共查询到20条相似文献,搜索用时 140 毫秒
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近年来,世界各国均加大力度禁止和限制不易回收、易污染的一次性塑料产品。生物降解塑料成为替代一次性塑料产品的最佳选择。生物降解塑料分为生物基和石化基两大类。前者按制作方法细分为完全生物降解塑料(全淀粉生物降解塑料、微生物发酵和化学合成共同参与获得的生物降解塑料、微生物合成型生物降解塑料、共混型生物降解塑料)和不完全生物降解塑料。后者是以煤或石油等化石能源为原料,用化学合成法由单体聚合而成,代表性品种有聚丁二酸丁二酯(PBS)、聚己二酸对苯二甲酸丁二酯(PBAT)、聚碳酸亚丙酯(PPC)等,该类塑料均基于脂肪族聚酯,分子链上的酯基结构决定了它们易被微生物或酶降解。从上述各类生物降解塑料的加工制作方法、性能特点、应用场合以及全球、国内外产能状况展开论述。未来,我国应重点发展淀粉基、PLA、 PBAT等三大生物降解塑料,应重视对高分子设计法的研究。 相似文献
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<正> 生物降解塑料是指一类由自然界存在的微生物如细菌、霉菌(真菌)和藻类的作用而引起降解的塑料。理想的生物降解塑料是一种具有优良的使用性能、废弃后可被环境微生物完全分解、 相似文献
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生物降解包装塑料研究进展 总被引:3,自引:1,他引:2
生物降解包装塑料是一种绿色包装塑料,生物降解法是一种很好解决废弃包装塑料的新方法.介绍了生物降解包装塑料的种类,分析了生物降解包装塑料的机理,综述了生物降解包装塑料的研究进展,指出了生物降解包装塑料的发展趋势. 相似文献
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K. V. Frolov N. A. Makhutov G. Kh. Khurshudov M. M. Gadenin 《Strength of Materials》2000,32(5):409-416
The evolution of approaches to the solution of machine dynamics and strength problems on the basis of determining static and dynamic nominal and local stresses of the operating load is discussed. It is shown how the material strength and plasticity characteristics, the cyclic strength characteristics in the high-cycle and low-cycle fatigue regions, the high-temperature long-term strength and creep characteristics, and the linear and nonlinear characteristics of fracture mechanics were sequentially used as the basic criterial parameters of the deformability and strength of structural materials. Particular emphasis was given to the results of studies on machine safety and catastrophe mechanics. Integrated approaches to the solution of strength and safety problems of potentially dangerous facilities (nuclear power stations, spacecraft complexes, aircraft, chemical plants, etc.) by analysis of all stages of their life cycle, including design, manufacture, testing, and operation, are discussed. 相似文献
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本文是作者再次对标准和标准化的概念进行讨论。首先讨论的是标准化的目的、主体和对象。作者认为标准化的目的是控制、有序化和统一化;标准化的主体是人/机构;标准化对象可以是具体的或抽象的事物,也可以是它们的组合;任何事物都可以抽象地表达为实体(entity)。第二,作者讨论了标准和标准化的本质以及它们的作用;认为从内容角度看,标准是匹配问题解决方案,也是为标准化对象规定需要满足的要求;从实施角度看,标准是规则;标准化则是制定、实施、传播标准的过程;标准的作用是能够创建并组织现实世界,并能够为相关方建立互相交流和共同理解的基础;标准化的作用是对创新方案进行选择和简化,阻止现实世界过度无序化发展,形成复杂化和简化之间的平衡。第三,作者讨论了标准的记录形式、自愿/强制属性和时空范围,认为标准的记录形式有文件、样品、图形符号、物理表达等多种形式;标准具有选择的自愿性和实施的强制性;标准在时空范围内是有限的。文章的结尾给出了理解标准化概念的框架。 相似文献
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由于工作环境复杂多变,制动器工作不稳定而导致振动和噪声,鼓式制动器制动时的温度变化对制动不稳定性影响较大,研究制动不稳定性影响因素及其制动不稳定时变特性具有实际工程意义。基于鼓式制动器四自由度接触模型,分别在Hypermesh和ABAQUS中建立鼓式制动器制动鼓和制动蹄总成模型与摩擦制动接触模型并进行试验验证;通过热机耦合动态分析,研究制动鼓温度对制动应力的影响;分析弹性模量和热膨胀系数对鼓式制动器制动不稳定时变特性的影响。分析表明:制动不稳定性是摩擦力耦合所致;制动过程中制动鼓温度与应力相互作用且均先快速上升后缓慢下降;鼓式制动器制动不稳定时变特性主要体现在不稳定模态个数及不稳定倾向系数(tendency of instability, TOI)值的变化,制动温度变化导致弹性模量变化,引起不稳定模态个数和TOI值略有变化,弹性模量对鼓式制动器制动不稳定时变特性影响较小;制动温度变化导致热膨胀系数变化,引起不稳定模态个数和TOI值先大幅降低后略有升高,热膨胀系数对鼓式制动器制动不稳定时变特性影响较大。研究结果对改善汽车制动声品质具有一定指导意义。 相似文献
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目的 介绍了用最小二乘法评价线性测量系统性度、直流增益和直流偏移几项指标时,测量结果的不确定度分析和评价过程。方法 讨论了影响评价结果不确定度的几个主要误差来源,包括信号源误差、被校系统测量误差、被校系统增益影响、量程范围内输入信号数值个数、环境影响等等,给出了减小线性度、直流增益和直流偏移几项指标评价不确定度的主要措施:(1)环境控制措施,以减少环境带来的不确定度;(2)选取高精度信号,以减少信 相似文献
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A mathematical model was presented to describe the particle trajectory, velocity and temperature properties in the low power plasma spraying torch (3.6 kW)in which powder particles were directly injected into the region between the cathode and anode. The results show that the characteristics of the particles by low power plasma spraying are similar to that by traditional APS( Atmosphere plasma spraying) in 40 kW. The velocities of the particles increase with the increase of inlet gas flow rate, current and percentage of nitrogen and hydrogen, while the temperature of the powder increase with the decrease of the gas flow rate and with the increase of current and percentage of nitrogen and hydrogen. 相似文献
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R.U. Abdurakhmanov R.M. Saidov U. Semmler K.‐J. Matthes A.R. Abdurakhmanov M.G. Aitureev A.R. Bohr 《Materialwissenschaft und Werkstofftechnik》2004,35(6):385-393
Investigation of melting and re‐crystallization processes and of crack, oxide and pore formation during welding In the paper some known investigation methods of the primary re‐crystallization and of the structure of the crystallization front are discussed. All these methods have disadvantages, in some cases they cause a limited validity or are expensive. The presented new method is based on the micrographic recording of the melting and solidifying metal surfaces. The method overcomes the above‐mentioned disadvantages. It is able to investigate in the welding seams not only the primary re‐crystallization processes but also the secondary ones including the formation of cracks and pores and the appearance of non‐metallic inclusions like oxides. The facilities of the method are demonstrated on some examples of use. 相似文献
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提出用贝叶斯-GO综合方法分析快递配送系统可靠性。首先综合考虑配送系统对时间、品质、服务可靠性的要求,详细分析配送工作流程及其影响因素,建立GO图;然后根据映射规则转换为贝叶斯网络,最后通过案例分析,利用贝叶斯网络正反向推理和敏感度分析,得到系统的薄弱环节及其主要影响因素。研究结果表明:贝叶斯-GO综合法克服了单独使用GO法逻辑运算复杂繁琐的缺点,能够快速找到快递配送系统的薄弱环节及其主要影响因素,其中收件子系统故障率最高,快递员的配送不及时、寄件损坏、丢失是主要影响因素。 相似文献
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目的 探索江门世遗文化的传承、发展和转化的新思路,践行国家在《粤港澳大湾区发展规划》纲要中要求江门承担与港澳地区文化创意合作与开发任务的分工。方法 与澳门高校紧密合作,开展专业培训课程,以开平碉楼为例,从人文视角开展设计研究,梳理开平碉楼的文化脉络,把世遗文化的元素和其背后的文化融入文创产品中,提升文创产品的附加值,推动当地文创产业结构的变革。结果 两地高校构建了稳定的科研团队,开设长期有效的设计培训课程,与景区建立了研究协作关系,帮助景区构建了一套产销研的商业模式。结论 以跨区域高校合作为平台,以文创产品为抓手,依托江澳两地的资源优势,可以构建江门世遗文化全新的品牌形象,最终推动开平世遗文化的活化。 相似文献
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The active thermal potentiostatting system proposed by Martinovskii and Tsirlin is directly generalized to a more practical case, in which one intermediate chamber, besides a thermal potentiostatting chamber, and two irreversible refrigeration cycles are included and the influence of the thermal resistance between the working fluid and the reservoirs, the heat leakages from the environment to the intermediate chamber and from the intermediate chamber to the potentiostatting chamber are taken into account. Expressions for the main parameters of the system are derived. By using the optimal control theory, the minimum total power input of the system with non-zero cooling rates is calculated and the temperatures of the working fluid in the isothermal processes of the refrigeration cycles are optimized. The optimal allocation of the heat-transfer areas of the heat-exchangers in the refrigeration cycles is discussed in detail. The results obtained here are more general and useful than the relevant results in literature and can provide some valuable guidance for the optimal design and operation of real active thermal potentiostatting systems. 相似文献