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Influence factors on natural frequencies of composite materials

Bo WANG, Feng ZHAO, Zixu ZHAO, Kunpeng XU

《机械工程前沿（英文）》 2020年第15卷第4期页码 571-584 doi: 10.1007/s11465-020-0592-4

摘要： Compared with traditional materials, composite materials have lower specific gravity, larger specific strength, larger specific modulus, and better designability structure and structural performance. However, the variability of structural properties hinders the control and prediction of the performance of composite materials. In this work, the Rayleigh–Ritz and orthogonal polynomial methods were used to derive the dynamic equations of composite materials and obtain the natural frequency expressions on the basis of the constitutive model of laminated composite materials. The correctness of the analytical model was verified by modal hammering and frequency sweep tests. On the basis of the established theoretical model, the influencing factors, including layers, thickness, and fiber angles, on the natural frequencies of laminated composites were analyzed. Furthermore, the coupling effects of layers, fiber angle, and lay-up sequence on the natural frequencies of composites were studied. Research results indicated that the proposed method could accurately and effectively analyze the influence of single and multiple factors on the natural frequencies of composite materials. Hence, this work provides a theoretical basis for preparing composite materials with different natural frequencies and meeting the requirements of different working conditions.

关键词： composite material hammering and frequency sweep test structural parameter natural frequency

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An investigation into the vibration of harmonic drive systems

M. Masoumi, H. Alimohammadi

《机械工程前沿（英文）》 2013年第8卷第4期页码 409-419 doi: 10.1007/s11465-013-0275-5

摘要：

Harmonic drive systems are precise and specific transmission gear systems which are beneficial in terms of the high transmission ratio and almost zero backlash. These inherent and spectacular properties result in using this mechanism in robotic and space sciences where the precision and lightwieght play an important role. This paper presents a vibration analysis of harmonic drive systems using the shell theory. Equations of vibration for the flexspline and the circular spline of the system are derived and used to find the natural frequencies for both parts and, moreover, vibration response of the system under the operating condition is calculated. Also, obtained vibration equations are utilized to study the effects of different involved parameters such as the geometry of the flexspline and its gear tooth, eccentricity, and unbalancing on the vibrational behavior of the system.

关键词： harmonic drive system strain wave gearing mechanism vibration analysis natural frequencies

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Vibration analysis of multi-walled carbon nanotubes embedded in elastic medium

Pattabhi R. BUDARAPU,Sudhir Sastry YB,Brahmanandam JAVVAJI,D. Roy MAHAPATRA

《结构与土木工程前沿（英文）》 2014年第8卷第2期页码 151-159 doi: 10.1007/s11709-014-0247-9

摘要： We propose a method to estimate the natural frequencies of the multi-walled carbon nanotubes (MWCNTs) embedded in an elastic medium. Each of the nested tubes is treated as an individual bar interacting with the adjacent nanotubes through the inter-tube Van der Waals forces. The effect of the elastic medium is introduced through an elastic model. The mathematical model is finally reduced to an eigen value problem and the eigen value problem is solved to arrive at the inter-tube resonances of the MWCNTs. Variation of the natural frequencies with different parameters are studied. The estimated results from the present method are compared with the literature and results are observed to be in close agreement.

关键词： natural frequencies multi-walled carbon nanotubes (MWCNTS) elastic medium

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Frequencies of circular plate with concentric ring and elastic edge support

null

《机械工程前沿（英文）》 2014年第9卷第2期页码 168-176 doi: 10.1007/s11465-014-0299-5

摘要：

Exact solutions for the flexural vibrations of circular plates having elastic edge conditions along with rigid concentric ring support have been presented in this paper. Values of frequency parameter for the considered circular plate are computed for different sets of values of elastic rotational and translation restraints and the radius of internal rigid ring support. The results for the first three modes of plate vibrations are computed and are presented in tabular form. The effects of rotational and linear restraints and the radius of the rigid ring support on the vibration behavior of circular plates are studied over a wide range of non-dimensional parametric values. The values of the exact frequency parameter presented in this paper for varying values of restraint parameters and the radius of the rigid ring support can better serve in design and as benchmark solutions to validate the numerical methods obtained by using other methods of solution.

关键词： circular plate frequency elastic edge rigid ring mode switching

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Research on the theory and application of adsorbed natural gas used in new energy vehicles: A review

Zhengwei NIE,Yuyi LIN,Xiaoyi JIN

《机械工程前沿（英文）》 2016年第11卷第3期页码 258-274 doi: 10.1007/s11465-016-0381-2

摘要：

Natural gas, whose primary constituent is methane, has been considered a convincing alternative for the growth of the energy supply worldwide. Adsorbed natural gas (ANG), the most promising methane storage method, has been an active field of study in the past two decades. ANG constitutes a safe and low-cost way to store methane for natural gas vehicles at an acceptable energy density while working at substantially low pressures (3.5–4.0 MPa), allowing for conformable store tank. This work serves to review the state-of-the-art development reported in the scientific literature on adsorbents, adsorption theories, ANG conformable tanks, and related technologies on ANG vehicles. Patent literature has also been searched and discussed. The review aims at illustrating both achievements and problems of the ANG technologies-based vehicles, as well as forecasting the development trends and critical issues to be resolved of these technologies.

关键词： adsorbed natural gas (ANG) adsorbent adsorption theory conformable tank natural gas vehicles (NGVs)

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Effects of natural zeolite and sulfate ions on the mechanical properties and microstructure of plastic

《结构与土木工程前沿（英文）》 2022年第16卷第1期页码 86-98 doi: 10.1007/s11709-021-0793-x

摘要： One of the strategic materials used in earth-fill embankment dams and in modifying and preventing groundwater flow is plastic concrete (PlC). PlC is comprised of aggregates, water, cement, and bentonite. Natural zeolite (NZ) is a relatively abundant mineral resource and in this research, the microstructure, unconfined strength, triaxial behavior, and permeability of PlC made with 0%, 10%, 15%, 20%, and 25% replacement of cement by NZ were studied. Specimens of PIC-NZ were subjected to confined conditions and three different confining pressures of 200, 350, and 500 kPa were used to investigate their mechanical behavior and permeability. To study the effect of sulfate ions on the properties of PlC-NZ specimens, the specimens were cured in one of two different environments: normal condition and in the presence of sulfate ions. Results showed that increasing the zeolite content decreases the unconfined strength, elastic modulus, and peak strength of PlC-NZ specimens at the early ages of curing. However, at the later ages, increasing the zeolite content increases unconfined strength as well as the peak strength and elastic modulus. Specimens cured in the presence of sulfate ions indicated lower permeability, higher unconfined strength, elastic modulus, and peak strength due to having lower porosity.

关键词： plastic concrete sulfate resistance natural zeolite triaxial compression test SEM permeability

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A review on technologies with electricity generation potentials using liquified natural gas regasification

《能源前沿（英文）》 2023年第17卷第3期页码 332-379 doi: 10.1007/s11708-023-0863-y

摘要： In modern times, worldwide requirements to curb greenhouse gas emissions, and increment in energy demand due to the progress of humanity, have become a serious concern. In such scenarios, the effective and efficient utilization of the liquified natural gas (LNG) regasification cold energy (RCE), in the economically and environmentally viable methods, could present a great opportunity in tackling the core issues related to global warming across the world. In this paper, the technologies that are widely used to harness the LNG RCE for electrical power have been reviewed. The systems incorporating, the Rankine cycles, Stirling engines, Kalina cycles, Brayton cycles, Allam cycles, and fuel cells have been considered. Additionally, the economic and environmental studies apart from the thermal studies have also been reviewed. Moreover, the discussion regarding the systems with respect to the regassification pressure of the LNG has also been provided. The aim of this paper is to provide guidelines for the prospective researchers and policy makers in their decision making.

关键词： liquified natural gas cold energy power generation

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Accelerating the construction of natural gas system engineering in green smart cities

Xinhua MA

《工程管理前沿（英文）》 2019年第6卷第3期页码 453-456 doi: 10.1007/s42524-019-0046-z

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New nanostructured sorbents for desulfurization of natural gas

Lifeng WANG, Ralph T. YANG

《化学科学与工程前沿（英文）》 2014年第8卷第1期页码 8-19 doi: 10.1007/s11705-014-1411-4

摘要： Desulfurization of natural gas is achieved commercially by absorption with liquid amine solutions. Adsorption technology could potentially replace the solvent extraction process, particularly for the emerging shale gas wells with production rates that are generally lower than that from the large conventional reservoirs, if a superior adsorbent (sorbent) is developed. In this review, we focus our discussion on three types of sorbents: metal-oxide based sorbents, Cu/Ag-based and other commercial sorbents, and amine-grafted silicas. The advantages and disadvantages of each type are analyzed. Possible approaches for future developments to further improve these sorbents are suggested, particularly for the most promising amine-grafted silicas.

关键词： desulfurization natural gas desulfurization hydrogen sulfide sorbent amine-silica sorbent

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Dehydration of natural gas and biogas streams using solid desiccants: a review

Soheil Bahraminia, Mansoor Anbia, Esmat Koohsaryan

《化学科学与工程前沿（英文）》 2021年第15卷第5期页码 1050-1074 doi: 10.1007/s11705-020-2025-7

摘要： Natural gas and biogas are two mixtures that consist of methane as their main component. These two gas mixtures are usually saturated with water vapor, which cause many problems, such as damaging the gas processing equipment by increasing the gas’s corrosion potential or clogging the pipelines due to gas hydrate formation. Thus, removing water vapor from these gas streams is mandatory. In this review paper, the main dehydration methods have been overviewed, and scrutiny of the adsorption dehydration has been carried out. Furthermore, the most important solid desiccants and their improvements have been reviewed.

关键词： natural gas biogas dehydration adsorption solid desiccant

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2019 highlights of the structural revision of natural product

Zongjia Chen, Mark A. Rizzacasa

《化学科学与工程前沿（英文）》 2021年第15卷第3期页码 595-601 doi: 10.1007/s11705-020-1971-4

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我国西部天然气东输的可行性

邱中建

《中国工程科学》 1999年第1卷第1期页码 94-98

摘要：

我国西部天然气资源十分丰富，占全国天然气总资源量的75%、探明储量的80%，已累计探明储量达13 110×10⁸m³,西部地区已有能力长期稳定年外输气150×10⁸m³。西气东输塔里木天然气有决定意义，目前正在评价的新发现的两个大型气田预计可迅速新增天然气探明储量约5 000×10⁸m³。这些气田储量丰度大，单井产量高，采气成本低。东部长江三角洲地区经济发达，能源短缺，自给率仅为13%，目前能源消费构成中煤炭占76%，城市环境污染严重，是天然气消费的巨大市场。预计2010年天然气需要量253×10⁸m³。西气东输有两个方案，一是塔里木气单独东输，开始年输量100×10⁸m³，第八年开始增加至150×10⁸m³；二是西部诸盆地联合东输，开始年输量150×10⁸m³，第八年开始增加至230×10⁸m³。两个方案均有经济效益，以联合东输方案优点较多。天然气在上海门站每立方米的销售价为1.2～1.3元，是很有竞争力的。项目一旦启动，对东部及西部地区均会带来巨大的好处。

关键词：西部天然气东输可行性

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Mechanisms for simultaneous ozonation of sulfamethoxazole and natural organic matters in secondary effluent

《环境科学与工程前沿（英文）》 2021年第15卷第4期 doi: 10.1007/s11783-020-1368-0

摘要：

• SMX was mainly degraded by hydrolysis, isoxazole oxidation and double-bond addition.

关键词： Sulfamethoxazole Ozonation Natural organic matters Secondary effluent Degradation mechanism

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Mesoporous zeolites as efficient catalysts for oil refining and natural gas conversion

Jie ZHU, Xiangju MENG, Fengshou XIAO

《化学科学与工程前沿（英文）》 2013年第7卷第2期页码 233-248 doi: 10.1007/s11705-013-1329-2

摘要： Zeolites have been regarded as one of the most important catalysts in petrochemical industry due to their excellent catalytic performance. However, the sole micropores in zeolites severely limit their applications in oil refining and natural gas conversion. To solve the problem, mesoporous zeolites have been prepared by introducing mesopores into the zeolite crystals in recent years, and thus have the advantages of both mesostructured materials (fast diffusion and accessible for bulky molecules) and microporous zeolite crystals (strong acidity and high hydrothermal stability). In this review, after giving a brief introduction to preparation, structure, and characterization of mesoporous zeolites, we systematically summarize catalytic applications of these mesoporous zeolites as efficient catalysts in oil refining and natural gas conversion including catalytic cracking of heavy oil, alkylation, isomerization, hydrogenation, hydrodesulfurization, methane dehydroaromatization, methanol dehydration to dimethyl ether, methanol to olefins, and methanol to hydrocarbons.

关键词： mesoporous zeolite catalysis oil refining natural gas conversion

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Approach for natural gas to be a primary energy source in China

Weihe HUANG, Jindian CHEN, Chuan FU, Yan HUANG

《工程管理前沿（英文）》 2019年第6卷第4期页码 467-476 doi: 10.1007/s42524-019-0068-6

摘要： This work reveals the positioning of natural gas in the evolution of world energy and the general law of its development. In the long-term adjustment of energy structure, natural gas has gradually become the primary energy source because of five factors: policy, resources, technology, facilities, and market. To expedite the revolution of energy production and consumption, China must urgently expand the use of natural gas toward a more positive role in complementing coal and renewable energy and prioritize its usage in three areas, namely, urban gas, power generation, and industrial fuel. Natural gas is expected to account for approximately 15% of China’s total energy consumption in the future. For natural gas to be the primary energy, the exploitation of gas resources must be expanded, resource access must be improved, a flexible trade system must be set up, infrastructure investment must be increased, and the security system must be enhanced.

关键词： natural gas energy revolution primary energy utilization areas approaching means