Accelerating sensitivity analysis in structural topology optimization using deep neural network

In recent years, Topology Optimization (TO) has been increasingly gaining attention with the development of new constructing techniques. In the optimization process of a density-based TO method, the sensitivities of the design variables are often computed using numerical methods like Finite Element Method (FEM). Such operation is performed repetitively for tens or hundreds of iteration steps, therefore generating huge computational cost for large scale design scenarios. This paper proposes to accelerate TO by replacing the full-scale sensitivity analysis of FEM with a reduced-scale case, and adopting a deep neural network to map the reduced-scale sensitivity field back to fine scale. Three neural network models are trained and tested using training data generated by structures of three difference scales. The results show that the proposed network successfully reduced the time cost to a large extent, while preserving the topology of the optimized design

Surface Transformations and Water Uptake on Liquid and Solid Butanol near the Melting Temperature

Water interactions with organic surfaces are of central importance in biological systems and many Earth system processes. Here we describe experimental studies of water collisions and uptake kinetics on liquid and solid butanol from 160 to 200 K. Hyperthermal D2O molecules (0.32 eV) undergo efficient trapping on both solid and liquid butanol, and only a minor fraction scatters inelastically after an 80% loss of kinetic energy to surface modes. Trapped molecules either desorb within a few ms, or are taken up by the butanol phase during longer times. The water uptake and surface residence time increase with temperature above 180 K indicating melting of the butanol surface 4.5 K below the bulk melting temperature. Water uptake changes gradually across the melting point and trapped molecules are rapidly lost by diffusion into the liquid above 190 K. This indicates that liquid butanol maintains a surface phase with limited water permeability up to 5.5 K above the melting point. These surface observations are indicative of an incremental change from solid to liquid butanol over a range of 10 K straddling the bulk melting temperature, in contrast to the behavior of bulk butanol and previously studied materials.Comment: 28 pages, 4 figures + introduction figur

Alkali interactions with a calcium manganite oxygen carrier used in chemical looping combustion

Chemical-Looping Combustion (CLC) of biofuels is a promising technology for cost-efficient CO2 separation and can lead to negative CO2 emissions when combined with carbon capture and storage. A potential challenge in developing CLC technology is the effects of alkali metal-containing compounds released during fuel conversion. This study investigates the interactions between alkali and an oxygen carrier (OC), CaMn0.775Ti0.125Mg0.1O3-δ, to better understand the fate of alkali in CLC. A laboratory-scale fluidized bed reactor is operated at 800–900 \ub0C in oxidizing, reducing and inert atmospheres to mimic CLC conditions. Alkali is fed to the reactor as aerosol KCl particles, and alkali in the exhaust is measured online with a surface ionization detector. The alkali concentration changes with gas environment, temperature, and alkali loading, and the concentration profile has excellent reproducibility over repeated redox cycles. Alkali-OC interactions are dominated by alkali uptake under most conditions, except for a release during OC reduction. Uptake is significant during stable reducing conditions, and is limited under oxidizing conditions. The total uptake during a redox cycle is favored by a high alkali loading, while the influence of temperature is weak. The implications for the understanding of alkali behavior in CLC and further development are discussed

Alkali-wall interactions in a laboratory-scale reactor for chemical looping combustion studies

Alkali metal-containing compounds are readily released during thermal conversion of solid fuels, and may have both detrimental and beneficial effects on chemical looping combustion. Here, we characterize alkali interactions with the inner walls of a laboratory-scale reactor under oxidizing, reducing and inert conditions at temperatures up to 900 \ub0C. KCl aerosol particles are continuously introduced to the stainless steel reactor and the alkali concentration is measured on-line with a surface ionization detector. Aerosol particles evaporate at temperatures above 500 \ub0C and KCl molecules rapidly diffuse to the reactor wall. Up to 92% of the alkali reaching the wall below 700 \ub0C remains adsorbed, while re-evaporation is important at higher temperatures, where up to 74% remains adsorbed. Transient changes in alkali concentration are observed during repeated redox cycles, which are associated with changes in chemical composition of the wall material. Metal oxides on the reactor wall are partially depleted under reducing conditions, which allow for the formation of a new potassium-rich phase that is stable in a reducing atmosphere, but not under inert conditions. The observed wall effects are concluded to be extensive and include major transient effects depending on gas composition, and the implications for laboratory studies and improved experimental methodology are discussed

Changes in CCN activity of ship exhaust particles induced by fuel sulfur content reduction and wet scrubbing

Maritime transport remains a large source of airborne pollutants, including exhaust particles that can act as cloud condensation nuclei (CCN). While primary diesel engine exhaust particles are generally considered hydrophobic, international regulations targeting a reduction of particulate emissions from ships may have secondary effects, and therefore influence how exhaust interacts within the atmosphere. The effect of international fuel sulfur content (FSC) regulations on the cloud forming abilities of exhaust particles was investigated using a marine test engine operating on compliant low FSC fuels, non-compliant high FSC distillate fuels and in conjunction with a marine wet scrubber (fresh- and seawater). Particle sizing and liquid droplet activation measurements reveal that compliance measures can have opposing effects on the CCN activity of exhaust particles. For a non-compliant, high FSC fuel, wet scrubbing leads to an increase in CCN activity but not to significant increases in CCN emission factors. However, switching to low FSC fuels resulted in emissions of highly hydrophobic particles, causing a significant reduction in CCN activity resulting in smaller CCN emission factors by at least one order of magnitude. Our observations are supported by chemical analysis of exhaust particles using scanning transmission X-ray microscopy and near edge X-ray absorption fine structure (STXM/NEXAFS) spectra. Potential implications of effects on ship exhaust particles for cloud and climate interactions due to different compliance measures are discussed

Research on thermal infrared anomaly characteristics of moderate strong earthquakes in northeast China

In this article, the daily brightness temperature data from January 2006 to May 2020 of China’s geostationary meteorological satellite FY-2E/G were used to identify the brightness temperature differences before deep and shallow earthquakes in the study area using wavelet transform and the relative wavelet power spectrum (RWPS) methods. The objective was to explore the characteristics of thermal infrared (TIR) radiation anomaly changes before deep and shallow earthquakes in Northeast China by carrying out anomaly extraction and data analysis. The research has shown that five significant earthquakes experienced TIR radiation anomalies in the vicinity of the epicenter approximately 1–2 months before the event. The amplitude of the anomaly ranged from seven to twenty times higher than average, and the anomaly lasted about 3 months. The infrared radiation anomaly characteristics before the earthquake were especially significant in the case of two earthquakes in the Songyuan area. From the research, it was concluded that the TIR radiation anomaly could act as a short-term precursor for earthquake prediction. The method employed in this study would provide great support for predicting deep and shallow earthquakes in Northeast China using satellite thermal infrared technology

Analysis of Metabolites Difference of the Albino Tea Tree Variety 'Ming Guan'

‘Ming guan’ is a new excellent albino tea variety bred from the descendants of Bai jiguan. In order to explore the quality difference of Ming guan multi tea processing, the fresh leaves of Ming guan were used as raw materials to make the corresponding tea types according to the processing methods of green tea, black tea and white tea, and sensory quality evaluation, aroma and taste analysis were conducted. The results showed that the aroma of Ming guan green tea was tender, floral and fruity, with a mellow taste, the aroma of Ming guan black tea was sweet, floral, with a sweet taste, the aroma of Ming guan white tea was millets, floral, with a fresh taste, and the different processes of Ming guan tea had their own unique floral characteristics. Among the aroma components of Ming guan green tea, terpene aroma components with floral aroma were relatively more abundant, followed by ester aroma components with fruit aroma, which played an important role in the formation of the aroma of Ming guan green tea. The representative aroma components of Ming guan green tea were leaf alcohol ester of foliol caproate, 3-hexenyl caproate, 2-hexenyl caproate, nerolidol, leaf alcohol ester of butyric acid, olivetol and α-farnesene, the representative components of which were mainly esters with fruity aroma and alcohols with floral and fruity aroma, creating the characteristic of Ming guan green tea floral and fruity varieties. The representative components of Ming guan black tea were dihydrolinalool, α-cephalene, β-Ionone, γ-cadinene, methyl hexadecanoic acid and benzaldehyde, which were mainly terpenes and alcohols with floral and sweet aromas, contributing to the floral and sweet aromatic characteristics of Ming guan black tea. The representative components of Ming guan white tea were geraniol, myrcene, 3-carene, linalyl acetate and linalool, and the representative components are mainly alcohols and terpenes with floral aroma. The non-volatile components of Ming guan green tea, Ming guan black tea and Ming guan white tea vary greatly overall. The content of catechins, anthocyanins, some flavonols and flavonoid glycosides (quercetin-3-O-galactoside, quercetin-3-O-glucoside, quercetin-3-O-glucoside 7-O-rhamnoside, etc.) in Ming guan green tea was generally higher than that in Ming guan black tea and Ming guan white tea. The contents of theaflavins, phenolic acids, a few flavonol and flavonoid glycoside compounds (vitexin-2-O-galactoside, vitexin-2-O-rhamnoside, apigenin-6,8-di-C-glucoside, apigenin-6-C-glucoside, etc.) and some amino acid compounds (L-phenylalanine, L-tryptophan, L-isoleucine, L-valine, L-aspartic acid) in Ming guan black tea were higher than those in Ming guan green tea and Ming guan white tea.The content of some amino acid compounds (L-arginine, L-glutamine, L-lysine, L-histidine, L-tyrosine) in Ming guan white tea was higher than that in Ming guan green tea and Ming guan black tea, which may be affected by different processing technologies. This study could provide a theoretical basis for a comprehensive understanding of the chemical basis and quality differences of Ming guan green tea, Ming guan black tea and Ming guan white tea

Collision Dynamics and Solvation of Water Molecules in a Liquid Methanol Film

Environmental molecular beam experiments are used to examine water interactions with liquid methanol films at temperatures from 170 K to 190 K. We find that water molecules with 0.32 eV incident kinetic energy are efficiently trapped by the liquid methanol. The scattering process is characterized by an efficient loss of energy to surface modes with a minor component of the incident beam that is inelastically scattered. Thermal desorption of water molecules has a well characterized Arrhenius form with an activation energy of 0.47{\pm}0.11 eV and pre-exponential factor of 4.6 {\times} 10^(15{\pm}3) s^(-1). We also observe a temperature dependent incorporation of incident water into the methanol layer. The implication for fundamental studies and environmental applications is that even an alcohol as simple as methanol can exhibit complex and temperature dependent surfactant behavior.Comment: 8 pages, 5 figure