检索结果-南通市图书馆

Quantitative reconstruction of salinity and precipitation changes in Central Asia over the past 3200 years using diatom and pollen records of lacustrine sediment in Aibi Lake of SW Junggar Basin

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

Journal of Earth Science 2025年

作者： Long Pan Guoqiang Li Xiaoyan Wang Ming Jin Xinrong he Luo Qin Zhong Wang Wenwei Zhao Chunzhu Chen Yuanlu Liu Jin Yang Lele Shu Key Laboratory of Western China's Environmental Systems (Ministry of Education)， College of Earth and Environmental Sciences， Lanzhou University College of Earth Sciences， Chengdu University of Technology School of Geographic Science， Nantong University Key Laboratory of Land Surface Process and Climate Change in Cold and Arid Regions， Northwest Institute of Eco-Environment and Resources， Chinese Academy of Sciences

The response of lake environments in arid Central Asia to climate change during the Late Holocene over the centennial to millennial timescales remains contentious. The reason that primarily paleoenvironmental proxies interpreting diverse and the scarcity of accurate quantitative reconstruction records. In this study， we employed diatoms and pollen records from lacustrine sediment in the Aibi Lake of SW Junggar Basin to quantitatively reconstruct salinity and watershed precipitation amounts while exploring the associated forcing mechanism. The results indicate that Aibi Lake salinity varied between 2 g/L and 47 g/L during the Late Holocene period， indicating a generally brackish environment， and corresponding to prevailing Tryblionella granulata diatom in the lake basin. Westerly-dominated annual precipitation varied between 250 mm and 320 mm during the Late Holocene period in the basin， exhibiting a generally semi-arid environment and prevailing desert steppe vegetation. The Aibi Lake has a low salinity of average value of ～15 g/L. It exhibits elevated precipitation (average value of ～280 mm) during the periods of the Roman Warm Period (2900-1990 cal yr BP)， Dark Age Cold Period (1570-1140 cal yr BP)， and Little Ice Age (590-120 cal yr BP). The reconstructed precipitation and salinity exhibit a periodicity of ～200 years， which is consistent with the cycle of phase changes of the North Atlantic Oscillation (NAO) and Total Solar Irradiance (TSI). This correlation suggests that variations in NOA and TSI significantly influence the precipitation and salinity changes in Central Asia over centennial to millennial timescales.

关键词：

The SPECTRAL RADIUS OF UNIFORM HYPERGRAPH DETERMINED BY The SIGNLESS LAPLACIAN MATRIX

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

数学杂志 2025年第1期45卷 1-12页

作者： he Fang-guo College of Mathematics and Statistics Huanggang Normal UniversityHuBei 438000

This paper studies the problem of the spectral radius of the uniform hypergraph determined by the signless Laplacian *** upper bound of the spectral radius of a uniform hypergraph is obtained by using Rayleigh principle and the perturbation of the spectral radius under moving the edge operation,and the extremal hypergraphs are characterized for both supertree and unicyclic *** spectral radius of the graph is generalized.

关键词： spectral radius uniform hypergraph Signless Laplasian matrix

同方期刊数据库

Influence of Setting Accelerating Agents on Properties of Colloidal Alumina Bonded Corundum Castables

在线全文

学校读者我要写书评

暂无评论

China's Refractories 2020年第1期29卷 31-35页

作者： ZHANG Xiaohui YU Xingguo WANG Baoyu ZHU boquan Sinosteel Luoyang Institute of Refractories Research Co. Ltd.Luoyang 471039China Jiangsu Chianaref Refractory Co. Ltd.Yixing 214266China The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081China

In order to improve the flow ability and early-stage strength of colloidal alumina bonded corundum castables,the colloidal alumina with 20%of solid content was used as the binder,and tabular corundum aggregates and fines,and active alumina micropowder CL370 as the main starting *** of setting accelerating agents(magnesia fines and sodium meta-aluminate)on the linear change rate,the modulus of rupture and the microstructure of corundum castables after different heat-treatments were *** results show(1)cement bonded corundum castables have the highest modulus of rupture after 24 h of demolding,and colloidal alumina bonded corundum castables have the lowest one;both magnesia fines and sodium meta-aluminate can improve the strength after 24 h of demolding;(2)after firing at 1000℃for 3 h,the modulus of rupture of all specimens decreases,even lower than that after 24 h of demolding;(3)after firing at 1600℃for 3 h,the castable specimen added with 0.1 mass%magnesia fines has the highest modulus of rupture;the tabular phases appear interwovenly in the specimen;(4)taking the comprehensive properties into account,0.1 mass%of magnesia fines is appropriate,and the addition of sodium meta-aluminate shall be lower than 0.3%.

关键词： corundum colloidal alumina setting accelerating agent magnesia fines sodium meta-aluminate

拥有兄弟姐妹如何影响青少年的认知能力和主观幸福感?

在线全文

学校读者我要写书评

暂无评论

华东师范大学学报（教育科学版） 2025年第1期43卷 81-95页

作者：梁文艳何茜北京师范大学教育学部北京100875 北京师范大学首都教育经济研究基地北京100875

本研究对兄弟姐妹数量与青少年成长之间的关系进行了全面的理论探讨,并利用2010—2018年中国家庭追踪调查数据,为识别兄弟姐妹对青少年认知能力和主观幸福感的影响提供了微观证据。实证研究结果表明:拥有1个兄弟姐妹对青少年的主观幸福... 详细信息

本研究对兄弟姐妹数量与青少年成长之间的关系进行了全面的理论探讨,并利用2010—2018年中国家庭追踪调查数据,为识别兄弟姐妹对青少年认知能力和主观幸福感的影响提供了微观证据。实证研究结果表明:拥有1个兄弟姐妹对青少年的主观幸福感有积极影响,这种影响效应随年龄增长而加强,并且在成年后依旧保持稳定;拥有兄弟姐妹可能对青少年的数学类认知能力产生负向影响,这种影响主要体现在较低学段样本中,并随年龄增长逐渐消失。本研究为父母制定生育决策时更有效地开展成本收益分析提供了支持,也为缓解养育焦虑、完善生育政策以及促进人口可持续发展提供了政策启示。

关键词：资源稀释群聚理论同胞互动模型认知能力主观幸福感

Carbonization of Ni-doped Phenol Resin Under Various Conditions

同方期刊数据库博看期刊评论

在线全文

学校读者我要写书评

暂无评论

China's Refractories 2017年第2期26卷 25-30页

作者： WEI Guoping ZHU boquan LI Xiangcheng MA Zheng Zhejiang Zili Co. Ltd. The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and Technology

Ni-doped phenol resin was prepared with 1∶100 mass ratio of Ni（ NO_3）_2·6H_2O to thermosetting phenol resin to optimize the structure and properties of pyrolytic carbon derived from phenol resin and increase its carbon yield. The specimens were cured at 200 ℃ and carbonized under different atmospheres（ carbon-embedded atmosphere and Ar atmosphere） and at different temperatures（ 600,800,1000 and 1200 ℃） for3 h,respectively. The carbon yield was measured. Thermal decomposition characteristics of Ni-doped phenol resin,and the oxidation resistance,phase composition and microstructure of pyrolytic carbon were characterized by differential scanning calorimetry,X-ray diffraction,energy dispersive spectroscopy, scanning electron microscopy and transmission electron microscopy. The results show that the carbon yield of Ni-doped phenol resin carbonized at800 or 1 000 ℃ is increased significantly,compared with that without any dopants. The graphitization degree of pyrolytic carbon structure derived from Ni-doped phenol resin increases with the increase of carbonization temperature. The massive multi-wall carbon nanotubes of 50-100 nm in diameter and of micrometre scale in length are generated at 1000 ℃. Compared with the carbonembedded atmosphere,carbon nanotubes can be more easily generated in Ar atmosphere,resulting in higher carbon yield and degree of crystallinity of the pyrolyticcarbon derived from Ni-doped phenol resin. The oxidation resistance of the pyrolytic carbon derived from Ni-doped phenol resin at 1200 ℃ is improved significantly and its highest oxidation temperature is increased by about 84℃,compared with that from Ni free phenol resin.

关键词： phenol resin nickel-doping carboniza-tion pyrolytic carbon carbon nanotubes oxidation re-sistance

Influence of Dispersants on Flow Ability of Colloidal Alumina Bonded Corundum Castables

在线全文

学校读者我要写书评

暂无评论

China's Refractories 2019年第4期28卷 26-30页

In order to make corundum castables satisfy more severe service conditions in high temperature industries,colloidal alumina due to the same main component with corundum castables was introduced for a pure binding *** influence of three dispersants(citric acid,FS10 and urea)on the flow ability of colloidal alumina bonded corundum castables was researched to choose a suitable dispersant for solving the shaping *** order to further understand the influence of dispersants on the flow ability and the mechanism,the rheological property and Zeta potential value of the colloidal aluminadispersant system and the matrix-colloidal alumina-urea-water system were *** results show the castables added with the urea have the best flow ability,and the appropriate addition of the urea is 0.5%.

关键词： corundum castables colloidal alumina dispersant citric acid FS10 urea rheological property Zeta potential

Research on Two-stage Voltage and Reactive Power Optimization Coordinated Control Method Considering Flexible On-load Tap Changer

在线全文

学校读者我要写书评

暂无评论

Dianwang Jishu/Power System Technology 2025年第1期49卷 272-283页

作者： Li, Jiaming Huo, Qunhai Yin, Jingyuan Lu, Hao Zhou, Jing Zhu, Meisheng he, Wei Dong, Hongwei Institute of Electrical Engineering Chinese Academy of Sciences Haidian District Beijing 100192 China School of Electronic Electrical and Communication Engineering University of Chinese Academy of Sciences Shijingshan District Beijing 100049 China Shanghai Jiguang Polytechnic College Baoshan District Shanghai 201901 China Three Gorges Electric Power Co. Ltd. Hubei Province Wuhan 430000 China

With the large-scale integration of distributed photovoltaic (DPV) in the distribution network, voltage exceeding limits and fluctuations are becoming increasingly severe. The voltage and reactive power optimization and coordination control method considering new power quality management devices needs to be further improved to adapt to the new changes in the power grid. This article considers the power quality regulation effect of the new flexible on-load tap changer (OLTC) and proposes a two-stage voltage and reactive power optimization coordinated control method. The first stage is the day before hour level scheduling stage. Based on distributed photovoltaic and load prediction data, the active output results of DPV and the switching results of flexible OLTC taps and capacitor banks are obtained through power flow calculation and iterative optimization. The second stage is the minute-level reactive power optimization stage. Based on the first stage, considering the reactive power output characteristics of flexible OLTC and DPV, adjusting the reactive power output of the equipment while correcting the capacitor bank switching combination in the first stage, further reducing the maximum voltage deviation of each node and making the distribution network voltage distribution more reasonable. An IEEE33 node distribution system simulation model is built in the paper. The proposed two-stage voltage and reactive power optimization coordination control method considering flexible OLTC can improve the DPV absorption level by 9.29% based on the conventional economic optimal goal of 88.07%, while meeting the requirement that the voltage deviation of the entire node is less than 0.1pu During the entire period, the overall economic efficiency improved by 7.8%. The results demonstrate the rationality and effectiveness of the proposed method. © 2025 Power System Technology Press. All rights reserved.

关键词： Quality management

Sintering Densification of Boron Carbide Materials and Their Research Progress

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

China's Refractories 2023年第4期32卷 22-27页

作者： ZOU Xin CheN Ping'an XU Guangping LI Xiangcheng ZHU Yingli ZHU boquan The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan 430081China Jiangsu Zhonglei Energy-saving Technology Development Co. Ltd.Dongtai 224200China

Boron carbide(B_(4)C)has excellent high-temperature oxidation resistance,high hardness,low relative density,high melting point and excellent abrasive resistance,which is widely used in fields such as refractories,wear-resistant materials and lightweight protective *** research progress and application of B_(4)C materials in China and overseas in recent years were *** influences of sintering processes(pressureless sintering,hot-pressing sintering,hot isostatic pressing sintering,spark plasma sintering and microwave sintering)and sintering additives(simple substances,oxides and carbides)on the B_(4)C densification were *** development of B_(4)C materials was prospected.

关键词： boron carbide refractories densification preparation method sintering additive research progress

Influences of Al and Si Powders on Microstructure and Hot Mechanical Properties of Al_2O_3-C Slide Plates

在线全文

学校读者我要写书评

暂无评论

China's Refractories 2014年第3期23卷 31-34页

作者： ZHAO Fei ZHU boquan LI Xiangcheng ZHU Yuenan The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and Technology

The basic formulation of Al2O3- C slide plates was65%（ in mass,the same hereinafter） white fused corundum particles,25% white fused corundum fines,6% active α-Al2O3 micropowder,4% carbon black and flake graphite, and additional 4% phenolic *** on this formulation,3% Al powder,3% Si powder,and 3% Al ＋ 3% Si powder were used to substitute equivalent white corundum fines to improve the hot mechanical properties of Al2O3- C slide plates. The specimens with dimensions of 140 mm × 25 mm × 25 mm were pressed at 150 MPa,dried at 200 ℃ for 24 h,and hot treated at 1 400 ℃ for 3 h in carbon embedded condition. Then hot modulus of rupture and thermal shock resistance of the specimens were tested and the phase compositions and microstructure were analyzed. The results show that specimen with 3% Al powder has the higher hot modulus of rupture but lower residual modulus of rupture after thermal shock than the specimen with3% Si powder; the specimen with 3% Al ＋ 3% Si powders exhibits the highest hot modulus of rupture and the best thermal shock resistance; the change of mechanical property is closely related with the in-situ formed nonoxides： AlN in the form of bars is formed in specimens with Al powder; fibrous SiC whiskers are formed in specimens with Si powder; in the specimens with both Al and Sipowders,besides AlN and SiC whiskers,hexagonal tabular SiAlON is in-situ synthesized,which interlocks with each other.

关键词： aluminum powder silicon powder alumi-na - carbon slide plate hot mechanical property mi-crostructure