检索结果-南通市图书馆

盐度和淹水频率对上海崇明东滩盐沼湿地近海区域土壤种子库动态的影响

在线全文

学校读者我要写书评

暂无评论

植物资源与环境学报 2025年第1期34卷 11-20,32页

作者：王莹李德志陈婧贾静 RASOOL Samreen Ghulam 华东师范大学生态与环境科学学院上海200241 华东师范大学上海市城市化生态过程与生态恢复重点实验室上海200241 崇明生态研究院上海202162 自然资源部大都市区国土空间生态修复工程技术创新中心上海200062

以上海崇明东滩盐沼湿地近海区域不同群落(生境)土壤种子库为研究对象,通过在温室内模拟潮汐作用,探究土壤盐度、淹水频率及其交互作用对土壤种子库萌发动态的影响。结果表明:崇明东滩盐沼湿地近海区域海三棱藨草(×Bolboschoenoplectus... 详细信息

以上海崇明东滩盐沼湿地近海区域不同群落(生境)土壤种子库为研究对象,通过在温室内模拟潮汐作用,探究土壤盐度、淹水频率及其交互作用对土壤种子库萌发动态的影响。结果表明:崇明东滩盐沼湿地近海区域海三棱藨草(×Bolboschoenoplectus mariqueter(Tang et ***)Tatanov)群落、互花米草(Spartina alterniflora Loisel.)群落、芦苇(Phragmites australis(Cav.)*** Steud.)群落和光滩生境土壤种子库共萌发出13种植物,隶属于7科12属,其中海三棱藨草、马唐(Digitaria sanguinalis(Linn.)Scop.)和升马唐(Digitaria ciliaris(Retz.)Koeler)的总频度较高,分别为0.108、0.064和0.059。禾本科(Poaceae)和莎草科(Cyperaceae)是崇明东滩盐沼湿地近海区域土壤种子库萌发植物群落的典型科。本地植物(海三棱藨草和芦苇)群落土壤种子库主要萌发海三棱藨草、马唐和升马唐;而入侵植物(互花米草)群落土壤种子库主要萌发马唐、升马唐和碱菀(Tripolium pannonicum(Jacquin)Dobroczajeva),其中碱菀仅在互花米草群落土壤种子库中萌发。海三棱藨草群落土壤种子库对不同盐度和淹水频率的适应性较强。除光滩生境外,其他3种群落土壤种子库在盐度0.0%、0.5%、1.0%和1.5%以及淹水频率1、3、7、10 d处理条件下均有海三棱藨草萌发。与对照(淡水湿润)处理条件相比较,不同盐度和淹水频率处理显著(P<0.05)降低了该区域土壤种子库萌发植物群落的植株密度和物种多样性。综上所述,在恢复崇明东滩盐沼湿地的本地植物群落时,利用土壤种子库是一个可行的途径,其中特别推荐海三棱藨草群落的土壤种子库。

关键词：土壤种子库盐沼湿地崇明东滩潮汐作用盐度淹水频率

融合灰度和梯度方向信息的随机游走的图像分割

在线全文

学校读者我要写书评

暂无评论

云南大学学报（自然科学版） 2010年第4期32卷 413-417,423页

作者：于佳丽郭敏陕西师范大学计算机科学学院陕西西安710062

针对传统图像分割方法在处理梯度变化较大的图像中存在的缺陷,以随机游走算法为基础,在原始的像素的灰度信息的基础上,融合了像素间的梯度差信息作为图网络的权重,以更好地描述像素与其相邻像素间的关系,通过用户指定的种子点信息,借助... 详细信息

针对传统图像分割方法在处理梯度变化较大的图像中存在的缺陷,以随机游走算法为基础,在原始的像素的灰度信息的基础上,融合了像素间的梯度差信息作为图网络的权重,以更好地描述像素与其相邻像素间的关系,通过用户指定的种子点信息,借助于电路模拟以及线性方程的系统,使得随机游走者从每个非种子点沿着最大概率的边逐渐走向正确的标记点(目标点或背景点)即为其最可能属于的区域,从而最终实现图像的分割.实验结果表明,方法适合于梯度变化较大的图像,不仅保留了原有算法抗噪声的优势,而且运算效率较高,是一种有效的图像分割方法.

关键词：随机游走梯度方向信息图像分割

Benzoylation of benzene and substituted benzenes catalyzed by superacid ZrO_2:H_2SO_4

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Chemistry 1993年第5期11卷 452-456页

作者： jia,Cheng-Guo HUANG,Mei-yu jiaNG,Ying-Yan Institute of Chemistry,Chinese Academy of Sciences,Beijing 100080 Institute of Chemistry Chinese Academy of Sciences Beijing 100080

Superacid ZrO_2:H_2SO_4 showed high activity in Friedel-Crafts benzoylation of benzene and substituted benzenes such an chlorobenzene,toluene and 1,3,*** in 90-100% yields were obtained with catalytic amount of superacid ZrO_2:H_2SO_*** calcination temperature greatly influenced the acid strength and activity of the superacid ZrO_2:H_2SO_*** superacid has both Lewis and Bronsted acid *** reversibility of Friedel-Crafts benzoylation and transacylation were observed over the *** used superacid could be readily regenerated and showed identical benzoylation activity to toluene.

关键词： Zr Benzoylation of benzene and substituted benzenes catalyzed by superacid ZrO2 SO

在线全文

学校读者我要写书评

暂无评论

面向无人机集群的双层分组拜占庭容错算法

通信学报 2022年第1期43卷 96-103页

作者：陈宇贾连兴国防科技大学信息通信学院湖北武汉430073

针对区块链技术应用于无人机集群通信时存在的通信复杂度高、稳健性差等问题,提出了一种双层分组拜占庭容错算法。根据无人机的编队结果对节点进行分组,并从每组选取一部分高信誉节点组成委员会,其他节点作为共用节点,形成双层分组共识... 详细信息

针对区块链技术应用于无人机集群通信时存在的通信复杂度高、稳健性差等问题,提出了一种双层分组拜占庭容错算法。根据无人机的编队结果对节点进行分组,并从每组选取一部分高信誉节点组成委员会,其他节点作为共用节点,形成双层分组共识结构。使用门限签名技术降低通信复杂度,仅通过委员会节点与其他分组节点通信,减少分组间通信次数,使平均通信时延大幅度减小。分层结构使主节点身份隐匿于委员会之中,降低了主节点被敌方自适应攻击的风险,提升了系统的稳健性。实验结果表明,所提算法相比于对比算法,共识过程的时延显著降低,同时能够有效保证系统的活性。

关键词：无人机集群拜占庭容错共识算法双层分组结构

维普期刊数据库博看期刊

同方期刊数据库

在线全文

学校读者我要写书评

暂无评论

基于3D打印的离散型产品可制造性优化问题

计算机集成制造系统 2016年第5期22卷 1229-1234页

作者：韩钰贾国柱北京航空航天大学经济管理学院北京100191

为了定量描述3D打印技术对生产管理的影响,构建了基于3D打印的离散型产品可制造性优化模型,设计了优化模型的算法并进行了算例研究,定量分析了传统制造方式与3D打印技术的生产成本与目标零件复杂度的关系。该模型和算法能够解决3D打印... 详细信息

为了定量描述3D打印技术对生产管理的影响,构建了基于3D打印的离散型产品可制造性优化模型,设计了优化模型的算法并进行了算例研究,定量分析了传统制造方式与3D打印技术的生产成本与目标零件复杂度的关系。该模型和算法能够解决3D打印与传统制造工艺相结合的产品可制造性优化问题,有助于基于制造成本目标获得优化的产品设计和工艺规划方案,为推动3D打印在工业生产中的广泛应用及其进一步产业化提供了一定的参考。

关键词： 3D打印可制造性制造成本离散型产品

Effect of pressure on the elastic properties and optoelectronic behavior of Zn_4B_6O_(13): First-principles investigation

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2018年第5期27卷 430-439页

作者： Pei-Da Wang Zhen-yuan jia yu-Han Zhong Hua-yue Mei Chun-Mei Li Nan-Pu Cheng Faculty of Materials and Energy Southwest University Chongqing 400715 China

The hydrostatic-pressure-dependent mechanical stability and optoelectronic behavior of Zn_4B_6O_（13）（ZBO） are calculated using the exchange-correlation functional Perdew–Burke–Ernzerhof generalized gradient approximation and the hybrid functional PBE0 based on density functional theory. The calculated and experimental unit cell volumes and Vickers hardness of ZBO at zero pressure agree well. ZBO is mechanically stable under the critical pressure of 52.98 GPa according to the generalized stability criteria. Furthermore, Young＇s modulus and Vickers hardness decrease with increasing hydrostatic pressure. The strength and type of ZBO bonds are investigated by population and electron density difference. The electronic structure at zero pressure reveals that ZBO is an indirect band gap semiconductor, and the calculated 5.62-e V bandgap coincides well with the 5.73-e V experimental value, highlighting the success of the hybrid functional PBE0 calculations of electronic properties. The band gap almost increases as a second-order polynomial of pressure, and the indirect nature does not change with the applied external pressure. The optical reflectivity and absorption coefficient show that ZBO is an excellent ultraviolet photodetector. Our calculation results suggest that the elastic and optical properties of ZBO are highly stable over a wide pressure range.

关键词： Zn4B6O13 crystal density functional theory elastic properties optical properties

Numerical investigation of radio-frequency negative hydrogen ion sources by a three-dimensional fluid model

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2021年第9期30卷 335-345页

作者： Ying-Jie Wang jia-Wei Huang Quan-Zhi Zhang yu-Ru Zhang Fei Gao You-Nian Wang Key Laboratory of Materials Modification by Laser Ionand Electron Beams(Ministry of Education)School of PhysicsDalian University of TechnologyDalian 116024China

A three-dimensional fluid model is developed to investigate the radio-frequency inductively coupled H2 plasma in a reactor with a rectangular expansion chamber and a cylindrical driver chamber,for neutral beam injection system in *** this model,the electron effective collision frequency and the ion mobility at high E-fields are employed,for accurate simulation of discharges at low pressures(0.3 Pa-2 Pa)and high powers(40 kW-100 kW).The results indicate that when the high E-field ion mobility is taken into account,the electron density is about four times higher than the value in the low E-field *** addition,the influences of the magnetic field,pressure and power on the electron density and electron temperature are *** is found that the electron density and electron temperature in the xz-plane along permanent magnet side become much more asymmetric when magnetic field ***,the plasma parameters in the yz-plane without permanent magnet side are symmetric no matter the magnetic field is applied or ***,the maximum of the electron density first increases and then decreases with magnetic field,while the electron temperature at the bottom of the expansion region first decreases and then almost keeps *** the pressure increases from 0.3 Pa to 2 Pa,the electron density becomes higher,with the maximum moving upwards to the driver region,and the symmetry of the electron temperature in the xz-plane becomes much *** power increases,the electron density rises,whereas the spatial distribution is *** can be summarized that the magnetic field and gas pressure have great influence on the symmetry of the plasma parameters,while the power only has little effect.

关键词： negative hydrogen ion source inductively coupled plasma three-dimensional fluid model magnetic field effect

Synthesis and Properties of Reversible Disulfide Bond-based Self-healing Polyurethane with Triple Shape Memory Properties

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Polymer Science 2019年第11期37卷 1119-1129页

作者： Han jia Kun Chang Shu-Ying Gu Department of Polymeric Materials School of Materials Science and Engineering Tongji University Shanghai 201804 China Key Laboratory of Advanced Civil Engineering Materials Ministry of Education Tongji University Shanghai 201804 China

A reversible disulfide bond-based self-healing polyurethane with triple shape memory properties was prepared by chain extending of random copolymer poly(lactide-co-caprolactone)(PCLA), hexamethylene diisocyanate (HDI), polytetrahydrofuran (PTMEG), and 4,4,-aminophenyl disulfide. The chemical structures were characterized using 1H nuclear magnetic resonance (^1H-NMR) spectroscopy, Fourier transform infrared spectroscopy (FTIR), and gel permeation chromatography (GPC). The thermal properties, selfhealing properties, triple-shape memory effect, and quantitative shape memory response were evaluated by differential scanning calorimetry (DSC), tensile tests, two-step programming process thermal mechanical experiments, and subsequent progressive thermal recovery. The self-healing mechanism and procedures were investigated using polarizing optical microscopy (POM) and an optical profiler. It was concluded that self-healing properties (up to 60%) and triple-shape memory properties around 35 and 50℃(with shape fixation ratios of 94.3% and 98.3%, shape recovery ratios of 76.6% and 85.1%, respectively) were integrated to the shape memory polyurethane. As-prepared polyurethane is expected to have potential applications in multi-shape coatings, films, and step-by-step deploying structures.

关键词： Self-healing Reversible disulfide bond Triple shape memory Polyurethane

Effects of dynamic flow rates on degradation deposition behavior of Mg scaffold

在线全文

学校读者我要写书评

暂无评论

Journal of Magnesium and Alloys 2023年第6期11卷 2054-2060页

作者： Gaozhi jia Meng Zhou Yicong Huang Chenxin Chen Liang Jin Qian Wu jian Weng Fei yu Ao Xiong Guangyin yuan Frank Feyerabend Hui Zeng Department of Bone&Joint Surgery Peking University Shenzhen HospitalShenzhen Peking University-The Hong Kong University of Science and Technology Medical CenterShenzhen Institute of Information TechnologyShenzhen 518036China National Engineering Research Center of Light Alloy Net Forming&State Key Laboratory of Metal Matrix Composite Shanghai Jiao Tong UniversityShanghai 200240China Beijing Key Laboratory of Civil Aircraft Structures and Composite Materials Beijing Aircraft Technology Research Institute of COMACBeijing 102211China College of Life Science Zhejiang Chinese Medical UniversityHangzhou 310053China Shenzhen Branch Guangdong Laboratory of Lingnan Modern AgricultureGenome Analysis Laboratory of the Ministry of Agriculture and Rural AffairsAgricultural Genomics Institute at ShenzhenChinese Academy of Agricultural SciencesShenzhen 518120China Department of Orthopaedics Peking University People’s HospitalBeijing 100044China Division of Metallic Biomaterials Institute of Materials ResearchHelmholtz-Zentrum HereonGeesthacht 21502Germany National&Local Joint Engineering Research Center of Orthopaedic Biomaterials Peking University Shenzhen HospitalShenzhen 518036China

Degradability of bone tissue engineering scaffold that matching the regeneration rate could allow a complete replacement of host ***,the porous structure of biodegradable Mg scaffolds certainly generated high specific surface area,and the three-dimensional interconnected pores provided fast pervasive invasion entrance for the corrosive medium,rising concern of the structural integrity during the *** clarify the structural evolution of the three-dimensional(3D)porous structure,semi-static immersion tests were carried out to evaluate the degradation performance in our previous ***,dynamic immersion tests mimicking the in vivo circulatory fluid through the interconnected porous structure have yet been ***,the effects of dynamic flow rates on the degradation deposition behavior of 3D porous Mg scaffolds were rarely *** this study,Mg scaffolds degraded at three flow rates exhibited different degradation rates and deposition process.A flow rate of 0.5 m L/min introduced maximum drop of porosity by accumulated deposition *** deposition products provided limited protection against the degradation process at a flow rate of 1.0 m L/*** three-dimensional interconnected porous structure of Mg scaffold degraded at 2.0 m L/min well retained after 14 days showing the best interconnectivity resistance to the degradation deposition *** dynamic immersion tests disclosed the reason for the different degradation rates on account of flow rates,which may bring insight into understanding of varied in vivo degradation rates related to implantation sites.

关键词： Porous Mg scaffold Degradability Porosity Dynamic immersion test Degradation rate