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Study on the mechanical properties of a type of spherical bearing

Yang Yingfang, Zhang Yan, Ju Jinsan

Journal of Theoretical and Applied Mechanics

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2021

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Vol. 59 nr 4

539--550

EN

The spherical bearing is widely used in highways, bridges and long-span structures. In order to study mechanical properties of a large-scale spherical bearing, a full-scale finite element model of the spherical bearing was established by using ABAQUS software, and the mechanical properties of the spherical bearing under four working conditions were simulated respectively when the upper bearing plate had different inclination angles. The ultimate bearing capacity of the spherical bearing under vertical tension was analyzed emphatically. The research results show that, in practical applications, the change in bearing capacity caused by the inclination angle of the upper bearing plate should be considered, and the wedge-shaped part should be strengthened.

2

Effects of Metal Oxides on the Thermal Decomposition Kinetics and Mechanisms of HAN/PVA Based Propellants

Hu Song-qi, Liu Xue-li, Liu Lin-Lin, Kang Bo, Zhang Yan

Central European Journal of Energetic Materials

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2021

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Vol. 18, no. 3

322-338

EN

The thermal decomposition processes of HAN/PVA-based propellants have been investigated using a simultaneous thermogravimetric analysis (TGA) – differential scanning calorimetry (DSC), coupled with Fourier-Transform Infrared Spectroscopy (FTIR) and Mass Spectrometry (MS) system. The activation energy (Ea), pre-exponential factor A and reaction mechanism function f(α) of the decomposition processes have been determined by non-isothermal and Malek methods. The results showed that the decomposition process of an HAN/PVA sample occurs mainly in the temperature range 202.2~220.1 °C, with a mass loss, heat release and Ea of about 84.8%, 1474.18 and 88.76 kJ·mol–1, respectively. Of the seven metal oxides studied as catalysts, Al2O3, V2O5 and Fe2O3 have significant catalytic effects on an HAN/PVA-based propellant, in lowering the decomposition temperature, with Ea changing from 88.8 to 83.7, 85.6 and 113.6 kJ·mol–1, respectively. The f(α) of both HAN/PVA and HAN/PVA/Al2O3 samples can be expressed as f(α) = (1 – α)2, whereas f(α) = α or f(α) = α/2 fit well for the HAN/PVA/V2O5 and HAN/PVA/Fe2O3 samples.

3

Sensory characteristics analysis for typical odor emission sources

Yan Fengyue, Li Weifang, Wang Gen, Geng Jing, Lu Zhiqiang, Zhai Zengxiu, Zhang Yan

Archives of Environmental Protection

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2021

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Vol. 47, no. 3

92--97

EN

The hedonic tone of an environmental odor is a powerful predictor of annoyance. Pertinent field surveys combined with laboratory analysis of landfill, pharmaceutical factories and rubber factories have been conducted, with the purpose of obtaining a behavior curve of the hedonic tone for specific odor emissions, and comparing the annoyance potential and odor persistence of the sources under investigation. The 9-point scale was used to determine the hedonic tone, and the odor concentration was measured using the Triangle Odor Bag Method. The concentration to be presented to panel members comprises a range of 5 or 6 dilution steps which differ by a factor of approximately 3. Using a suitable curve fitting procedure, a line can be fitted through the points obtained in the experiment. Characteristic H values at any concentration can be derived from the hedonic behavior curve. The relationship between the hedonic tone and lgOC conforms to the quadratic polynomial for the three sources. The persistence of odor is expressed as a dose (concentration) response and (intensity) function. According to the rate of change in odor intensity, the pharmaceutical odor is the strongest, followed by the landfill odor, and then the rubber odor. Annoyance potential is calculated by multiplying lgOC with the max hedonic value, meaning that the three sources are sorted as follows: rubber factory>landfill>pharmaceutical factory. This study will further the understanding of the sensory characteristics of different odor sources.

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Wpływ nanokrzemionki na mrozoodporność zapraw z cementu z dodatkiem popiołu lotnego, dojrzewających w warunkach korozyjnych, w różnych temperaturach

Zhang Yan, Liu Huaqing, Tong Ruiming, Ren Jun

Cement Wapno Beton

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2019

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R. 22/84, nr 2

137--153

PL

W Chinach buduje się dużą ilość wież betonowych na liniach do przesyłu bardzo wysokich napięć, z których wiele przecina zamarzające płaskowyże, a betonowy fundament wieży energetycznej narażony jest na zamarzanie i rozmrażanie, co zmniejsza jego wytrzymałość. W pracy badano zaprawy wykonane z cementu, popiołu lotnego i nanokrzemionki, które dojrzewały w roztworze siarczanów i chlorków przez 90 dni. Badano wytrzymałość, odporność na mróz, strukturę porów, strefę przejściową oraz wpływ dodatku nanokrzemionki na te właściwości. Wyniki badań pokazały, że dodatek nanokrzemionki poprawia odporność na mróz, a ten efekt można wyjaśnić poprawą struktury porów i zmniejszeniem porowatości strefy przejściowej z kruszywem. Przechowywanie betonu w roztworze agresywnym siarczanowo-chlorkowym ma niekorzystny wpływ na odporność na mróz, a powstawanie Aft, powodujące ekspansje może powodować powstawanie spękań betonu. Te wyniki uzasadniają ograniczenie wykonywania fundamentów betonowych wież do okresu letniego na zamarzających płaskowyżach, co zapewni ich lepsze właściwości.

EN

In China, a large amount of electric transmission towers has been built across plateau frozen soil, where the foundation concrete serves under freeze-thaw and erosion condition, and consequently, the durability faces the tough challenges. In this study, the mortars were prepared based on cement, fly ash, and nano silica [NS], which were cured in chloride-sulfate solution for 90 days. The compressive strength, freeze-thaw resistance, pore structure, interfacial transition zone, and hydration products was investigated, and the improvement in freeze-thaw resistance by addition of NS was discussed. The results show that addition of NS can improve the freeze-thaw resistance, and increase in curing temperature can also show improvement in freeze-thaw resistance. This effect can be explained by refine the pore structure and densify the microstructure of ITZ with the addition of NS. Furthermore, negative effect on freeze-thaw resistance can be found that being cured under chloride-sulfate condition, the formation of AFt would cause the volume expansion and cracking of concrete. Such results suggest that in the plateau frozen soil, it is better to cast concrete in summer, which would benefit the strength development of concrete and promote the freeze-thaw resistance.