检索结果-南通市图书馆

Discussion on the Neoproterozoic glaciations in the South China Block and their related paleolatitudes

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2009年第10期54卷 1797-1800页

作者： ZHANG QiRui CHU xuelei feng LianJun State Key Laboratory of Lithospheric Evolution Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029China

The Kaigas, Sturtian, Marinoan, and Gaskiers glaciations are widely recognized in Neoproterozoic. However, in the South China Block only the Jiangkou (Sturtian) and Nantuo (Marinoan) are symbolized by sedimentary records. The Kaigas, recorded by isotopic and chemical proxies, exhibited likely the nature of cold paleoclimate with local mountain glaciation. The correlation of the Doushantuo Formation with the Gaskiers is indicated by the carbon isotope excursion and the dated age from the interval, however the South China Block was then under non-glacial weather. With no paleomagnetic data, the position of the South China Block during the Sturtian glaciation cannot be determined. The paleolatitudes of the South China Block during the Kaigas and Nantuo glaciations are intermediate, even though the Nantuo was once rendered erratically deduced equatorial. In fact, the paleolatitudes of the South China Block during the Neoproterozoic glaciations are all likely at about 30°―40°.

关键词：冰期气候新元古代中国碳同位素古地磁数据沉积记录寒冷气候时间间隔

A review on the transformation of birnessite in the environment:Implication for the stabilization of heavy metals

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2024年第5期139卷 496-515页

作者： Miao Shi Qingzhu Li Qingwei Wang xuelei Yan Bensheng Li Linhai feng Chao Wu Rongrong Qiu Hongkai Zhang Zhihui Yang Weichun Yang Qi Liao Liyuan Chai School of Metallurgy and Environment Central South UniversityChangsha 410083China National Engineering Research Centre for Control and Treatment ofHeavy Metal Pollution Central South UniversityChangsha 410083China Water Pollution Control Technology Key Lab of Hunan Province Changsha 410083China

Birnessite is ubiquitous in the natural environment where heavy metals are retained and easily *** surface properties and structure of birnessite change with the changes in external environmental conditions,which also affects the fate of heavy *** the effect and mechanism of the birnessite phase transition process on heavy metals is the key to taking effective measures to prevent and control heavy metal ***,the four transformation pathways of birnessite are summarized first in this ***,the relationship between transformation pathways and environmental conditions is *** relevant environmental conditions include abiotic(e.g.,co-existing ions,pH,oxygen pressure,temperature,electric field,light,aging,pressure)and biotic factors(e.g.,microorganisms,biomolecules).The phase transformation is achieved by the key intermediate of Mn(Ⅲ)through interlayer-condensation,folding,neutralizationdisproportionation,and dissolution-recrystallization *** AOS(average oxidation state)of Mn and interlayer spacing are closely correlated with the phase transformation of *** but not least,the mechanisms of heavy metals immobilization in the transformation process of birnessite are summed *** involve isomorphous substitution,redox,complexation,hydration/dehydration,*** transformation of birnessite and its implication on heavy metals will be helpful for understanding and predicting the behavior of heavy metals and the crucial phase of manganese oxides/hydroxides in natural and engineered environments.

关键词： Birnessite Transformation Heavy metals Pathways Mechanism

参数不确定性内声场分析的封闭区间有限元方法

在线全文

学校读者我要写书评

暂无评论

振动与冲击 2022年第18期41卷 25-32页

作者：向育佳史治宇冯雪磊南京航空航天大学航空学院机械结构力学及控制国家重点实验室南京210016

针对含有不确定但有界参数的内声场预测问题,主要的区间建模方法为逐单元的区间有限元法(EBE-IFEM)和区间摄动有限元法(IPFEM)。但由于IPFEM在级数展开时存在非保守近似的缺陷,EBE-IFEM在利用拉格朗日乘子法来约束扩增的节点自由度时增... 详细信息

针对含有不确定但有界参数的内声场预测问题,主要的区间建模方法为逐单元的区间有限元法(EBE-IFEM)和区间摄动有限元法(IPFEM)。但由于IPFEM在级数展开时存在非保守近似的缺陷,EBE-IFEM在利用拉格朗日乘子法来约束扩增的节点自由度时增加了内存消耗并降低了迭代计算效率,现有方法很难兼备保守的结果和高的计算效率。为此,提出了一种新的封闭区间有限元方法(Enclosing-IFEM),结合“混合节点-单元”(MNE)的组装策略来缩减自由度,该方法能够在满足结果保守性的前提下,提高求解效率。而且,Enclosing-IFEM的区间动力学方程可以直接转化为“并矢积”形式,解决了基于Sherrman-Morrison-Woodbury(S-M-W)级数的区间摄动有限元法(SMW-IPFEM)的动力学拓展问题。最后,将蒙特卡罗方法以及它的区间有限元方法作为参考解,通过两个数值算例验证了Enclosing-IFEM的计算精度和效率。

关键词：封闭区间有限元方法(Enclosing-IFEM) S-M-W级数不确定性声场分析不确定但有界参数

CoPt-Co hybrid supported on amino modified SiO2 nanospheres as a high performance catalyst for hydrogen generation from ammonia borane

在线全文

学校读者我要写书评

暂无评论

Progress in Natural Science:Materials International 2019年第1期29卷 1-9页

作者： Hongming Zhang Dandan Ke Lina Cheng xuelei feng Xuewei Hou Jin Wang Yuan Li Shumin Han Heibei Key Laboratory of Applied Chemistry School of Environmental and Chemical Engineering Yanshan University State Key Laboratory of Metastable Materials Science and Technology Yanshan University

CoPt-Co hybrids were successfully supported on amino modified SiOnanospheres by a chemical reduction method at a temperature of 278 *** solid carrier *** modified SiO,provides numerous anchoring sites for the metal nanoparticles(NPs)to improve the dispersion while reducing the size of metal *** supported NPs displayed a narrow particle size distribution on the SiOsurface with an average diameter of 12 *** XRD results alongside with the binary alloy phase diagram suggest that the resulted NPs are bimetallic,composed of CoPt and amorphous *** the prepared materials,the solid with the specific composition of SiO@PtCowas proved to be effective catalyst for ammonia borane(AB)hydrolysis in aqueous *** turnover frequency(TOF)value of the supported nanocatalyst was 25.59molmin·mol,almost twice as that of unsupported PtCoNPs while the activation energy was 37.05 kJ ***,the SiO@PtCocomposite manifested high catalytic activity even after five cycles of reuse.

关键词： CoPt-Co hybrid catalyst Hydrogen generation NH3·BH3 hydrolysis SiO2 nanospheres

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

直接辐射式扬声器系统的低频效率计算公式

应用声学 2022年第6期41卷 860-866页

作者：陈睿沈勇冯雪磊南京大学声学研究所近代声学教育部重点实验室南京210093

效率是扬声器系统的重要性能指标,然而常用的标称效率在低频范围并不适用。该文研究直接辐射式扬声器系统的低频效率,推导了基于TS参数的低频效率计算公式。针对封闭式扬声器系统和倒相式扬声器系统,开展实验验证,结果表明该文提出的计... 详细信息

效率是扬声器系统的重要性能指标,然而常用的标称效率在低频范围并不适用。该文研究直接辐射式扬声器系统的低频效率,推导了基于TS参数的低频效率计算公式。针对封闭式扬声器系统和倒相式扬声器系统,开展实验验证,结果表明该文提出的计算公式得到的低频效率与实验测量得到的低频效率较为相符。进一步对比分析低频效率和标称效率,结果表明低频效率能够适用于低频,能准确地展示扬声器系统参数对效率的影响。利用该文提出的计算公式,有助于进一步优化提升扬声器系统的低频效率。

关键词：扬声器系统效率直接辐射式扬声器系统效率提升

基于模态控制法的平板扬声器指向性控制算法研究

在线全文

学校读者我要写书评

暂无评论

南京大学学报（自然科学版） 2023年第6期59卷 1059-1068页

作者：卫文港程嘉正冯雪磊沈勇近代声学教育部重点实验室南京大学物理学院南京210023

平板扬声器使用激励器驱动薄板产生弯曲振动从而辐射声波,已在手机、电视机等设备中得到应用.模态控制法在平板扬声器的振动控制领域已有较为深入的研究,但尚未发现将其应用于平板扬声器指向性控制的研究先例.结合屏幕发声技术与空间声... 详细信息

平板扬声器使用激励器驱动薄板产生弯曲振动从而辐射声波,已在手机、电视机等设备中得到应用.模态控制法在平板扬声器的振动控制领域已有较为深入的研究,但尚未发现将其应用于平板扬声器指向性控制的研究先例.结合屏幕发声技术与空间声重放理论,创新性引入模态控制法实现平板扬声器指向性声场控制,首次推导出从动圈式激励器驱动电压到平板扬声器模态激励的频域传递函数公式.结合数值仿真,采用模态控制法对平板扬声器声辐射特性进行指向性控制.结果表明,使用模态控制法控制波束主瓣轴向和覆盖角的效果显著,指向性控制是实现定向发声的关键.

关键词：平板扬声器指向性控制模态控制法算法

Variations of sulfur and carbon isotopes in seawater during the Doushantuo stage in late Neoproterozoic

在线全文

学校读者我要写书评

暂无评论

Chinese Science Bulletin 2003年第13期48卷 1375-1380页

作者： ZHANG Tonggang, CHU xuelei, ZHANG Qirui, feng Lianjun & HUO Weiguo Key Lab of Mineral Resources Exploration and Research, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China Key Lab. of Mineral Resources Exploration and Research Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China

Successive analyses of sulfur and carbon isotopic compositions of carbonates strata in the Doushantuo Formation in the Yangtze area were accomplished through a method of extracting trace sulfate from carbonates. Sulfur and carbon isotopic compositions of coeval seawater were estimated from the samples that show the least diagenetic alteration. A high-resolution age curve of sulfur isotopes in seawater sulfates was obtained in the Doushantuo stage, which reflects the trend of variation in seawater sulfur isotopes after the Neoproterozoic snowball Earth event. Similar characteristics of variation in carbon isotopes were observed in the coeval carbonates. A large positive d 34S excursion over +20?occurs in ancient seawater sulfates in the early Doushantuo stage. Simultaneously, the d 13C values in ancient seawater carbonates exhibit a positive excursion up to 10. The maximum d 34S and d 13C values are +46.4 and +6.9? respectively. In the middle Doushantuo stage, the range of variation in d 34S values of seawater is relatively narrow, but d 13C values are quite high. Then, d 34S values of seawater become oscillating, and the same occurs in d 13C values. Negative excursions in d 34S and d 13C values occur simultaneously at the end of the Doushantuo stage, and the minimum d 34S and d 13C values dropped down to -10.1 and -5.7? respectively. The characteristics of variations in the sulfur and carbon isotopes of ancient seawater imply strong changes in oceanic environment that became beneficial to inhabitation and propagation of organism. The organic productivity and burial rate of organic carbon once reached a quite high level during the Doushantuo stage. However, the state of environment became unstable after the global glaciation. The global climate and environment possibly were fluctuating and reiterating. The negative excursions in d 34S and d 13C values occurring at the end of the Doushantuo stage may represent a global event, which might be related to oxidation of dee

关键词：硫碳同位素分馏新元古代成岩作用

在线全文

学校读者我要写书评

暂无评论

镁合金超疏水环氧复合涂层的制备与性能

材料工程 2022年第8期50卷 124-132页

作者：夏先朝冯学磊孙京丽聂敬敬庞松袁勇董泽华上海航天精密机械研究所上海201600 华中科技大学化学与化工学院武汉430074 宁东能源化工基地管委会银川750411

传统的超疏水表面的制备过程比较复杂,机械稳定性差,这严重制约了超疏水表面的实际应用。采用“黏合剂+纳米粒子”的方法,在镁合金表面制备一种无氟、持久稳定的超疏水环氧复合涂层。接触角测试结果表明,复合涂层的接触角最高可达160.2... 详细信息

传统的超疏水表面的制备过程比较复杂,机械稳定性差,这严重制约了超疏水表面的实际应用。采用“黏合剂+纳米粒子”的方法,在镁合金表面制备一种无氟、持久稳定的超疏水环氧复合涂层。接触角测试结果表明,复合涂层的接触角最高可达160.2°,且在3.5%(质量分数)NaCl溶液中浸泡30天后,接触角仍然高达103°;EIS结果表明,在5个加速老化循环周期后,复合涂层的|Z|_(0.01 Hz)仍高于10^(9)Ω·cm^(2),展现出优异的耐盐雾性能和耐蚀性能;摩擦磨损实验结果显示,在19.6 N的载荷下机械摩擦8 h后,复合涂层的|Z|_(0.01 Hz)高达1.84×10^(9)Ω·cm^(2)。通过“空气垫”的屏障作用,复合涂层能够为镁合金提供高效且持久的腐蚀防护,“黏合剂+纳米粒子”策略为超疏水涂层的制备提供了新的思路。

关键词：镁合金超疏水涂层腐蚀防护环氧涂层

维普期刊数据库博看期刊

杜定友在交通大学图书馆建设中的贡献成就与精神内涵剖析——以交通大学图书馆馆务会议记录等档案资料为据

在线全文

学校读者我要写书评

暂无评论

大学图书馆学报 2024年第3期42卷 82-89页

作者：杨峰张雪蕾王懿松毛瑞江西安交通大学图书馆陕西西安710049

杜定友先生作为中国近代图书馆事业的先驱,其在图书馆领域的卓越贡献与所展现出的图书馆精神内涵,具有深远的历史意义和现实启示。文章以西安交通大学档案馆所珍藏的1930至1936年间图书馆馆务会议记录等档案资料为据,深入梳理了他在交... 详细信息

杜定友先生作为中国近代图书馆事业的先驱,其在图书馆领域的卓越贡献与所展现出的图书馆精神内涵,具有深远的历史意义和现实启示。文章以西安交通大学档案馆所珍藏的1930至1936年间图书馆馆务会议记录等档案资料为据,深入梳理了他在交通大学图书馆任职期间于馆务行政管理方面的实践举措,剖析了他在图书馆管理、人才培养、服务创新等方面的贡献成就。史料折射出杜定友先生对图书馆事业执着奉献的精神,彰显出其在学术研究、人才培养、读者至上等图书馆精神理念方面的前瞻性思考。

关键词：杜定友交通大学图书馆图书馆馆务会议图书馆精神

维普期刊数据库博看期刊