21 research outputs found

    Novel Stability Analysis for Uncertain Neutral-Type Lur’e Systems with Time-Varying Delays Using New Inequality

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    This paper considers the delay-dependent stability analysis of neutral-type Lur’e systems with time-varying delays and sector bounded nonlinearities. First of all, using constructed function methods, a new Jensen-like inequality is introduced to obtain less conservative results. Second, a new class of Lyapunov-Krasovskii functional (LKF) is constructed according to the characteristic of the considered systems. Third, combining with the new inequality and reciprocal convex approach and some other inequality techniques, the new less conservative robust stability criteria are shown in the form of linear matrix inequalities (LMIs). Finally, three examples demonstrate the feasibility and the superiority of our methods

    Revealing the microstructures and seepage characteristics in the uncured rubber-cord composites using micro-computed tomography and lattice Boltzmann approach

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    The internal microstructure distribution of cord-rubber-air during the processing of uncured rubber-cord composites (URCs) determines the finished product's performance. For the first time, we used computed tomography (CT) and the lattice Boltzmann method (LBM) to establish a geometrical representation model of the real microscopic pore-fracture structures of URCs and investigate the seepage law of fluid in porous URCs, where the reinforced rubber formula was originally designed to reduce CT artifacts of cord. The results showed that the average porosity and pore radius of the original cord (0.2711 and 15.53 μm, respectively) were considerably larger than those of the URCs (0.0509 and 4.46 μm, respectively); the pore number of the cord was the largest when the pore radius was 5–10 μm, accounting for 29.36% of the total number; however, the pore number accounted for 31.36% of the total number of the URCs when the pore radius was 2–3 μm. Moreover, the characteristics of the pore/throat surface area and pore volume/throat length exhibited perfect consistent patterns with those of the pore radius. Furthermore, the fluid flow velocity increased in both cord and URCs as the displacement differential pressure increased, but decreased dramatically as the fluid kinematic viscosity increased. The critical values of displacement differential pressure and kinematic viscosity were different in the cord and URCs samples, presenting 11.1209 Pa/1.3696 × 10−3 m2/s and 14.2984 Pa/2.8869 × 10−4 m2/s, respectively. This phenomenon should be attributed that when the uncured rubber was injected into the original cord sample, its porosity decreased, its pore radius decreased, the number of micro-scale pores increased, and flow resistance became larger, resulting in a higher critical value of displacement differential pressure and a lower critical value of kinematic viscosity

    Improving the Electrochemical Performance of LiNi0.80Co0.15Al0.05O2 in Lithium Ion Batteries by LiAlO2 Surface Modification

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    LiNi0.80Co0.15Al0.05O2 (NCA) as a lithium ion battery cathode material has received attention for its highly specific capacity and excellent low temperature performance. However, the disadvantages of its high surface lithium compound residues and high pH value have influenced its processing performance and limited its application. This paper uses a facile method to modify NCA through LiAlO2 coating. The results showed that when the molar ratio of Al(NO3)3·9H2O and lithium compound residues at the surface of NCA cathode material was 0.25:1, the pH of the cathode material decreased from 12.70 to 11.80 and the surface lithium compound residues decreased from 3.99% to 1.48%. The NCA cell was charged and discharged for 100 cycles at 1 C in the voltage range of 3.0–4.3 V, to test the capacity retention of NCA. It was found to be as high as 94.67%, which was 5.36% higher than the control NCA cell. The discharge capacity of NCA-0.25-500 °C was 139.8 mAh/g even at 8 C rate, which was 15% higher than the raw NCA. Further research indicated that Al(NO3)3·9H2O reacted with the surface lithium compound residues of NCA and generated LiAlO2, which improved the NCA electrochemical performance

    Carbon Dioxide Retrieval from TanSat Observations and Validation with TCCON Measurements

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    In this study we present the retrieval of the column-averaged dry air mole fraction of carbon dioxide (XCO2) from the TanSat observations using the ACOS (Atmospheric CO2 Observations from Space) algorithm. The XCO2 product has been validated with collocated ground-based measurements from the Total Carbon Column Observing Network (TCCON) for 2 years of TanSat data from 2017 to 2018. Based on the correlation of the XCO2 error over land with goodness of fit in three spectral bands at 0.76, 1.61 and 2.06 μm, we applied an a posteriori bias correction to TanSat retrievals. For overpass averaged results, XCO2 retrievals show a standard deviation (SD) of ~2.45 ppm and a positive bias of ~0.27 ppm compared to collocated TCCON sites. The validation also shows a relatively higher positive bias and variance against TCCON over high-latitude regions. Three cases to evaluate TanSat target mode retrievals are investigated, including one field campaign at Dunhuang with measurements by a greenhouse gas analyzer deployed on an unmanned aerial vehicle and two cases with measurements by a ground-based Fourier-transform spectrometer in Beijing. The results show the retrievals of all footprints, except footprint-6, have relatively low bias (within ~2 ppm). In addition, the orbital XCO2 distributions over Australia and Northeast China between TanSat and the second Orbiting Carbon Observatory (OCO-2) on 20 April 2017 are compared. It shows that the mean XCO2 from TanSat is slightly lower than that of OCO-2 with an average difference of ~0.85 ppm. A reasonable agreement in XCO2 distribution is found over Australia and Northeast China between TanSat and OCO-2
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