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聚乳酸与多糖都是生物可降解、生物相容性材料,将聚乳酸的力学性能优越性和多糖的生物学优越性能综合利用起来,设计生物仿生材料是一种制备生物医用材料的新手段。文中综合讨论了聚乳酸与多糖接枝改性的最新研究进展,同时对于这类生物仿生材料目前存在的问题以及前景进行了评估。 相似文献
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聚乳酸(PLA)作为一种新型的生物可降解材料,来源广泛、加工性能良好,但其硬而脆的属性限制了其在一些领域的应用。近年来,人们采用多种方法对PLA进行增强增韧改性以获得最优性能。文中针对PLA的特性、功能化和高性能化的发展趋势,并结合笔者课题组有关PLA的工作,首先揭示了PLA增强增韧的机理,然后从化学改性和物理改性两方面介绍了PLA的改性方法,随后讨论了聚乳酸与生物降解型和非生物降解型聚合物组成的复合材料,最后总结了聚乳酸在绿色电子器件、生物医用材料、形状记忆功能材料等领域中的应用,并对其未来的发展形势做出了展望,为开发新型聚乳酸增强增韧策略提供新的方法和思路。 相似文献
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食物接触材料的安全性能是大家普遍关心的问题。聚乳酸是近些年来发展起来的一种新型生物可降解材料,目前被广泛应用于食品包装材料中。本文介绍了聚乳酸的性质和在包装材料中的应用,并对其未来发展趋势进行了分析。通过模拟该材料在日常生活中实际接触环境进行迁移试验。结果表明:聚乳酸会在食品包装材料的不同使用环境下,产生不同程度的迁移。 相似文献
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聚乳酸是生物可降解、生物相容性材料,但由于存在亲水性差、缺乏细胞识别位点等缺陷,限制了其在生物医学工程中的应用.模拟细胞与基质相互作用的特点以及细胞外基质的特性,通过表面修饰、本体改性和复合加工的方法在聚乳酸中引入蛋白胶原、活性肽、多糖以及羟基磷灰石等生物活性分子,实现聚乳酸的仿生修饰,能够有效提高聚乳酸材料的生物学功能.综述了利用这些生物活性分子对聚乳酸进行仿生修饰的研究进展. 相似文献
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聚乳酸(PLA)是一种新型的生物基可再生生物降解材料,因具有高机械强度、易加工性、高熔点、可生物降解性和生物相容性等优点而得到广泛的关注。然而,其固有的脆性,即低断裂伸长率和断裂强度严重限制了它在实际中的应用,但也因此吸引了更广泛的深入研究。本文综述了以生物可降解高分子增韧聚乳酸的研究进展,重点阐述了生物基聚酯,生物基弹性体,植物基生物高分子,天然橡胶和植物油以及生物大分子增韧聚乳酸的最新研究发展概况,同时提出了在经过改善韧性之后,聚乳酸存在的冲击韧性弱以及低结晶速率和低热转变温度等问题,并分析了未来的发展方向和需要关注的主题。 相似文献
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聚(D,L-乳酸)基仿生聚合物材料的合成与表征 总被引:1,自引:0,他引:1
探索一种新型聚乳酸基仿生聚合物材料的制备新方法.具体实验步骤是:利用聚乳酸上叔碳原子的自由基反应活性,在过氧化二苯甲酰的催化作用下,将马来酸酐引入聚乳酸侧链上,以此提供高反应活性的酸酐键;然后利用酸酐基团与-NH2发生N-酰化反应这一特点,将脂肪族二胺引入聚乳酸侧链上,从而克服聚乳酸降解产物的体液环境呈酸性的缺陷;再用碳二亚胺作缩合剂,在二胺改性聚乳酸材料中共价引入一种细胞粘附肽段Arg-Gly-Asp-Ser(RGDS),赋予材料生物活性和生物特异性,这样就制备了一种新型聚乳酸基仿生材料.采用MALLS、FTIR和XPS对仿生材料进行结构表征;采用罗丹明比色法、茚三酮显色法和氨基酸分析仪检测法对仿生材料中的马来酸酐、二胺和粘附肽RGDS进行定量测定.结果表明,按文中所述之制备技术,在不改变聚乳酸材料主链结构的前提下,该仿生材料中粘附肽RGDS的含量是5.12μmol/g.这就形成了一种具有类似细胞外基质的新型仿生材料. 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
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Steffen Müller-Probandt 《材料科学与工程:中英文B版...》2018,(4):161-177
We associate a variety of innovations with the term "Industry 4.0". The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di... 相似文献
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On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
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Janet Lang 《Materials and Manufacturing Processes》2017,32(7-8):857-866
ABSTRACTThe production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them. 相似文献
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Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß. 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill. 相似文献
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Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ... 相似文献