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  • SAGE Publications  (6)
  • 1
    Online Resource
    Online Resource
    Soluble copolyimides containing 4,4′-isopropylidenedicyclohexanol (HBPA) isomer units: Synthesis, characterization, thermal, mechanical, and optical properties
    SAGE Publications ; 2020
    In:  High Performance Polymers Vol. 32, No. 4 ( 2020-05), p. 406-417
    Details
    In: High Performance Polymers, SAGE Publications, Vol. 32, No. 4 ( 2020-05), p. 406-417
    Abstract: In this work, 4,4′-isopropylidenedicyclohexanol (HBPA)-based dinitro isomers mixture (H″BPBN and H′BPBN) was synthesized and separated, and the structures of dinitro isomers were confirmed by differential scanning calorimetry and proton nuclear magnetic resonance spectroscopy. A series of copolyimides were prepared from diamino monomers with different percentages of novel diamine H″BPDA and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride via a conventional two-step procedure. All the copolyimides could afford flexible, tough, and transparent films with transmittance no less than 73% at 450 nm, which was attributed to the fact that nonplanar alicyclic diamine and the bulky and weakly polarizable trifluoromethyl hampered the formation of charge-transfer complex. Moreover, all the copolyimides were soluble not only in polar solvents such as N,N-dimethylformamide but also in low-boiling-point solvents such as dichloromethane, which was related to the fact that the existence of alicyclic diamine and bulky trifluoromethyl decreased the intermolecular force. In addition, the conformation effects of H″BPDA and H′BPDA on the aspects of thermal, mechanical, optical, and soluble performance of copolyimides were investigated and their structure–property relationships were discussed in detail.
    Type of Medium: Online Resource
    ISSN: 0954-0083 , 1361-6412
    URL: Article
    DOI: 10.1177/0954008319868001
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2020
    detail.hit.zdb_id: 1483713-4
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  • 2
    Online Resource
    Online Resource
    Comparison of airborne bacteria and fungi in different types of buildings in a temperate climate zone city, Kunming, China
    SAGE Publications ; 2022
    In:  Indoor and Built Environment Vol. 31, No. 7 ( 2022-08), p. 1949-1962
    Details
    In: Indoor and Built Environment, SAGE Publications, Vol. 31, No. 7 ( 2022-08), p. 1949-1962
    Abstract: The characteristics of airborne bacteria and fungi in different types of buildings are still unclear. This article applied the culturing and next-generation sequencing methods to characterize the airborne bacteria and fungi in five types of buildings during winter in Kunming, China. Results showed that the mean concentrations of fungi in different buildings were similar (approx. 387 ± 388 CFU/m 3 ). The highest culturable bacterial concentration was found in residences, while the lowest was in the library. Lowering relative humidity, PM 2.5 concentration and occupant density can reduce the bacterial concentrations. The major bacterial size in residences and in a hospital was 1.1–2.1 μm, while in other buildings was 2.1–3.3 μm. The PM 2.5 concentration and occupant activities are key factors that could affect the microorganism size distributions . The community structures of the bacteria in the library and fungi in the hospital showed distinctive differences from the results in other buildings. The community structure of outdoor microorganisms showed great differences between soil and air samples. This study is helpful to give practical implications for assessing microbial characteristics in different types of buildings and provide valuable data for the formulation of indoor bioaerosol standards in China.
    Type of Medium: Online Resource
    ISSN: 1420-326X , 1423-0070
    URL: Article
    DOI: 10.1177/1420326X221082198
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2022
    detail.hit.zdb_id: 1482713-X
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  • 3
    Online Resource
    Online Resource
    Exploring optimum power unit of propulsion system for high altitude airship
    SAGE Publications ; 2015
    In:  Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering Vol. 229, No. 2 ( 2015-02), p. 301-311
    Details
    In: Proceedings of the Institution of Mechanical Engineers, Part G: Journal of Aerospace Engineering, SAGE Publications, Vol. 229, No. 2 ( 2015-02), p. 301-311
    Abstract: Different schemes of a propulsion system have a distinguished influence on the overall performance of high altitude airship. There is an optimum power, called optimum power unit, to achieve the lowest propulsion system and energy system weight for a high altitude airship. The paper represents an optimization model of the optimum power unit for a high altitude airship. Firstly, the optimal Latin hypercube design method is applied to obtain the sample points of the distributed low power propulsion system. Secondly, the surrogate model, which is used to establish the optimization model, is obtained by responding surface method based on these sample points. The computational model of the energy system is obtained by the airship’s location and the working time. Finally, the multi-island genetic algorithm is used to find the optimum power unit for a typical high altitude airship. Furthermore, the optimization work under different typical power levels and diameters is carried out to verify the effectiveness of the optimum power unit design method. It has been found that the identical result validates the effectiveness of the optimum power unit design method.
    Type of Medium: Online Resource
    ISSN: 0954-4100 , 2041-3025
    URL: Article
    DOI: 10.1177/0954410014531741
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2015
    detail.hit.zdb_id: 2032759-6
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  • 4
    Online Resource
    Online Resource
    Creep of concrete-filled steel tube considering creep-recovery of the concrete core
    SAGE Publications ; 2020
    In:  Advances in Structural Engineering Vol. 23, No. 5 ( 2020-04), p. 997-1009
    Details
    In: Advances in Structural Engineering, SAGE Publications, Vol. 23, No. 5 ( 2020-04), p. 997-1009
    Abstract: Concrete creep results in the strain increment of concrete-filled steel tube. In this article, a new method was established for creep prediction of concrete-filled steel tube considering the creep-recovery effect of the concrete core with creep model and separate creep-recovery model, named two-function method. Five creep models including the recent proposed B4 model and two separate creep-recovery models were used in the method. First, the creep models were compared with 197 test curves of creep of sealed concrete. The results show that the B4 model offers the highest prediction accuracy for load duration time longer than 200 days. Then, the two-function method was used for creep prediction of normal strength concrete-filled steel tube and high-strength concrete-filled steel tube. For comparison, the creep prediction method for concrete-filled steel tube based on the principle of superposition was also adopted. The principle of superposition did not predict the creep of concrete-filled steel tube accurately. The calculation results based on the two-function method are closer to the test data, especially for normal strength concrete-filled steel tube. Finally, the uncertainty of creep in concrete-filled steel tube was analyzed considering the variability of the concrete strength. The results indicate that the variances calculated by the methods with the MC 2010 creep model are smaller than that of the B4 model. The creep strains of concrete-filled steel tube calculated by the two-function method are subject to normal distribution.
    Type of Medium: Online Resource
    ISSN: 1369-4332 , 2048-4011
    URL: Article
    DOI: 10.1177/1369433219886083
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2020
    detail.hit.zdb_id: 2026561-X
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  • 5
    Online Resource
    Online Resource
    Preparation and characterization of soluble heat-resistant polyimide films containing bis-N-phenyl-benzimidazole
    SAGE Publications ; 2022
    In:  High Performance Polymers Vol. 34, No. 2 ( 2022-03), p. 197-208
    Details
    In: High Performance Polymers, SAGE Publications, Vol. 34, No. 2 ( 2022-03), p. 197-208
    Abstract: To prepare soluble polyimides with high temperature resistance, two new diamine monomers, namely, 2,2 ′ -(4,4 ′ -oxybisphenylene)-bis(1-phenyl-5-aminobenzimidazole) (5a), and 2,2 ′ -(4,4 ′ -hexafluoroisopropylidene)-bis(1-phenyl-5- aminobenzimidazole) (5b), were synthesized and exploited to prepare three series of poly(benzimidazole imides)s (PBIIs) by a conventional two-stage synthesis. The resulting PI films were flexible and tough, possessing high glass-transition temperatures (T g s = 311°C–390°C), improved optical transparency, and excellent solubility. Moreover, the effect of different configuration on performance was revealed, and these data provided a feasible method to enhance both T g and solubility of PIs by incorporating N-phenyl benzimidazole and corresponding functional moieties.
    Type of Medium: Online Resource
    ISSN: 0954-0083 , 1361-6412
    URL: Article
    DOI: 10.1177/09540083211036326
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2022
    detail.hit.zdb_id: 1483713-4
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  • 6
    Online Resource
    Online Resource
    Exploring design of universal propeller simulator for airship propulsion system’s driving motor
    SAGE Publications ; 2014
    In:  Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering Vol. 228, No. 8 ( 2014-09), p. 612-620
    Details
    In: Proceedings of the Institution of Mechanical Engineers, Part I: Journal of Systems and Control Engineering, SAGE Publications, Vol. 228, No. 8 ( 2014-09), p. 612-620
    Abstract: Rare earth permanent magnet brushless direct current motor is the energy conversion device between power system and propeller of high-altitude airship. Its performance has a profound effect on the overall performance of the high-altitude airship. Limited by the output torque of the permanent magnet brushless direct current motor, propeller on the ground cannot reach the rated angular speed when propeller works at high altitude, so it is difficult to carry on rotation test on the ground. In addition, performances of the permanent magnet brushless direct current motor system such as control accuracy, reliability and efficiency cannot be tested. The functional level of the motor load simulator is proposed considering the dynamic properties of the propeller and the basic functions of the propulsion system. Different loading actuators are evaluated and the conceptual design of the load simulator is accomplished. Inertia is realized by relatively small flywheel and inertia electrical emulation method. Torque is simulated by servo motor that can work at braking state and thrust is exerted on the motor by hydraulic servo valve control system. Finally, depending on the proposed scheme and design parameters, co-simulation model of the load simulator is established utilizing software MATLAB/Simulink and AMESim. After comparing co-simulation results with real propeller properties, the feasibility of the conceptual design of permanent magnet brushless direct current motor load simulator is proved, and what is more, the effectiveness of control strategies and the rationality of parameters settings for co-simulation are testified.
    Type of Medium: Online Resource
    ISSN: 0959-6518 , 2041-3041
    URL: Article
    DOI: 10.1177/0959651814531253
    Language: English
    Publisher: SAGE Publications
    Publication Date: 2014
    detail.hit.zdb_id: 2024903-2
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