检索结果-南通市图书馆

Polymer-to-Monomers Chemically Recyclable Poly(imide-imine)Plastics with Extreme-Condition Resistance and Flame Retardancy

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10期42卷 1525-1535,I0012页

作者： zhen-yu Wang Xiao-Kong Liu State Key Laboratory of Supramolecular Structure and Materials College of ChemistryJilin UniversityChangchun130012China

Polyimides are a family of high-tech plastics that have irreplaceable applications in the fields of aerospace,defense,and opto-electronics,but polyimides are difficult to be reprocessed and recycled at the end of their service life,resulting in a significant waste of ***,it is of great significance to develop recyclable polyimides with comparable properties to the commercial ***,we report a novel polymer-to-monomers chemically recyclable poly(imide-imine)(PtM-CR-PII)plastic,synthesized by cross-linking the amine-terminated aromatic bisimide monomer and the hexa-vanillin terminated cyclophosphazene monomer via dynamic imine *** PtM-CR-PII plastic exhibits comparable mechanical and thermal properties as well as chemical stability to the commercial *** PtM-CR-PII plastic possesses a high Young’s modulus of≈3.2 GPa and a tensile strength as high as≈108 MPa,which also exhibits high thermal stability with a glass transition temperature of≈220℃.Moreover,the PtM-CR-PII plastic exhibits outstanding waterproofness,acid/alkali-resistance,and solvent-resistance,its appearance and mechanical properties can be well maintained after long-term soaking in water,highly concentrated acid and base,and various organic ***,the cyclophosphazene moieties endow the PtM-CR-PII plastic with excellent flame *** PtM-CR-PII plastic exhibits the highest UL-94 flame-retarding rating of V-0 and a limiting oxygen index(LOI)value of 45.5%.Importantly,the PtM-CR-PII plastic can be depolymerized in an organic solvents-acid mixture medium at room temperature,allowing easy separation and recovery of both monomers in high *** recovered pure monomers can be used to regenerate new PtM-CR-PII plastics,enabling sustainable polymer-monomers-polymer circulation.

关键词： Chemical recyclability Polyimides Polyimines Dynamic imine bonds Mechanical properties Chemical stability

First Passage Density of Brownian Motion with Two-sided Piecewise Linear Boundaries

在线全文

学校读者我要写书评

暂无评论

Acta Mathematica Sinica,English Series 2024年第6期40卷 1505-1520页

作者： zhen yu Mao Zai TIAN Center for Applied Statistics School of StatisticsRenmin University of ChinaBeijing 100872P.R.China School of Mathematics and Data Science Changji UniversityChangji 831100P.R.China

The first passage time has many applications in fields like finance,econometrics,statistics,and ***,explicit formulas for the first passage density have only been obtained for a few *** paper derives an explicit formula for the first passage density of Brownian motion with twosided piecewise continuous boundaries which may have some points of *** are used to obtain a simplified formula for estimating the first passage ***,the results are also generalized to the case of two-sided general nonlinear *** can be easily carried out with Monte Carlo method and it is demonstrated for several typical two-sided boundaries that the proposed approximation method offers a highly accurate approximation of first passage density.

关键词： Boundary non-crossing probability first density passage density two-sided piecewise continuous boundaries Brownian motion

The breaking of spin symmetry in the single-particle resonances in deformed nuclei

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第3期35卷 237-245页

作者： zhen-yu zheng Shou-Wan Chen Quan Liu School of Physics and Optoelectronic Engineering Anhui UniversityHefei 230601China

The exploration of spin symmetry (SS) in nuclear physics has been instrumental in identifying atomic nucleus *** this study,we solve the Dirac equation from the relativistic mean field (RMF) in complex momentum *** investigated SS and its breaking in single-particle resonant states within deformed nuclei,with a focus on the illustrative *** was the initial discovery of a resonant spin doublet in a deformed nucleus,with the expectation of the SS approaching the continuum *** increasing single-particle energy,the splitting of the resonant spin doublets widened *** escalating splitting implies diminishing adherence to the SS,indicating a departure from the expected behavior as the energy levels *** also analyzed the width of the resonant states,showing that lower orbital angular momentum resonances possess shorter decay times and that SS is preserved within broad resonant doublets,as opposed to narrow resonant *** the radial density of the upper components for the bound-state and resonant-state doublets,it becomes evident that while SS is well-preserved in the bound states,it deteriorates in the resonant *** impact of nuclear deformation (β_(2)) on SS was examined,demonstrating that an increase in β_(2) resulted in higher energy and width splitting in the resonant spin doublets,which is attributed to increased component ***,the sensitivity of spin doublets to various potential parameters such as surface diffuseness (a),radius (R),and depth (Σ0) is discussed,emphasizing the role of these parameters in *** study provides valuable insights into the behavior of spin doublets in deformed nuclei and their interplay with the nuclear structure,thereby advancing our understanding of SS in the resonance state.

关键词： Spin symmetry Resonant states Deformed nuclei Complex-momentum representation

New Vacuum Solar Telescope Achieves Narrowband Infrared Solar Imaging Observation at He I 10830 A

在线全文

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2024年第5期24卷 76-84页

作者： Wei-Jie Meng Fang-yu Xu zhen-yu Jin yunnan Observatories Chinese Academy of SciencesKunming 650011China yunnan Key Laboratory of Solar Physics and Space Science Kunming 650216China University of Chinese Academy of Sciences Beijing 100049China

The near-infrared imaging channel constitutes a crucial component of the multichannel high-resolution imaging system of the New Vacuum Solar Telescope(NVST). We have successfully achieved high-resolution, narrowband imaging of the chromosphere using He I 10830 A triplet within this channel, which significantly enhances the imaging observation capabilities of NVST. This paper provides a concise overview of the optical system associated with the near-infrared imaging channel, detailing data processing procedures and presenting several observed images. Leveraging a high-resolution image reconstruction algorithm, we were able to generate a narrowband image near the diffraction limit at 10830 A with a temporal resolution of less than 10 s.

关键词： instrumentation detectors-instrumentation high angular resolution-Sun chromosphere-Sun infrared

Narrative review of latest research progress about robotic percutaneous coronary intervention

在线全文

学校读者我要写书评

暂无评论

Journal of Geriatric Cardiology 2024年第8期21卷 816-825页

作者： zhen-yu LIU Guang-Yao ZHAI Department of Clinical Medicine Beijing Luhe HospitalCapital Medical UniversityBeijingChina Department of Cardiology Beijing Luhe HospitalCapital Medical UniversityBeijingChina

Robotic percutaneous coronary intervention(R-PCI)is a novel technology in which operators can manipulate guidewires and catheter devices in interventional *** approach provides great benefits to interventional cardiologists in terms of reducing both radiation exposure and orthopedic *** large,high-quality cohort studies have confirmed the short-term safety and high technical success rate of ***,randomized long-term data are still needed before adopting them as part of standard coronary ***,tele-stenting for complex coronary lesions has significant potential for *** need to overcome the present relevant challenges for its application such as inherent delays,bedside care for unstable patients from R-PCIs to manual PCIs(M-PCIs),incompatibility for a thrombus aspiration catheter and heavily calcified *** is a great future in laboratory workflow teams,3D-printed anatomical models and multiple joint collaborative control *** narrative review summarizes the latest developments in R-PCI,with a focus on developments in robotic technology,and discusses the current and future potential use of R-PCI in clinical practice globally.

关键词： coronary injuries unstable

Research on the mechanism of the two-dimensional ultrasonic surface burnishing process to enhance the wear resistance for aluminum alloy

在线全文

学校读者我要写书评

暂无评论

Friction 2024年第3期12卷 490-509页

作者： zhen-yu ZHOU Qiu-Yang zhenG yu LI Cong DING Guang-Jian PENG Zhong-yu PIAO College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310023China Key Laboratory of Special Purpose Equipment and Advanced Processing Technology Ministry of Education and Zhejiang ProvinceZhejiang University of TechnologyHangzhou 310014China

The gradient nanostructure is machined on the aluminum(Al)alloy by the two-dimensional ultrasonic surface burnishing process(2D-USBP).The mechanism of why the gradient nanostructure enhances wear resistance is *** mechanical properties and microstructure characterization for the gradient nanostructure are performed by operating a nanoindenter,transmission electron microscopy(TEM),and electron backscattered diffraction(EBSD).Dry wear tests are performed on the samples before and after machining to evaluate the wear resistance and *** effect of the gradient nanostructure on the wear resistance is explored by developing the crystal plasticity(CP)finite element and molecular dynamics(MD)*** characterization results show that the 2D-USBP sample prepared a gradient structure of~600μm thick on the aluminum surface,increasing the surface hardness from 1.13 to 1.71 GPa and reducing the elastic modulus from 78.84 to 70.14 *** optimization of the surface microstructure and the increase of the mechanical properties effectively enhance the wear resistance of the sample,with 41.20%,39.07%,and 54.58% of the wear scar areas for the 2D-USBP treated samples to the original samples under 5,10,and 15 N loads,*** gradient nanostructure hinders the slip of dislocations inside the sample during the wear process and reduces the size and scope of plastic deformation;meanwhile,the resistance to deformation,adhesion,and crack initiation and propagation of the sample surface is improved,resulting in enhanced wear resistance.

关键词： structural superlubricity lattice registry elastic deformation strained solitons crystal plasticity molecular dynamics simulations

Effects of Ocean Acidification on Nitrogen Metabolism of Skeletonema costatum

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 Ocean University of China 2024年第5期23卷 1359-1370页

作者： WANG Shuxing MI Tiezhu zhen yu ZHU Jianbin Key Laboratory of Marine Environment and Ecology Ministry of EducationCollege of Environmental Science and EngineeringOcean University of ChinaQingdao 266100China Laboratory for Marine Ecology and Environmental Science Qingdao Marine Science and Technology CenterQingdao 266237China Frontiers Science Center for Deep Ocean Multispheres and Earth System Ocean University of ChinaQingdao 266100China

Ocean acidification(OA),caused by the rising concentration of atmospheric CO_(2),leads to changes in the marine carbonate ***,in turn,affects the physiological processes of *** response to increased pCO_(2) levels,marine microalgae modulate their physiological responses to meet their energy and metabolic *** metabolism is a critical metabolic pathway,directly affecting the growth and reproductive capacity of marine *** the molecular mechanisms that regulate nitrogen metabolism in microalgae under OA conditions is therefore *** study aimed to investi-gate how OA affects the expression profiles of key genes in the nitrogen metabolic pathway of the marine diatom Skeletonema *** findings indicate that OA upregulates key genes involved in the nitrogen metabolic pathway,specifically those related to nitrate assimilation and glutamate ***,pCO_(2) has been identified as the predominant factor affecting the expression of these genes,with a more significant impact than pH variations in *** research not only advances our understanding of the adaptive mechanisms of *** in response to OA but also provides essential data for predicting the ecological consequences of OA on marine diatoms.

关键词： Skeletonema costatum ocean acidification nitrogen metabolism gene expression transcriptome

A late Carboniferous transition from subduction to collision:Tectonosedimentary evidence from southern Junggar,NW China

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2024年第3期15卷 166-179页

作者： Shuoqin Hou Di Li Dengfa He yu Lu yu zhen Hao Yang Dan Fan Key Laboratory of Marine Reservoir Evolution and Hydrocarbon Accumulation Mechanism the Ministry of Educationand School of Energy ResourcesChina University of Geosciences(Beijing)Beijing 100083China

The Carboniferous to Permian tectono-sedimentary evolution of the southern Junggar area brings new insights into understanding the subduction-collision processes in the northern Tianshan *** geophysics,geochemistry,and geochronology approaches,this study investigates the Carboniferous-Permian strata in the southern Junggar *** results have revealed three distinct tectono-stratigraphic evolutionary stages,each marked by a distinctive volcano-sedimentary *** Early Carboniferous strata suggest intense volcanic activities in the southern Junggar *** the Late Carboniferous,the southern Junggar Basin was controlled by normal faulting in an extensional setting,receiving sedimentary inputs from the Junggar *** Lower Permian,unconformably overlying the Upper Carboniferous,was shaped by an extensional regime and is comprised by volcano-clastic sequences that received detritus from the Yili-Central Tianshan *** findings indicate that a Late Carboniferous forearc basin developed in the southern Junggar area,and it evolved into a post-collisional rift in the Early *** period marked a dynamic shift from bidirectional subduction(rollback)to the detachment of the North Tianshan oceanic *** propose that the collision between the YiliCentral Tianshan block and the Junggar terrane,along with the closure of the North Tianshan Ocean,likely occurred in the Late Carboniferous(ca.306-303 Ma).

关键词： Tectono-sedimentary evolution Tectonic transition Carboniferous-Permian Junggar Basin North Tianshan Ocean

Climatic impacts induced by winter wheat irrigation over North China simulated by the nonhydrostatic RegCM4.7

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Advances in Climate Change Research 2024年第2期15卷 197-210页

作者： Jia WU zhen-yu HAN Xue-Jie GAO zheng-Jia LIU National Climate Centre China Meteorological AdministrationBeijing 100081China Key Laboratory for Climate Studies China Meteorological AdministrationBeijing 100081China Climate Change Research Center Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters Nanjing University of Information Science and TechnologyNanjing 210044China Institute of Geographic Sciences and Natural Resources Research Chinese Academy of SciencesBeijing 100101China

Quantification of the impact of winter wheat irrigation on the climate and the occurrence of extreme climatic events over North China is crucial for regional adaptation *** related studies mainly focused on the impact on surface processes;however,few focused on the effects of extreme events using high-resolution nonhydrostatic regional climate ***,the 9-km-resolution nonhydrostatic RegCM4.7 was coupled with a crop irrigation scheme and an updated winter wheat irrigation dataset to better simulate irrigation *** experiments were conducted with and without winter wheat irrigation to isolate the effects of *** showed that irrigation simulation reduces the model biases in temperature,precipitation,latent heat flux,soil moisture,sensitive heat flux,and top-layer soil ***,it also reduces the bias and increases the correlation with observations obtained in irrigated areas,especially in summer,indicating better representation of irrigation *** wheat irrigation tends to cause substantial cooling of the local surface maximum,minimum,and mean air temperatures(by-1.68,-0.34,and-0.79℃,respectively)over irrigated areas of North China,with the largest changes observed in relation to maximum ***,precipitation is found to increase during spring and summer,which is strongly related to water vapor transport in the lower levels of the *** analyses indicated that the number of annual mean hot days decrease(-13.9 d),whereas the number of both comfort days(+10.2 d)and rainy days(days with total precipitation greater than 1 mm:+6.6 d)increase over irrigated areas,demonstrating beneficial feedback to human perception and ***,although the heat wave risk increases(number of annual mean heat wave days:+5.8 d),the impact is limited to small areas within irrigated ***,no notable change was found in terms of heavy rainfall events and precipitation intensity

关键词： Nonhydrostatic regional climate model Irrigation effect Extreme events North China