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Effect of Low-temperature Imidization on Properties and Aggregation Structures of Polyimide Films with Different Rigidity

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Chinese Journal of Polymer Science 2024年第8期42卷 1134-1146页

作者： Yan Jia Lei Zhai song mo Yi Liu Li-Xin Liu Xin-Yu Du Min-Hui He Lin Fan Key Laboratory of Science and Technology on High-tech Polymer Materials Institute of ChemistryChinese Academy of SciencesBeijing 100190China School of Chemical Sciences University of Chinese Academy of SciencesBeijing 100049China

The traditional high-temperature preparation process of polyimide can cause many problems and limits the wider application in extreme *** important challenge to be solved urgently is the reduction of imidization *** this work,twelve kinds of polyimide films with different chain rigidity were prepared at low temperature of 200℃,in the absence or presence of imidazole used as the *** molecular rigidity and free volume were theoretically calculated,and relationship between structure and properties were systematically *** results show that imidization reaction under low temperatures is significantly affected by the rigidity of molecula r *** rigid structure of polyimide is not conducive to the low-temperature imidization,but this adverse effect can be eliminated by adding catalyst,resulting the notably increased imidization *** optical and thermal properties can be improved to a certain extent for the chemically catalyzed system,resulting in relatively higher heat resistance and thermal *** the mechanical performance could be determined by com plicating factors,greatly different from polyimide films prepa red by high temperature *** investigate aggregation structures of film s,the effect of chain rigidity and catalyst on the stacking or orientation of molecular chains was further *** wo rk can contribute to the understanding of chemically catalyzed imidization that is rarely reported in the existing research,and will provide guidance for the low-temperature preparation of high-performance polyimides.

关键词： Polyimide Imidization Catalyst Structure and properties Aggregation structures

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Effects of low molecular weight polysaccharide from Sargassum thunbergii against palmitic acid-induced intracellular lipid accumulation in 3T3-L1 adipocyte and HepG2 cells

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Food Science and Human Wellness 2024年第4期13卷 2244-2252页

作者： Hyo-Geun Lee D.P.Nagahawatta M.J.M.S.Kurera Kyung-mo song Yun-Sang Choi You-Jin Jeon Min-Cheol Kang Department of Marine Life Sciences Jeju National UniversityJeju 63243Republic of Korea Department of Biotechnology Faculty of Agriculture and Plantation ManagementWayamba University of Sri LankaMakanduraGonawila(NWP)60170Sri Lanka Research Group of Food Processing Korea Food Research Institute245Wanju 55365Republic of Korea

Low molecular weight polysaccharides can be isolated from Sargassum thunbergii(LMPST)and in vitro experiments were conducted to evaluate the inhibitory effects on *** natures of LMPST were attained from *** and appraised their LMPST on palmitic acid(PA)induced lipid accretion in Hep G2,and 3T3-L1 *** treatment lessened lipid deposition and intracellular free fatty acid and triglyceride intensities in PA-treated above mentioned *** mechanistic study publicized that LMPST2 significantly suppressed adipogenesis and stimulated the PA-treated 3T3-L1 cells occupied in the lipolysis ***,in PA-treated Hep G2 cells,the free fatty acid oxidation was significantly increased by *** these constructive properties of LMPST2 from ***,is a potential candidate for diminishing the intracellular lipids,and for a therapeutic agent in those conditions.

关键词： Sargassum thunbergii Low molecular weight polysaccharide Lipid accumulation Obesity Liver steatosis

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Anti-obesity effects of fucoidan from Sargassum thunbergii in adipocytes and high fat diet induced obese mice through inhibiting adipogenic specific transcription factor

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Food Science and Human Wellness 2024年第3期13卷 1608-1616页

作者： Hyo-Geun Lee H.H.A.C.K.Jayawardhana Fengqi Yang D.P.Nagahawaththa N.M.Liyanage Kyung-mo song Yun-Sang Choi Seung-Hong Lee You-Jin Jeon Min-Cheol Kang Department of Marine Life Sciences Jeju National UniversityJeju 63243Republic of Korea Marine Science Institute Jeju National UniversityJeju 63333Republic of Korea Research Group of Food Processing Korea Food Research InstituteWanju 55365Republic of Korea Department of Pharmoceutical Engineering Soonchunhyang UniversityAsan 31538Republic of Korea

The prevalence of obesity has increased and is a health concern *** to the concerns regarding synthetic anti-obesity treatments,nowadays natural products become a *** studies proved that there is a potential to use marine algae as anti-obesity ***,in this study,the lipid inhibitory effect of crude polysaccharide of amyloglucosidase-assisted hydrolysate from Sargassum thunbergii(STAC)and its fucoidan fractions(STAFs)on 3T3-L1 cells and high-fat diet(HFD)-induced obese mice were *** to the results,the STAF3,showed the highest xylose content and exhibited significant inhibitory effects on lipid accumulation by downregulating adipogenic and lipogenic proteins in 3T3-L1 ***,oral supplementation with STAC significantly declined gain in body weight and fat weight,and serum lipid contents in an HFD-induced obesity mouse *** and chemical characterizations demonstrated that puritied STAF3 has consistent surface morphology and small particle size,with similar structural characteristics as commercial ***,these results indicate that STAC and purified STAF3 from Sargassum thunbergia is a potent source to develop as ananti-obesity agents or functional food products to counter obesity.

关键词： Sargassum thunbergii Fucoidan Anti-obesity Anti-steatosis

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预见性护理干预在前列腺癌手术患者中的应用效果分析

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中外医药研究 2024年第7期3卷 93-95页

作者：宋墨徐州市肿瘤医院泌尿外科江苏徐州221000

目的:探讨预见性护理干预在前列腺癌手术患者中的应用效果。方法:选取2020年3月—2023年4月拟于徐州市肿瘤医院行前列腺癌手术的患者60例为研究对象,以随机抽签法分为两组,各30例。对照组予以常规护理干预,观察组予以预见性护理干预。... 详细信息

目的:探讨预见性护理干预在前列腺癌手术患者中的应用效果。方法:选取2020年3月—2023年4月拟于徐州市肿瘤医院行前列腺癌手术的患者60例为研究对象,以随机抽签法分为两组,各30例。对照组予以常规护理干预,观察组予以预见性护理干预。比较两组术后康复指标,患者心理弹性、控尿能力及术后并发症发生率。结果:观察组首次下床活动时间、首次肛门排气时间、首次排便时间、引流管拔除时间均短于对照组,差异有统计学意义(P<0.05);术后,两组乐观性、力量性、坚韧性评分均升高,观察组高于对照组,差异有统计学意义(P<0.05);术后,两组漏尿点压力、最大尿道闭合压均上升,观察组高于对照组,差异有统计学意义(P<0.05);观察组术后并发症发生率低于对照组,差异有统计学意义(P=0.030)。结论:预见性护理干预可有效降低前列腺癌患者术后并发症发生率,改善患者术后康复指标,提高心理弹性及控尿能力。

关键词：前列腺癌预见性护理术后并发症心理弹性控尿能力

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3D打印聚酰亚胺材料研究与进展

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中国科学：化学 2024年第6期54卷 856-870页

作者：杜新玉刘仪莫松何民辉翟磊范琳极端环境高分子材料重点实验室中国科学院化学研究所北京100190 中国科学院大学化学科学学院北京101408

3D打印可根据三维数字化模型在不使用模具的前提下将制件逐层成型,具有传统成型工艺难以企及的效率与经济优势,已在轨道交通和航空航天等领域得到应用.但可打印聚合物材料种类与性能不足,制约了3D打印从原型制备技术向工程制造技术的发... 详细信息

3D打印可根据三维数字化模型在不使用模具的前提下将制件逐层成型,具有传统成型工艺难以企及的效率与经济优势,已在轨道交通和航空航天等领域得到应用.但可打印聚合物材料种类与性能不足,制约了3D打印从原型制备技术向工程制造技术的发展.聚酰亚胺本征兼具高耐热性与优异力学性能,将3D打印技术与聚酰亚胺材料相结合有助于缩小3D打印与传统成型技术的差距,释放3D打印工业应用潜力.本文总结了近年来国内外3D打印聚酰亚胺的发展现状,重点从聚酰亚胺物理与化学特性调控、材料制备与改性、3D打印工艺与后处理工艺优化、打印件性能与功能以及尺寸稳定性等方面对熔融沉积、立体光刻、数字光处理、直接墨水书写、紫外辅助直接墨水书写以及选择性激光烧结成型聚酰亚胺的研究工作进行了介绍,并对3D打印聚酰亚胺未来发展面临的挑战进行了讨论分析.

关键词： 3D打印聚酰亚胺力学性能耐热性尺寸稳定性

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基于熵值法的铝合金缸体低压铸造工艺多目标优化

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铸造 2024年第6期73卷 753-761页

作者：邓伟宋仲模雷基林罗坤徐远志张勇昆明理工大学云南省内燃机重点实验室云南昆明650500 昆明云内动力股份有限公司云南昆明650224 成都正恒动力股份有限公司四川成都610500

基于有限元软件ProCAST构建某型铝合金缸体的有限元模型,设计L16(44)正交试验方案,探究了浇注温度、模具预热温度、充型时间、保压压力四个工艺参数对凝固时间和缩松体积的影响。采用熵值法分别计算两个评价指标的权重,将凝固时间与缩... 详细信息

基于有限元软件ProCAST构建某型铝合金缸体的有限元模型,设计L16(44)正交试验方案,探究了浇注温度、模具预热温度、充型时间、保压压力四个工艺参数对凝固时间和缩松体积的影响。采用熵值法分别计算两个评价指标的权重,将凝固时间与缩松体积转化为综合评分值进行单目标优化。通过极差分析与方差分析,得到了各参数对综合评分的影响程度为:浇注温度(A)>模具预热温度(B)>保压压力(D)>充型时间(C),确定了最优的工艺参数为A1B2C1D3。对比原工艺参数方案和优选工艺参数方案发现:凝固时间缩短了20.35%,缩松体积下降了2.96%。经生产试验,缸体铸件外观质量良好,无明显铸造缺陷,验证了最佳工艺参数的合理性。

关键词：铝合金缸体低压铸造正交试验熵值法多目标优化

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Thermally Conductive Polyimide/Boron Nitride Composite Films with Improved Interfacial Compatibility Based on modified Fillers by Polyimide Brushes

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Chinese Journal of Polymer Science 2023年第12期41卷 1921-1936,I0009页

作者： Meng-Yan Gao Lei Zhai song mo Yan Jia Yi Liu Min-Hui He Lin Fan Key Laboratory of Science and Technology on High-tech Polymer Materials Institute of ChemistryChinese Academy of SciencesBeijing 100190China School of Chemical Sciences University of Chinese Academy of SciencesBeijing 100049China

Polyimide-based composite films with high thermal conductivity,good mechanical property and electrical insulating performance are urgently needed in the electronics and microelectronics *** one of the key technical challenges to be solved,interfacial compatibility between filler and matrix plays an important role for composite ***,boron nitride was modified by grafting polyimide brushes via a twostep method,and a series of thermally conductive polyimide/boron nitride composite films were *** characterization and performance results proved that the interfacial interaction and compatibility was greatly enhanced,resulting in a significant reduction in defects and interfacial thermal *** interphase width of transition zone between two phases was also efficiently enlarged due to polyimide brushes grafted on filler *** a result,composite films based on polyimide-grafted boron nitride exhibited significantly improved properties compared with those based on pristine *** strength can reach up to 80 MPa even if the filler content is as high as 50 wt%.The out-of-plane and in-plane thermal conductivity of composite film increased to 0.841 and 0.850 W·m^(-1)·K^(-1),*** addition,thermal and dielectric properties of composite films were also enhanced to some *** above results indicate that surface modification by chemically grafting polymer brushes is an effective method to improve two-phase interfacial compatibility so as to prepare composite film with enhanced properties.

关键词： Polyimide Composite film Boron nitride Thermal conductivity Interfacial compatibility

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Effect of Aggregation Structure on Thermal Expansion Behavior of Polyimide Films with Different Thickness

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Chinese Journal of Polymer Science 2022年第12期40卷 1651-1661,I0010页

作者： Chang-Ou Wang Lei Zhai song mo Yi Liu Meng-Yan Gao Yan Jia Min-Hui He Lin Fan Key Laboratory of Science and Technology on High-tech Polymer Materials Institute of ChemistryChinese Academy of SciencesBeijing 100190China School of Chemical Sciences University of Chinese Academy of SciencesBeijing 100049China

Polyimide films derived from representative PMDA/ODA were prepared with thickness ranging from 5 μm to 25 μm,and the effect of aggregation structure on thermal expansion behavior along different directions was *** in-plane and out-of-plane linear thermal expansion(CTEand CTE) were respectively characterized by thermal mechanical analysis and FT-near-IR interference *** and anisotropic behavior of thermal expan sion were also *** increasing film thickness,CTEgradually increased from 32.2 ppm/℃ to46.1 ppm/℃ while CTEdecreased from 149.7 ppm/℃ to 128.2 ppm/℃.Volumetric thermal expansion of polyimide films was less sensitive to the va ried thickness,but anisotropy of thermal expansion was *** film of 5 μm thickness showed large birefringence,indicating more considerable in-plane chain orientation ***,molecular chains were more densely packed along in-plane direction when film thickness increased,while became loosely stacked in the out-of-plane *** contrast to the enhanced lateral chain packing for thicker film s,higher vertical chain packing order was found in thinner *** variation of aggregation structure during thermal expansion procedure was analyzed by temperature-dependent *** is proved that thermal expansion behavior of thinner films could be largely attributed to molecular chain packing,whereas that may be influenced by many factors for thicker films in addition to the effect of chain *** results revealed that thermal expansion of films with thickness variation is closely related to molecular chain orientation and packing,which is associated with both chemistry and morphological structure of polyimide.

关键词： Polyimide film Thermal expansion behavior Aggregation structure molecular chain packing Thickness variation

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Discourse analysis of knowledge-based live streaming:a case study of East Buy streamer Dong Yuhui

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Language and Semiotic Studies 2024年第2期10卷 222-244页

作者： Yehui song Junhua mo Korean Department Soochow UniversitySuzhou215006China English Department Soochow UniversitySuzhouChina

Live streaming e-commerce is not only an important part of China’s digital economy but also the preferred way of purchase for many Chinese,especially the *** 2022,a new model initiated by East Buy has emerged,quickly becoming known as knowledge-based live *** most famous streamer from this novel type of live streaming is Dong Yuhui,a former English teacher of the New Oriental *** a top Internet influencer with millions of followers,Dong Yuhui has become a conspicuous social sign of the rising China that is undergoing fast technological,economic,and cultural *** study thus takes Dong Yuhui as an example to examine the typical discourses of the knowledge-based live *** a triangulation of case study,discourse analysis,and sentiment analysis,it finds that Dong Yuhui mainly employs the strategies of disseminating encyclopedic knowledge,telling intriguing stories,and using poetic language in his live streaming *** unique discourse has the main function of fulfilling customers’intellectual,emotional,and psychological *** such,it is warmly received by customers,whose comments are centered on the talents of the streamer rather than the attributes of the commodity.

关键词： knowledge-based live streaming Dong Yuhui typical discourses major strategies main functions customer comments

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Unknown system dynamics estimator-based impedance control for lower limb exoskeleton with enhanced performance

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Control Theory and Technology 2024年第1期22卷 56-68页

作者： Wenhao Zhang Peng song Mingying Wu Qiang Li Xinmin mo Pingxin Ji Northwest Institute of Mechanical and Electrical Engineering Xianyang712099ShaanxiChina Xi’an Exo-Smart Dynamics Technology Ltd. Xi’an712046ShaanxiChina Department of Mechanical and Engineering Beijing Institute of TechnologyBeijing100081China

In this article, an unknown system dynamics estimator-based impedance control method is proposed for the lower limb exoskeleton to stimulate the tracking flexibility with the terminal target position when suffering parametric inaccuracies and unexpected disturbances. To reinforce the robust performance, via constructing the filtering operation-based dynamic relation, i.e., invariant manifold, the unknown system dynamics estimators are employed to maintain the accurate perturbation identification in both the hip and knee subsystem. Besides, a funnel control technique is designed to govern the convergence process within a minor overshoot and a higher steady-state precision. Meanwhile, an interactive complaint result can be obtained with the aid of the impedance control, where the prescribed terminal trajectory can be adjusted into the interaction variable-based target position by the force–position mapping, revealing the dynamic influence between the impedance coefficient (stiffness and damping) and the adjusted position magnitude. A sufficient stability analysis verifies the ultimately uniformly bounded results of all the error signals, and even the angle errors can be regulated within the predefined funnel boundary in the whole convergence. Finally, some simulations are provided to demonstrate the validity and superiority including the enhanced interaction flexibility and robustness.

关键词： Trajectory tracking Invariant manifold Funnel control Impedance control Lower limb exoskeleton

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