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温度 3

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Phase separation time/temperature dependence of thermoplastics-modified thermosetting systems

ZHANG Xiujuan, XU Yuanze, YI Xiaosu

《化学科学与工程前沿（英文）》 2008年第2卷第3期页码 276-285 doi: 10.1007/s11705-008-0057-5

摘要： The cure-induced phase separation processes of various thermoplastics(TP)-modified thermosetting systems which show upper critical solution temperature (UCST) or lower critical solution temperature (LCST) were studied with emphasis on the temperature dependency of the phase separation time and its potential application in the cure time-temperature processing window. We found that the phase separation time/temperature relationship follows the simple Arrhenius equation. The cure-induced phase separation activation energy (ps) generated from the linear fitting of the Arrhenius equation is irrelevant to the detection means of phase separation time. We also found that (ps) is insensitive to TP content, TP molecular weight and curing rate, but it changes with the cure reaction kinetics and the chemical environment of the systems. With the established phase separation time-temperature dependence relation, we can easily establish the whole cure time-temperature transformation (TTT) diagram with morphology information which is a useful map for the TP/TS composites processing industry.

关键词： separation time-temperature temperature dependency cure-induced separation activation temperature

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Fault evolution-test dependency modeling for mechanical systems

Xiao-dong TAN,Jian-lu LUO,Qing LI,Bing LU,Jing QIU

《信息与电子工程前沿（英文）》 2015年第16卷第10期页码 848-857 doi: 10.1631/FITEE.1500011

摘要： Tracking the process of fault growth in mechanical systems using a range of tests is important to avoid catastrophic failures. So, it is necessary to study the design for testability (DFT). In this paper, to improve the testability performance of mechanical systems for tracking fault growth, a fault evolution-test dependency model (FETDM) is proposed to implement DFT. A testability analysis method that considers fault trackability and predictability is developed to quantify the testability performance of mechanical systems. Results from experiments on a centrifugal pump show that the proposed FETDM and testability analysis method can provide guidance to engineers to improve the testability level of mechanical systems.

关键词： Mechanical systems Design for testability (DFT) Fault evolution-test dependency model (FETDM)

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Analysis and countermeasures of natural gas development in China

Wenzhi ZHAO, Ailin JIA, Guosheng ZHANG

《工程管理前沿（英文）》 2019年第6卷第4期页码 477-484 doi: 10.1007/s42524-019-0064-x

摘要： Natural gas has become a transitional bridge from fossil to green and clean energy worldwide. The importance of natural gas utilization in energy structure optimization and green development is no exception for China. However, the supply of China’s natural gas limits the country’s demand with three factors. (1) China’s natural gas resource is relatively rich, but its quality is poor with deep burial depth. Therefore, the annual plateau yield of natural gas cannot be high, with an estimated value of approximately 260–270 ×10 m . (2) The demand for natural gas in China’s economic development is growing rapidly. The peak demand is estimated to be approximately 550–650 ×10 m per year or even higher. The import volume of natural gas will soon exceed that of domestic self-produced gas. (3) Natural gas is a necessity closely related to livelihood. Particularly, a shortage in natural gas supply affects social stability. Therefore, its external dependency should be under 50% and not exceed 60%. In this study, the future situation of China’s natural gas is forecasted, and relevant countermeasures and suggestions are proposed in accordance with research on China’s natural gas resource potential, production trend, supply-demand link, and gas supply safety factors.

关键词： natural gas yield consumption external dependency security situation

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基于依存关系和多义词分析的句法词嵌入 None

Zhong-lin YE, Hai-xing ZHAO

《信息与电子工程前沿（英文）》 2018年第19卷第4期页码 524-535 doi: 10.1631/FITEE.1601846

摘要：现有大多数词嵌入学习模型存在以下问题：（1）基于词袋上下文的模型完全忽略句子的句法结构关系；（2）每个词使用单个嵌入向量使多义词共享一个嵌入向量；（3）词嵌入往往趋向于句子上下文共性。为解决这些问题，提出一种基于依存关系和多义词分析的句法词嵌入（syntactic word embedding, SWE）。该算法主要处理：（1）基于主题模型，提出一个多义词识别算法；（2）采用符号“+”和“−”表示依存关系方向；（3）删除停用词及其依存关系；（4）引入“skip”依存关系表示依存关系之间的间接关系；（5）将基于依存关系的上下文输入到Word2Vec模型中训练语言模型。实验结果表明，SWE模型在词相似度评测任务中表现出优异性能。基于依存关系句法上下文捕获词语的语义和句法特征，使词语表现出较少的上下文主题相似性和更多的句法和语义相似性。综上，包含更多信息的SWE模型性能优于单一的词嵌入学习模型。

关键词：基于依存关系的上下文；多义词表示；表示学习；句法词向量

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Axisymmetric loading on nanoscale multilayered media

《结构与土木工程前沿（英文）》 2023年第17卷第1期页码 152-164 doi: 10.1007/s11709-022-0895-0

摘要： Multilayered nanoscale structures are used in several applications. Because the effect of surface energy becomes nontrivial at such a small scale, a modified continuum theory is required to accurately predict their mechanical behaviors. A Gurtin–Murdoch continuum model of surface elasticity is implemented to establish a computational scheme for investigating an elastic multilayered system under axisymmetric loads with the incorporation of surface/interface energy. Each layer stiffness matrix is derived based on the general solutions of stresses and displacements obtained in the form of the Hankel integral transform. Numerical solutions to the global equation, which are formulated based on the continuity conditions of tractions and displacements across interfaces between layers, yield the displacements at each layer interface and on the top surface of the multilayered medium. The numerical solutions indicate that the elastic responses of multilayered structures are affected significantly by the surface material properties of both the top surface and interfaces, and that they become size dependent. In addition, the indentation problem of a multilayered nanoscale elastic medium under a rigid frictionless cylindrical punch is investigated to demonstrate the application of the proposed solution scheme.

关键词： functionally graded layer Gurtin–Murdoch surface elasticity multilayered medium size dependency stiffness matrix

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Dynamic failure analysis on granite under uniaxial impact compressive load

ZHAI Yue, MA Guowei, HU Changming, ZHAO Junhai

《结构与土木工程前沿（英文）》 2008年第2卷第3期页码 253-260 doi: 10.1007/s11709-008-0042-6

摘要： High strain-rate uniaxial compressive loading tests were produced in the modified split Hopkinson pressure bar (SHPB) with pulse shaper on granite samples. It was shown that the failure of the granite cylinder was typical tensile splitting failure mode by sudden splitting parallel to the direction of uniaxial compressive loading at different strain rates. Besides, it was concluded that not only the strength of granite increased, but also the fragment size decreased and the fragment numbers increased with the increasing strain rate. To quantitatively analyze the failure phenomena, the numerical calculation based on a dynamic interacting sliding microcrack model was adopted to investigate the influence of microcrack with the different initial crack length, crack angle, crack space and friction coefficient on the macro-mechanical properties of granite under different strain rates. Accordingly, the strain-dependency of the compression strength and the fragmentation degree of granite was explained reasonably.

关键词： numerical calculation coefficient cylinder splitting parallel strain-dependency

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Emerging challenges to structural integrity technology for high-temperature applications

TU Shantung

《机械工程前沿（英文）》 2007年第2卷第4期页码 375-387 doi: 10.1007/s11465-007-0066-y

摘要： Structural integrity technology has been widely used with great success for the design, manufacture and failure prevention of modern constructions such as chemical and petrochemical plants, power generation and energy conversion systems, as well as space and oceanic exploration. The modern needs of structural integrity technology are largely attributed to the increase of service temperature of the structures that results in the efficiency improvement in energy conversion and chemical processing technologies. Besides the needs arising from large-scale high-temperature plants, the high tech developments, such as micro chemo-mechanical systems and high-power electronics, provide new challenges to structural integrity technology. The present paper summarizes the recent technical progresses in large process plants and the aviation industry, micro chemo-mechanical systems, fuel cells, high-temperature electronics, and packaging and coating technologies. The state-of-the-art of structural integrity technology for high temperature applications is reviewed. Suggestions are provided for the improvement of current design and assessment methods.

关键词： manufacture aviation industry conversion petrochemical temperature

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Effects of temperature on pyrolysis products of oil sludge

LIU Jianguo, SONG Wei, NIE Yongfeng

《环境科学与工程前沿（英文）》 2008年第2卷第1期页码 8-14 doi: 10.1007/s11783-008-0030-z

摘要： Temperature is the determining factor of pyrolysis, which is one of the alternative technologies for oil sludge treatment. The effects of final operating temperature ranging from 350 to 550°C on pyrolysis products of oil sludge were studied in an externally-heating fixed bed reactor. With an increase of temperature, the mass fraction of solid residues, liquids, and gases in the final product is 67.00%–56.00%, 25.60%–32.35%, and 7.40%–11.65%, and their corresponding heat values are 34.4–13.8 MJ/kg, 44.41–46.6 MJ/kg, and 23.94–48.23 MJ/Nm, respectively. The mass and energy tend to shift from solid to liquid and gas phase (especially to liquid phase) during the process, and the optimum temperature for oil sludge pyrolysis is 500°C. The liquid phase is mainly composed of alkane and alkene (C–C), and the gas phase is dominantly HC and H.

关键词： sludge treatment corresponding Temperature liquid process

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Elevated temperature creep model of parallel wire strands

《结构与土木工程前沿（英文）》页码 1060-1071 doi: 10.1007/s11709-023-0981-y

摘要： Parallel wire strands (PWSs), which are widely used in prestressed steel structures, are typically in high-stress states. Under fire conditions, significant creep effects occur, reducing the prestress and influencing the mechanical behavior of PWSs. As there is no existing approach to analyze their creep behavior, this study experimentally investigated the elevated temperature creep model of PWSs. A charge-coupled camera system was incorporated to accurately obtain the deformation of the specimen during the elevated temperature creep test. It was concluded that the temperature level had a more significant effect on the creep strain than the stress level, and 450 °C was the key segment point where the creep rate varied significantly. By comparing the elevated temperature creep test results for PWSs and steel strands, it was found that the creep strain of PWSs was lower than that of steel strands at the same temperature and stress levels. The parameters in the general empirical formula, the Bailey–Norton model, and the composite time-hardening model were fitted based on the experimental results. By evaluating the accuracy and form of the models, the composite time-hardening model, which can simultaneously consider temperature, stress, and time, is recommended for use in the fire-resistance design of pre-tensioned structures with PWSs.

关键词： parallel wire strands experimental study elevated temperature creep model

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Field test on temperature field and thermal stress for prestressed concrete box-girder bridge

Baoguo CHEN, Rui DING, Junjie ZHENG, Shibiao ZHANG

《结构与土木工程前沿（英文）》 2009年第3卷第2期页码 158-164 doi: 10.1007/s11709-009-0002-9

摘要： A field test was conducted to investigate the distribution of temperature field and the variation of thermal stress for a prestressed concrete (PC) box-girder bridge. The change of hydration heat temperature consists of four periods: temperature rising period, constant temperature period, rapid temperature fall period and slow temperature fall period. The peak value of hydration heat temperature increases with the increasing casting temperature of concrete; the relation between them is approximately linear. According to field tests, the thermal stress incurred by hydration heat may induce temperature cracks on the PC box-girder. Furthermore, the nonlinear distribution of temperature gradient and the fluctuation of thermal stress induced by exposure to sunlight were also obtained based on continuous in-situ monitoring. Such results show that the prevailing Chinese Code (2004) is insufficient since it does not take into account the temperature gradient of the bottom slab. Finally, some preventive measures against temperature cracks were proposed based on related studies. The conclusions can provide valuable reference for the design and construction of PC box-girder bridges.

关键词： box-girder bridge field test hydration heat temperature field temperature gradient thermal stress

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A review of low-temperature plasma-assisted machining: from mechanism to application

《机械工程前沿（英文）》 2023年第18卷第1期 doi: 10.1007/s11465-022-0734-y

摘要： Materials with high hardness, strength or plasticity have been widely used in the fields of aviation, aerospace, and military, among others. However, the poor machinability of these materials leads to large cutting forces, high cutting temperatures, serious tool wear, and chip adhesion, which affect machining quality. Low-temperature plasma contains a variety of active particles and can effectively adjust material properties, including hardness, strength, ductility, and wettability, significantly improving material machinability. In this paper, we first discuss the mechanisms and applications of low-temperature plasma-assisted machining. After introducing the characteristics, classifications, and action mechanisms of the low-temperature plasma, we describe the effects of the low-temperature plasma on different machining processes of various difficult-to-cut materials. The low-temperature plasma can be classified as hot plasma and cold plasma according to the different equilibrium states. Hot plasma improves material machinability via the thermal softening effect induced by the high temperature, whereas the main mechanisms of the cold plasma can be summarized as chemical reactions to reduce material hardness, the hydrophilization effect to improve surface wettability, and the Rehbinder effect to promote fracture. In addition, hybrid machining methods combining the merits of the low-temperature plasma and other energy fields like ultrasonic vibration, liquid nitrogen, and minimum quantity lubrication are also described and analyzed. Finally, the promising development trends of low-temperature plasma-assisted machining are presented, which include more precise control of the heat-affected zone in hot plasma-assisted machining, cold plasma-assisted polishing of metal materials, and further investigations on the reaction mechanisms between the cold plasma and other materials.

关键词： low-temperature plasma difficult-to-cut material machinability hydrophilization effect Rehbinder effect

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Real-time tool condition monitoring method based on temperature measurement and artificial neural network

《机械工程前沿（英文）》 doi: 10.1007/s11465-021-0661-3

摘要： Tool failures in machining processes often cause severe damages of workpieces and lead to large quantities of loss, making tool condition monitoring an important, urgent issue. However, problems such as practicability still remain in actual machining. Here, a real-time tool condition monitoring method integrated in an in situ fiber optic temperature measuring apparatus is proposed. A thermal simulation is conducted to investigate how the fluctuating cutting heats affect the measuring temperatures, and an intermittent cutting experiment is carried out, verifying that the apparatus can capture the rapid but slight temperature undulations. Fourier transform is carried out. The spectrum features are then selected and input into the artificial neural network for classification, and a caution is given if the tool is worn. A learning rate adaption algorithm is introduced, greatly reducing the dependence on initial parameters, making training convenient and flexible. The accuracy stays 90% and higher in variable argument processes. Furthermore, an application program with a graphical user interface is constructed to present real-time results, confirming the practicality.

关键词： tool condition monitoring cutting temperature neural network learning rate adaption

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Effects of pressure and temperature on fixed-site carrier membrane for CO 2 separation from natural gas

Meng WANG, Dongxiao YANG, Zhi WANG, Jixiao WANG, Shichang WANG,

《化学科学与工程前沿（英文）》 2010年第4卷第2期页码 127-132 doi: 10.1007/s11705-009-0231-4

摘要： In this paper, the effect of testing temperature on the performance of fixed carrier membrane for CO separation were studied. The blend composite membranes were developed respectively with a blend of PEI-PVA (polyetheleneimine-polyvinyl alcohol) as separation layer and PS (polysulfone) ultrafiltration membranes as the substrates. The permselectivity of the membranes was measured with CO/CH mixed gas. The effect of testing temperature on membrane separation performance was investigated. The results showed that both the permeances of CO and CH decreased with the increase of temperature, and the permeances decreased more quickly under low pressure than those under high pressure. At the feed pressure of 0.11MPa, the CO/ CH selectivity of PEI-PVA/PS blend composite membrane reduced along with temperature increment. Under the feed pressure of 0.21MPa, as well as 1.11MPa, the selectivity decreased with the increase of temperature.

关键词： temperature increment high pressure permselectivity separation performance temperature

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Investigation on the performance and detoxification of modified low temperature coal tar pitch

Fengyan SUN, Yu LIU

《结构与土木工程前沿（英文）》 2017年第11卷第3期页码 315-321 doi: 10.1007/s11709-017-0386-x

摘要： In this paper, studies on the modification on the low temperature coal tar pitch extracted from coal tar residue in Inner Mongolia are conducted. First, the low temperature coal tar pitch in liquid state is solidified with a higher softening point by chemical crosslinking modification. The modified coal tar pitch can achieve the standard pavement performance requirements. Then, the effects of chemical crosslinking agent and physical modification additives on the mechanical performance and toxic properties of coal tar pitch are investigated. The detoxification mechanism is also studied, which further promote the applicability of modified low temperature coal tar pitch in the pavement constructions.

关键词： coal tar pitch low temperature modification detoxification

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A review on the development of electrolytes for lithium-based batteries for low temperature applications

《能源前沿（英文）》 2023年第17卷第1期页码 43-71 doi: 10.1007/s11708-022-0853-5

摘要： The aerospace industry relies heavily on lithium-ion batteries in instrumentation such as satellites and land rovers. This equipment is exposed to extremely low temperatures in space or on the Martian surface. The extremely low temperatures affect the discharge characteristics of the battery and decrease its available working capacity. Various solvents, cosolvents, additives, and salts have been researched to fine tune the conductivity, solvation, and solid-electrolyte interface forming properties of the electrolytes. Several different resistive phenomena have been investigated to precisely determine the most limiting steps during charge and discharge at low temperatures. Longer mission lifespans as well as self-reliance on the chemistry are now highly desirable to allow low temperature performance rather than rely on external heating components. As Martian rovers are equipped with greater instrumentation and demands for greater energy storage rise, new materials also need to be adopted involving next generation lithium-ion chemistry to increase available capacity. With these objectives in mind, tailoring of the electrolyte with higher-capacity materials such as lithium metal and silicon anodes at low temperatures is of high priority. This review paper highlights the progression of electrolyte research for low temperature performance of lithium-ion batteries over the previous several decades.

关键词： electrolyte lithium-ion low temperature aerospace solid-electrolyte interface