengthening mechanism

Zircon U-Pb ages in the Nuratau ophiolitic mélange in the southern Tianshan,Uzbekistan:Implication for the closure of Paleo-Asian Ocean

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China Geology 2024年第2期7卷 365-368,I0004-I0007页

作者： Kai Weng Ji-fei Cao Divayev-Farid Karibovich Jahongir-Jurabekovich movlanov Bo Chen Zhong-ping ma Xi’an Center of Geological Survey China Geological SurveyXi’an 710119China The Center for Geoinnovation Technologies Doctor of Sciences in Geology and mineralogy University of Geological ScienceTashkent 100060Uzbekistan

*** The Central Asian Orogenic Belt(CAOB),which is located between the European craton,Siberian craton,and Tarim-North China craton(Fig.1a),is the largest phanerozoic accretionary orogen in the *** resulted from the longterm subduction and accretion of the Paleo-Asian Ocean(PAO).The PAO has been in existence since at least the late mesoproterozoic(about 1020 ma).However,there has been debate about the closing time of the PAO.

关键词： Asian Paleo Tianshan

microED as a powerful technique for the structure determination of complex porous materials

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Chinese Journal of Structural Chemistry 2024年第3期43卷 41-54页

作者： Chao ma Cong Lin Jian Li State Key Laboratory of Coordination Chemistry School of Chemistry and Chemical EngineeringNanjing UniversityNanjing210023China Department of Applied Biology and Chemical Technology The Hong Kong Polytechnic UniversityKowloonHong Kong China

Porous materials have garnered significant attention in recent *** the intrinsic relationship between their structures and properties requires precise knowledge of their atomic ***-crystal X-ray diffraction(SCXRD)has traditionally been the primary method for elucidating such structures,but it demands large,high-quality crystals,often exceeding 5μm in *** growth of these crystals can be a time-consuming process,especially for one-and two-dimensional *** explore structures at the nanoscale,microED(microcrystal electron diffraction(ED))offers unprecedented insights into the realm of *** revolutionary technique enables researchers to uncover intricate details within nanoscale structures,promising to reshape our fundamental understanding of *** this review,we delve into the applications of microED in the study of various porous materials,including zeolites,metal-organic frameworks(mOFs),and covalent organic frameworks(COFs).We emphasize the pivotal role of microED in nanomaterial characterization,enabling precise crystallographic analysis and phase identification.

关键词： Atomic structure microED Porous materials Three-dimensional electron diffraction

A Survey of Knowledge Graph Construction Using machine Learning

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Computer modeling in Engineering & Sciences 2024年第4期139卷 225-257页

作者： Zhigang Zhao Xiong Luo maojian Chen Ling ma School of Computer and Communication Engineering University of Science and Technology BeijingBeijing100083China Shunde Innovation School University of Science and Technology BeijingFoshan528399China Beijing Key Laboratory of Knowledge Engineering for materials Science Beijing100083China

Knowledge graph(KG)serves as a specialized semantic network that encapsulates intricate relationships among real-world entities within a structured *** framework facilitates a transformation in information retrieval,transitioning it from mere string matching to far more sophisticated entity *** this transformative process,the advancement of artificial intelligence and intelligent information services is ***,the role ofmachine learningmethod in the construction of KG is important,and these techniques have already achieved initial *** article embarks on a comprehensive journey through the last strides in the field of KG via machine *** a profound amalgamation of cutting-edge research in machine learning,this article undertakes a systematical exploration of KG construction methods in three distinct phases:entity learning,ontology learning,and knowledge ***,a meticulous dissection of machine learningdriven algorithms is conducted,spotlighting their contributions to critical facets such as entity extraction,relation extraction,entity linking,and link ***,this article also provides an analysis of the unresolved challenges and emerging trajectories that beckon within the expansive application of machine learning-fueled,large-scale KG construction.

关键词： Knowledge graph(KG) semantic network relation extraction entity linking knowledge reasoning

Lightweight Dual‑Functional Segregated Nanocomposite Foams for Integrated Infrared Stealth and Absorption‑Dominant Electromagnetic Interference Shielding

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Nano-micro Letters 2024年第11期16卷 38-55页

作者： Zhonglei ma Ruochu Jiang Jiayao Jing Songlei Kang Li ma Kefan Zhang Junxian Li Yu Zhang Jianbin Qin Shuhuan Yun Guangcheng Zhang mOE Key Laboratory of material Physics and Chemistry Under Extraordinary Conditions Shaanxi Key Laboratory of Macromolecular Science and TechnologySchool of Chemistry and Chemical EngineeringNorthwestern Polytechnical UniversityXi’an 710072People’s Republic of China College of Chemistry and Chemical Engineering Key Laboratory of Auxiliary Chemistry and Technology for Chemical IndustryMinistry of EducationShaanxi University of Science and TechnologyXi’an 710072People’s Republic of China Department of mechanical and Industrial Engineering University of Toronto5 King’s College RoadTorontoON M5S 3G8Canada Chongqing Innovation Center Northwestern Polytechnical UniversityChongqing 401135People’s Republic of China

Lightweight infrared stealth and absorption-dominant electromagnetic interference(EmI)shielding materials are highly desirable in areas of aerospace,weapons,military and wearable ***,lightweight and high-efficiency dual-functional segregated nanocomposite foams with microcellular structures are developed for integrated infrared stealth and absorption-dominant EmI shielding via the efficient and scalable supercritical CO_(2)(SC-CO_(2))foaming combined with hydrogen bonding assembly and compression molding *** obtained lightweight segregated nanocomposite foams exhibit superior infrared stealth performances benefitting from the synergistic effect of highly effective thermal insulation and low infrared emissivity,and outstanding absorption-dominant EmI shielding performances attributed to the synchronous construction of microcellular structures and segregated ***,the segregated nanocomposite foams present a large radiation temperature reduction of 70.2℃ at the object temperature of 100℃,and a significantly improved Em wave absorptivity/reflectivity(A/R)ratio of 2.15 at an ultralow Ti_(3)C_(2)T_(x) content of 1.7 vol%.moreover,the segregated nanocomposite foams exhibit outstanding working reliability and stability upon dynamic compression *** results demonstrate that the lightweight and high-efficiency dual-functional segregated nanocomposite foams have excellent potentials for infrared stealth and absorption-dominant EmI shielding applications in aerospace,weapons,military and wearable electronics.

关键词： Segregated nanocomposite foams microcellular structures Infrared stealth EmI shielding Low infrared emissivity

Recommendation method for Contrastive Enhancement of Neighborhood Information

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Computers, materials & Continua 2024年第1期78卷 453-472页

作者： Hairong Wang Beijing Zhou Lisi Zhang He ma School of Computer Science and Engineering North Minzu UniversityNingxia750021China

Knowledge graph can assist in improving recommendation performance and is widely applied in various person-alized recommendation ***,existing knowledge-aware recommendation methods face challenges such as weak user-item interaction supervisory signals and noise in the knowledge *** tackle these issues,this paper proposes a neighbor information contrast-enhanced recommendation method by adding subtle noise to construct contrast views and employing contrastive learning to strengthen supervisory signals and reduce knowledge ***,first,this paper adopts heterogeneous propagation and knowledge-aware attention networks to obtain multi-order neighbor embedding of users and items,mining the high-order neighbor informa-tion of users and ***,in the neighbor information,this paper introduces weak noise following a uniform distribution to construct neighbor contrast views,effectively reducing the time overhead of view *** paper then performs contrastive learning between neighbor views to promote the uniformity of view information,adjusting the neighbor structure,and achieving the goal of reducing the knowledge noise in the knowledge ***,this paper introduces multi-task learning to mitigate the problem of weak supervisory *** validate the effectiveness of our method,experiments are conducted on themovieLens-1m,movieLens-20m,Book-Crossing,and Last-Fm *** results showthat compared to the best baselines,our method shows significant improvements in AUC and F1.

关键词： Contrastive learning knowledge graph recommendation method