Multi-material Topology Optimization Based on Multiple SIMP of Variable Density Method

In this paper a multiple SIMP (solid isotropic material with penalization model) of variable density method is proposed to solve the problem of muli-material topology optimization. All candidate materials including void material are arranged in descending order of elastic modulus. The material conversion scheme of multiple SIMP is based on the elastic modulus of the candidate material after interpolation. Based on the guide-weight method, the iterative criterion of muti-material topology optimization is derived from the Kuhn-Tucker condition. Three examples show that the proposed method is effective and robust to solve the problem of muti-material topology optimization.

An optical regenerative wavelength conversion scheme for satellite based on SPM of SOA and offset filter

An optical regenerative wavelength conversion scheme without separated pump laser is put forward to promote the wavelength utilization ratio in distributed satellite network. The scheme adopts the self-phase modulation(SPM) in semiconductor optical amplifier(SOA) to broaden the signal spectrum toward both higher and lower frequency owing to the property that the time of carrier recover is less than pulsewidth. Then the signal light and pump light are extracted by a high-pass filter and a low-pass filter respectively. Finally, the wavelength conversion is realized based on the four-wave mixing(FWM), where the signal light and pump light are passing through another SOA. The simulation results demonstrate that the conversion efficiency can be more than 15dB, and the Q factor improvement can reach to 4dB when input power is small than -22dBm.

Calibration of High-Impact Short-Range Quantitative Precipitation Forecast through Frequency-Matching Techniques

Short-lived and intense rainfall is common in Hong Kong during the wet season and often causes disruption to daily lives. As global numerical weather prediction (NWP) models are progressively improved, representation of sub-synoptic or mesoscale systems associated with intense rainfall is better parametrized and resolved than ever before, but their quantitative precipitation forecasts (QPFs) still tend to underestimate the magnitude of intense rainfall. This study calibrated model QPFs over the region of Hong Kong by two frequency-matching methods. In both methods, conversion schemes between the direct model output (DMO) and calibrated forecasts were first established by matching the cumulative distribution to that of the observed data. The “Adaptive Table” method updated the conversion scheme whenever the latest observation fell out of its expected range in the existing scheme, whereas the “Sliding Window” method reconstructed the conversion scheme using data from the most recent two years. The calibration methods had been verified against actual rainfall events with different thresholds, and it was found that both methods could improve model performance for moderate and heavy rainfall in short-range forecasts with similar effectiveness. They were also able to reduce the systematic bias of precipitation forecasts for significant rainfall throughout the verification period.

Kinetic scheme of apple pectin oxidative transformations under the action of the ozone-oxygen mixture

Mathematical modeling of apple pectin oxidative transformations (AP) under the action of the ozone-oxygen mixture in aqueous solutions (the reaction system "AP + O3 + O2 + H2O") has been carried out. The kinetic scheme of the oxidation process was compiled basing on the well-known ideas of liquid-phase oxidation mechanisms of organic compounds (taking into account the currently known experimental results on AP oxidation). Using the "KhimKinOptima" software package for the proposed scheme, the inverse and direct chemical kinetics problems were solved. The well-known literature data on the rate constants of elementary stages were used. The rate constants of the oxidation key stages have been determined after solving the chemical kinetics inverse problem with the index method of the observed and calculated kinetic data global optimization. It turned out that the rate constants of the individual stages obtained by calculation are in good agreement with the values of the rate constants taken from literary sources. The chemical kinetics direct problem has been solved with the found rate constants and allowed obtaining kinetic curves of all participants in the apple pectin ozonized oxidation. It was found that the kinetic curve of the accumulation of carboxyl groups, obtained experimentally, completely coincided with the theoretical dependence. It has been also shown that the proposed apple pectin oxidative conversion scheme in the "AP + O3 + O2 + H2O" reaction system allows one to explain all the currently available experimental results. The apple pectin ozonized oxidation under another initiator (Н2О2 + FeSO4) has been studied to confirm the kinetic scheme. To do this, 3 new stages has been introduced into the scheme proposed, characterizing the catalytic decomposition of hydrogen peroxide under a transition metal (Fe2+). By solving the chemical kinetics direct problem, the accumulation kinetic curves of the final reaction products were obtained. It has been found that the carboxyl groups accumulation kinetics in the reaction system "AP + O3 + O2 + H2O2 + FeSO4 + H2O" after the supplementary experiment coincided with the theoretical kinetic curve. Thereby, the accuracy of the apple pectin proposed oxidative conversion scheme is confirmed.