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[en] Prediction models, based on ultimate analysis of biomass on dry basis (db) which is leveraged to predict chemical exergy, were proposed in this study. A new concept — chemical exergy per equivalent of available electrons transferred to oxygen (reductance degree) of model 1 was established. The result shows that chemical exergy per reductance degree of model 1 is relatively constant for the values of most biomass (db) beyond the±1% relative error range. A modified reductance degree of biomass was presented, whereas oxygen (O) content was neglected due to its inaccurate value and the high p-value for the coefficient of O variable. Chemical exergy per modified reductance degree of models 2 and 3 was approximated to be nearly a constant. Thus, two theoretical prediction models (model 2 and model 3) for the biomass (db) with and without sulfate (920.08(C/3 + H + S/8), 920.72(C/3 + H)) were established, respectively. The coefficients of the two models are of almost the same value, which indicates that the S content has also a negligible effect on chemical exergy. Model 3 (920.72(C/3 + H)) is also herein proposed for prediction of exergy of biomass. The average relative errors of model 1, model 2 and model 3 are 2.882%, 0.643% and 0.634%, respectively. - Highlights: • A new concept — chemical exergy per (modified) reductance degree is established. • Chemical exergy per modified reductance degree is approximately constant. • Estimation model of chemical exergy based on new concept provides higher accuracy. • Chemical exergy of biomass (db) can be easily estimated by simply using C and H.
[en] Highlights: • Solar cooker effect test of a telescope subreflector is conducted for the first time. • The cause and temperature distribution regularities are analyzed contrastively. • Simulation methods are proposed using light beam segmentation and tracking methods. • The validity of simulation methods is evaluated using the test results. - Abstract: The solar cooker effect can cause a local high temperature of the subreflector and can directly affect the working performance of the radio telescope. To study the daily temperature field and solar cooker effect of a subreflector, experimental studies are carried out with a 3-m-diameter radio telescope model for the first time. Initially, the solar temperature distribution rules, especially the solar cooker effect, are summarized according to the field test results under the most unfavorable conditions. Then, a numerical simulation for the solar temperature field of the subreflector is studied by light beam segmentation and tracking methods. Finally, the validity of the simulation methods is evaluated using the test results. The experimental studies prove that the solar cooker effect really exists and should not be overlooked. In addition, simulation methods for the subreflector temperature field proposed in this paper are effective. The research methods and conclusions can provide valuable references for thermal design, monitoring and control of similar high-precision radio telescopes.
[en] Highlights: • Solar non-uniform temperature field test of a telescope’s reflector is conducted initially. • Time-varying distribution regularities are analyzed contrastively. • Simulation methods are proposed involving environmental factors and self-shadowing. • Refined discrimination method for the shadow distribution is put forward. • Validity of simulation methods is evaluated with the experimental data. - Abstract: To improve the ability of deep-space exploration, many astronomers around the world are actively engaged in the construction of large-aperture and high-precision radio telescopes. The temperature effect is one of three main factors affecting the reflector accuracy of radio telescopes. To study the daily non-uniform temperature field of the main reflector, experimental studies are first carried out with a 3-m-aperture radio telescope model. According to the test results for 16 working conditions, the distribution rule and time-varying regularity of the daily temperature field are summarized initially. Next, theoretical methods for the temperature field of the main reflector are studied considering multiple environmental parameters and self-shadows. Finally, the validity of the theoretical methods is evaluated with test results. The experimental study demonstrates that the non-uniform temperature distribution of the main reflector truly exists and should not be overlooked, and that the theoretical methods for the reflector temperature field proposed in this paper are effective. The research methods and conclusions can provide valuable references for thermal design, monitoring and control of similar high-precision radio telescopes.
[en] Sharp and non-uniform temperature changes of steel members due to solar radiation may cause potential security problems in large-span spatial steel structures. To determine the rules governing thermal stress and deformation of steel members under solar radiation and to obtain the relationship between temperature and thermal stress, experiments were designed and conducted with common steel members including rectangular steel tube, steel I-beam, and circular steel tube, under different constraints. Using the test data, the solar-induced temperature effects on each, especially bending stress, are analyzed in detail. Moreover, a numerical method to simulate the effect of temperature changes on steel members is evaluated against measured results to assess its validity. The experimental study demonstrates that the effect of temperature on steel members is significant and cannot be overlooked and that the numerical simulation presented in this paper is effective. The test procedure and research conclusions provide significant resources for thermal design, monitoring, and control of large-span spatial steel structures.
[en] Highlights: • Mechanical behavior of containment during prestressing construction is studied. • A refined model of a prestressed concrete containment is established. • Accuracy of simulation method is verified by comparing with measured data on site. • A reasonable optimization scheme for prestressing construction is proposed. - Abstract: Taking a third generation nuclear power plant as the research background, a refined model of a prestressed concrete containment which consisted of 270 complex spatial prestressed tendons was accurately established, using FE software ABAQUS. The cooling method was adopted to simulate the tensioning process of tendons. The simulation method of the tensioning of tendons during the prestressing construction of containment was verified by comparing with the measured data on site of the practical project. The mechanical behavior of the containment during the prestressing construction according to the prestressing construction scheme on site was studied in detail. Then the influence of steel liner and reinforcement on mechanical behavior of the containment during the prestressing construction of prestressed tendons was discussed. Finally, four prestressing construction schemes were analyzed and a reasonable optimization scheme was obtained.