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A Facile Strategy for Intrinsic Low-Dk and Low-Df Polyimides Enabled by Spirobifluorene Groups

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Chinese Journal of Polymer Science 2023年第2期41卷 288-296页

作者： Wan-Yi Tan Ling-Feng Jian Wei-Peng Chen yong-Wen Zhang Xiao-Chuang Lu Wan-Jun Huang Ji-Sheng Zhang Jing-Wu Wu Jun-Li Feng Yi-Dong Liu Ting-Ting Cui yong-gang min Guangdong University of Technology(GDUT) Guangzhou510006China Huimai Materials Technology(Guangdong)Co. Ltd.Foshan528200China Shenzhen Customs Industrial Product Inspection Technology Center Shenzhen518026China

Modified polyimides(MPIs)show great potential towards 5G communication applications,due to its excellent thermal stability,mechanical property and chemical stability as compared to most of *** fluoride groups or porous structure is favorable to ultra-low dielectric constant(D_(k))and dielectric loss(D_(f)).However,the cost of the fluorinated MPIs is high and their synthetic processes are complicated,and porous MPIs suffer poor mechanical ***,increasing the fraction of free volume is a very effective way to lower D_(k)through introducing more ultra-low-D_(k)air ***,most of this kind of MPIs lag far behind the fluorinated MPIs and the porous MPIs in terms of ultra-low D_(f),hindering the application of MPIs in high-speed communication ***,it is highly desirable to develop intrinsic ultra-low-D_(k)/D_(f)MPIs at high frequency with less fluoric groups and nonporous ***,we introduce a facile and effective strategy to lower D_(k)and D_(f)through introducing rigid and large sterically hindered aromatic groups into *** the one hand,their large steric hindrance effect leads to low D_(k)by increasing intrinsic free *** the other hand,the resulting highly stiff polymer chain and strong intermolecular interaction are favorable to reduce D_(f)by inhibiting dipole *** on this strategy,the spirobifluorene groups are *** as-prepared MPIs show excellent dielectric performance with low D_(k)of 2.74–2.76 and low D_(f)of 0.00599 at 10 GHz,to some extent,exceeding the multiple fluorinated MPI with D_(k)/D_(f)of 2.67/0.00663 at 10 GHz.

关键词： Polyimide High speed communication Low dielectric constant Low dielectric loss

带有色厚尾量测噪声的鲁棒高斯近似滤波器和平滑器

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自动化学报 2017年第1期43卷 114-131页

作者：黄玉龙张勇刚武哲民李宁王刚哈尔滨工程大学自动化学院哈尔滨150001 哈尔滨工业大学电气工程及自动化学院哈尔滨150080 中国舰船研究设计中心武汉430064

为了解决带有色厚尾量测噪声的非线性状态估计问题,本文提出了新的鲁棒高斯近似(Gaussian approximate,GA)滤波器和平滑器.首先,基于状态扩展方法将量测差分后带一步延迟状态和白色厚尾量测噪声的非线性状态估计问题,转化成带厚尾量测... 详细信息

为了解决带有色厚尾量测噪声的非线性状态估计问题,本文提出了新的鲁棒高斯近似(Gaussian approximate,GA)滤波器和平滑器.首先,基于状态扩展方法将量测差分后带一步延迟状态和白色厚尾量测噪声的非线性状态估计问题,转化成带厚尾量测噪声的标准非线性状态估计问题.其次,针对量测差分后模型中的噪声尺度矩阵和自由度(Degrees of freedom,DOF)参数未知问题,设计了新的高斯近似滤波器和平滑器,通过建立未知参数和待估计状态的共轭先验分布,并利用变分贝叶斯方法同时估计未知的状态、尺度矩阵、自由度参数.最后,利用目标跟踪仿真验证了本文提出的带有色厚尾量测噪声的鲁棒高斯近似滤波器和平滑器的有效性以及与现有方法相比的优越性.

关键词：非线性状态估计有色厚尾量测噪声变分贝叶斯 Student s t分布状态扩展方法

大黄-桃仁药对不同配比对大黄中10种成分提取量的影响

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中药材 2016年第7期39卷 1578-1581页

作者：颜永刚尹立敏王红艳王洁刘姣姣邓翀陕西中医药大学陕西咸阳712046

目的:考察大黄-桃仁药对不同配比对大黄中10种成分提取量的影响。方法:以均匀法设置不同配比的大黄-桃仁药对(1∶5、2∶5、2∶3、1∶1、3∶2、5∶2、5∶1),同时设置大黄对照组(大黄-桃仁1∶0),采用HPLC法测定不同配比药对中没食子酸、(... 详细信息

目的:考察大黄-桃仁药对不同配比对大黄中10种成分提取量的影响。方法:以均匀法设置不同配比的大黄-桃仁药对(1∶5、2∶5、2∶3、1∶1、3∶2、5∶2、5∶1),同时设置大黄对照组(大黄-桃仁1∶0),采用HPLC法测定不同配比药对中没食子酸、(+)-儿茶素、番泻苷B、蒽醌类(芦荟大黄素、大黄酸、大黄素、大黄酚、大黄素甲醚、大黄酚-1-O-葡萄糖苷、大黄素-8-O-葡萄糖苷)10种成分的含量,分析10种成分提取量的变化。结果:与大黄对照组比较,大黄-桃仁不同配比样品(5∶1、5∶2、3∶2)中随着桃仁比例的升高,大黄中的10种成分提取量逐渐减少;1∶1样品中大黄的10种成分提取量达到最低值。大黄-桃仁不同配比样品(2∶3、2∶5、1∶5)中随着桃仁比例的升高,大黄中的没食子酸、(+)-儿茶素、大黄酚的提取量明显升高。结论:配伍不同比例的桃仁后,大黄中10种成分提取量发生明显变化,特别是大黄-桃仁药对(2∶3、2∶5、1∶5)中,没食子酸、(+)-儿茶素、番泻苷B、芦荟大黄素、大黄素、大黄酚、大黄素甲醚、大黄素-8-O-葡萄糖苷8种成分的提取量明显高于大黄对照组。

关键词：大黄-桃仁药对 HPLC 没食子酸 (+)-儿茶素番泻苷B 蒽醌类

Modeling dual-scale epidemic dynamics on complex networks with reaction diffusion processes

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Journal of Zhejiang University-Science C(Computers and Electronics) 2014年第4期15卷 265-274页

作者： Xiao-gang JIN yong min AI Institute in College of Computer Science and Technology Zhejiang University College of Computer Science and Technology Zhejiang University of Technology

The frequent outbreak of severe foodborne diseases(e.g., haemolytic uraemic syndrome and Listeriosis) in 2011 warns of a potential threat that world trade could spread fatal pathogens(e.g., enterohemorrhagic Escherichia coli). The epidemic potential from trade involves both intra-proliferation and inter-diffusion. Here, we present a worldwide vegetable trade network and a stochastic computational model to simulate global trade-mediated epidemics by considering the weighted nodes and edges of the network and the dual-scale dynamics of epidemics. We address two basic issues of network structural impact in global epidemic patterns:(1) in contrast to the prediction of heterogeneous network models, the broad variability of node degree and edge weights of the vegetable trade network do not determine the threshold of global epidemics;(2) a ‘penetration effect', by which community structures do not restrict propagation at the global scale, quickly facilitates bridging the edges between communities, and leads to synchronized diffusion throughout the entire network. We have also defined an appropriate metric that combines dual-scale behavior and enables quantification of the critical role of bridging edges in disease diffusion from widespread trading. The unusual structure mechanisms of the trade network model may be useful in producing strategies for adaptive immunity and reducing international trade frictions.

关键词： Worldwide trade networks Foodbome diseases Scale-free networks Mean-field analysis

Influence of semisolid forging ratio on the microstructure and mechanical properties of Ti14 alloy

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International Journal of minerals,Metallurgy and Materials 2013年第3期20卷 266-272页

作者： yong-nan Chen gang Liu Xue-min Zhang yong-qing Zhao State Key Laboratory for Mechanical Behavior of Material Xi'an Jiaotong University School of Materials Science and Engineering Chang'an University Northwest Institute for Nonferrous Metal Research

The present work is focused on the microstructure and mechanical properties of Ti14 alloy with different semisolid deformation ratios during forging tests. The results revealed that the forging ratio had a significant effect on the precipitation of the alloy. Fewer plate-shaped Ti2Cu tended to precipitate on grain boundaries with higher forging ratios, and finally the plate-shaped Ti2Cu formed precipitate-free zones along grain boundaries with a forging ratio of 75%. The precipitation on grain boundaries was found to be controlled by a peritectic reaction. Large forging ratios accelerated the extrusion of liquid and resulted in less liquid along the prior grain boundaries, which reduced the peritectic precipitation in this region and formed precipitate-free zones during re-solidification. In addition, increasing the forging ratio could accelerate dynamic recrystallization, which is favorable for improving the semisolid formability. The tensile ductility increased with increasing forging ratio, and a mixed fracture mode, involving both cleavage and dimple fracture, was observed after forging with a forging ratio of 75%, which along grain boundaries during semisolid processing. is attributed to the presence of precipitate-free zones formed

关键词： titanium alloys semisolid forging microstructure precipitates mechanical properties

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锗锡浓度对硅锗锡合金性能影响的研究

原子与分子物理学报 2025年第5期42卷 163-174页

作者：顾永顺温淑敏内蒙古工业大学理学院呼和浩特010051

由于SiGeSn合金材料其具有高的载流子迁移率和较长的载流子寿命,并且其结构具有较高的热力学稳定性,所以在光电子领域中是一种具有非常大应用潜力的半导体材料.本文采用密度泛函理论中的广义梯度近似GGA+U的方法,构建并计算了本征半导体... 详细信息

由于SiGeSn合金材料其具有高的载流子迁移率和较长的载流子寿命,并且其结构具有较高的热力学稳定性,所以在光电子领域中是一种具有非常大应用潜力的半导体材料.本文采用密度泛函理论中的广义梯度近似GGA+U的方法,构建并计算了本征半导体Si_(96)与五组掺杂模型Si_(92)Ge_(2)Sn_(2)、Si_(88)Ge_(4)Sn_(4)、Si_(84)Ge_(6)Sn_(6)、Si_(80)Ge_(8)Sn_(8)、Si_(76)Ge_(10)Sn_(10)的电子结构及光学性质.通过对计算结果的分析可知,Ge,Sn的加入使得Si材料的带隙宽度减小,并且发生了由间接带隙向直接带隙的转变;Ge,Sn浓度最高的SiGeSn合金的形成能相对较高,稳定性相较于Ge,Sn含量低的材料较差;随着Ge,Sn掺杂浓度的提高,电子态密度图显示出越来越明显的杂化现象,并且态密度的峰值主要有Si原子的s轨道提供;Ge,Sn浓度的提高还使得SiGeSn合金的吸收系数在可见光及近红外区域内增加、反射率在可见光及以上波段范围内提高、折射率变低、消光系数曲线向红外区域移动等光学性质变化,表明可以通过调节Ge,Sn浓度来获得合适的光学特性,这为SiGeSn半导体在红外区域光电材料和器件的应用上提供了研究方向.

关键词： SiGeSn 电子特性光学性质

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基于摆锤法的成熟期油菜角果炸荚因素试验分析

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农机化研究 2025年第4期47卷 180-185页

作者：李港张敏魏德欣江东农业农村部南京农业机械化研究所南京210014

为了降低油菜联合收割机拨禾轮拨禾过程对角果打击造成的炸荚损失,采用摆锤法模拟拨禾轮拨禾对油菜角果冲击过程,对影响拨禾过程中的炸荚因素进行测试分析,并对角果损伤变化形式及过程进行分析。试验结果表明:摆锤冲击速度3.5 m/s、夹... 详细信息

为了降低油菜联合收割机拨禾轮拨禾过程对角果打击造成的炸荚损失,采用摆锤法模拟拨禾轮拨禾对油菜角果冲击过程,对影响拨禾过程中的炸荚因素进行测试分析,并对角果损伤变化形式及过程进行分析。试验结果表明:摆锤冲击速度3.5 m/s、夹持果柄位置距连接点2 mm是区分角果抗打击炸荚的最优参数;油菜角果炸荚不仅与冲击速度、果柄夹持位置有关,而且与油菜品种、冲击件材料类型、角果受力面、含水率、角果在植株上的分布位置等都有关系;冲击速度不超过1.5 m/s时,角果损伤以角果果柄发生塑性变形为主;冲击速度为2.5~4.5 m/s时,角果损伤以果皮破裂分离、果柄弹性变形为主。研究结果可为油菜拨禾轮设计和工作参数选择提供参考。

关键词：油菜角果炸荚率冲击拨禾轮摆锤法

维普期刊数据库博看期刊

Reconstruction of plasmoid and traveling compression region in the near-Earth magnetotail

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Science China(Technological Sciences) 2015年第2期58卷 330-337页

作者： LU Shang Wen ZONG Qiu gang VOGIATZIS Ioannis WANG yong Fu TIAN An min Institute of Space Physics and Applied Technology Peking University Department of Electrical and Computer Engineering Democritus University of Thrace Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment School of Space Science and PhysicsShandong University at Weihai

Cluster spacecraft observed an earthward flowing plasmoid along with a travelling compression region （TCR） structure in southern plasma sheet boundary layer （PSBL） at 21：09 UT of September 19, 2001. We have reconstructed the two-dimensional topology of the magnetic field structure observed by C1 using Grad-Shafranov reconstruction method. Results show that CI passed through part of a plasmoid, which compressed the lobe magnetic field and formed a TCR. The size of the whole plas- moid structure in X direction is estimated to be about 3 Re. Furthermore, using multi-spacecraft observations, we have found some detailed information about this structure. First, C1 observed bi-streaming electron components, which supports our sug- gestion that the spacecraft passed through closed field lines. Second, a small magnetic field perturbation within this plasmoid accompanied by slight decrease in electron flux suggests that a flux rope core might exist at the center of the plasmoid.

关键词： plasma sheet boundary layer plasmoid traveling compression region Grad-Shafranov method

Catastrophic Debris Flows on July 10^(th) 2013 along the min River in Areas Seriously-hit by the Wenchuan Earthquake

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Journal of Mountain Science 2015年第1期12卷 186-206页

作者： GE yong-gang CUI Peng ZHANG Jian-qiang ZENG Chao SU Feng-huan Key Laboratory of Mountain Hazards and Earth Surface Processes/Chengdu Institute of Mountain Hazards and Environment Chinese Academy of Sciences CAS Center for Excellence in Tibetan Plateau Earth Sciences Sichuan Engineering Research Center for Emergency Mapping & Disaster Reduction

Over 240 debris flows occurred in hill-slopes, gullies （ indicated those with single-channel） and watersheds （indicated those with tributaries and channels） on July 10th 2013 in the Wenchuan county, and caused 29 casualties and about 633×10^6 USD losses. This work aimed to analyze characteristics, hazards and causes of these events and explore mitigating measures based on field investigation and remote sensing images interpretation. The debris flows contained clay content of 0.1%~3.56%, having densities of 1.72-2.14 t/m^3, velocities of 5.0-m.7 m/s, discharges of 335-2353 m^3/s and sediment yields of 0.10-1.26×10^6 m^3, and also numerously occurred in large watersheds with the area over lo km^2. Large debris flows formed 3 hazard-chains in slopes, gullies, watersheds and rivers, which all evolved in dammed lakes and outburst flood, and 26 dammed lakes and lO newly ones were generated along the rivers of min and Yuzi. The remarkable spatial difference of loose solid materials accumulation and intense rainfall, with the cumulative of about or more than 150 mm and the hourly of over 16mm, caused debris flows in the sections from Yingxiu to Miansi and Gengda. The damages on buildings, reconstructions, highways,factories and hydro power station originated from the impacting, scouring, burying of debris flows, the submerging of dammed lake and the scouring of outburst flood, and the huge losses came from the ruinous destructions of control engineering works of debris flows as well as the irrational location and low- resistant capabilities of reconstructions. For hazards mitigating of debris flows in long term, the feasible measures for short term, including risk-reassessing of foregone and potential hazard sites, regional alarming system establishing and integrated control in disastrous sites, and middle-long term, including improving reconstruction standard, rationally disposing river channel bed rise and selecting appropriate reconstruction time and plans, were strongly

关键词： Debris flows Wenchuan Earthquake Characteristics Damages Causes Preventions