Stability on the Excavation Surface of Submarine Shield Tunnel Considering the Fluid–Solid Coupling Effect and the Equivalent Layer

The support pressure on an excavation surface is a critical factor in the ground deformation and excavation stability of a submarine shield tunnel. The shield tail gap and the disturbance zone of grouting behind the tunnel wall are also important influencing factors. However, the effects of these factors on excavation stability are difficult to quantify. Consequently, a homogeneous, elastic, and annular equivalent layer is employed to simulate the thin layer behind the tunnel wall. Using COMSOL Multiphysics software, the effects of the water level depth, the thickness of the equivalent layer, the diameter of the shield tunnel, and the internal friction of soil and tunnel burial depth on the excavation deformation and ground surface subsidence of a submarine tunnel are considered with regard to the fluid–solid coupling effect. The result show that the surface subsidence of the case with respect to the fluid–solid coupling effect and the equivalent layer is larger than that without interstitial fluid and the equivalent layer, indicating that the present model can better simulate the stability of tunnel excavation. Therefore, it is important to consider the impact of the fluid–solid coupling effect and the equivalent layer on the deformation of the excavation face and ground surface subsidence

Characterization of the Major Odor-Active Compounds in Dry Jujube Cultivars by Application of Gas Chromatography–Olfactometry and Odor Activity Value

The volatile compounds of jujube (Ziziphus jujube Mill.) puree obtained from three cultivars, ‘Jinsixiaozao’ (Y1), ‘Youzao’ (Y2), and ‘Yuzao’ (Y3), were analyzed by gas chromatography–olfactometry (GC–O), gas chromatography–mass spectrometry, gas chromatography–flame photometric detection, and a nitrogen phosphorus detector. The results showed that a total of 37, 37, and 35 odor-active compounds were identified by GC–O in samples of Y1, Y2, and Y3, respectively. In addition, the odor activity value (OAV) was used to determine the important compounds. The results demonstrated that hexanal (OAV of 39–85), (<i>E</i>)-2-octenal (OAV of 32–70), β-damascenone (OAV of 14–49), ethyl hexanoate (OAV of 22–39), 3-mercaptohexyl acetate (OAV of 17–24), and 2,5-dimethylpyrazine (OAV of 17–22) were key odor-active compounds. It is of great significance to develop high-grade jujube food by determining key odor-active compounds. Furthermore, four volatiles (hexanal, 1-octen-3-ol, 3-mercapohexyl acetate, and benzaldehyde) reduced the overall threshold value by 2.36, 1.01, 1.34, and 1.19, respectively

Preparation of micro-encapsulated strawberry fragrance and its application in the aromatic wallpaper

Micro-encapsulated strawberry fragrance was successfully prepared with wall materials including maltodextrin, sodium octenylsuccinate and gum Arabic. The micro-capsule was added to wallpaper and aromatic wallpaper with strawberry characteristics was obtained. The particle distribution, surface morphology, chemical structure, thermal property and controlled release performance of micro-encapsulated fragrance and aromatic wallpaper were investigated using laser particle size analyzer, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-TR), thermal gravity analysis (TGA) and chromatography-mass spectrometer (GC-MS). The results showed that the average diameter of micro-capsule was 2 μm and the particles mainly distributed in the tissues of wallpaper. The result of TGA showed that the micro-capsule had a good stability. Meanwhile, the aromatic wallpaper had strawberry aroma more than 3 months and took on excellent controlled release performance

Characterization of aroma-impact compounds in dry jujubes (Ziziphus jujube Mill.) by aroma extract dilution analysis (AEDA) and gas chromatography-mass spectrometer (GC-MS)

Aroma-impact compounds of dry jujubes obtained from Z. jujuba Mill. cv. “tangzao” (Y1), Z. jujuba Mill. cv. “muzao” (Y2), Z. jujuba Mill. cv. “lizao” (Y3), and Z. jujuba Mill. cv. “qingrunhongzao” (Y4) were analyzed by gas chromatography-olfactometry (GC-O). The result revealed 35, 29, 34, and 33 aroma-impact volatiles in the Y1, Y2, Y3, and Y4 samples, respectively. The compounds bearing the highest FD factor in each sample were (E)-2-hexenal, (E)-2-heptenal (FD = 256) for Y1, 2,3-butanedione, (E)-2-hexenal, 2,5-dimethylpyrazine, (E)-2-heptenal and β-damascenone (FD = 64) for Y2, 2,3-butanedione and β-damascenone (FD = 256) for Y3, and 2,5-dimethylpyrazine (FD = 256) for Y4

A Novel Strength Model for Cement Marine Clay Based on the Mechanical-Chemical Coupling Behavior

Crucial mechanical-chemical (MC) interactions occur during the cement hydration process in cement marine clay; however, the role of such an important element of the resulting strength has been subject to less investigation, particularly from the theoretical perspective. To overcome this scientific gap, an efficient strength-based model accounting for the coupled MC processes is proposed here. Based on the analysis of the cement hydration mechanism, the porosity was chosen as the main factor to characterize the influence of the MC interactions on the overall response. To verify the accuracy of the MC model, the unconfined compressive strength (UCS) experiment was conducted for the cement marine clay samples, and the corresponding simulation model was constructed using COMSOL multiphysics®. In addition, a comparison between the predicted results by the existing three strength models and the proposed MC model was performed. Subsequently, the sensitivity analysis and identification of mechanical parameters were carefully carried out. The obtained results show that the UCS strength for Taizhou clay ranges from 10.21 kPa to 354.2 kPa as the cement content increases from 10% to 20%, and the curing time varies from 3 days to 28 days. The mechanical parameters in the MC model can be obtained according to the porosity level. A reasonably good agreement between the UCS strength results of simulations and the experimentally observed data is reported. Additionally, the predicted UCS strength results by the MC model demonstrate the best correspondence with the measured values, indicating the high efficacy of the established model

Characterization of the Key Aroma Compounds of Three Kinds of Chinese Representative Black Tea and Elucidation of the Perceptual Interactions of Methyl Salicylate and Floral Odorants

Jinjunmei (JJM), Keemun (KM), and Dianhong (DH) are the representative black teas in China, and they have always been favored by consumers. In this study, we aim to obtain the aroma characteristic information of volatile components in black tea samples through headspace solid-phase microextraction (HS-SPME), solvent-assisted flavor evaporation (SAFE), and gas chromatography-mass spectrometry combined with gas chromatography-olfactometry technology. The results showed that 70 compounds including &alpha;-methylbenzyl alcohol (isomer of &beta;-phenylethanol) were identified as odorants. Among them, 39 compounds such as linalool and geraniol showed a high degree of aroma contribution. Furthermore, the Feller&rsquo;s additive model was used to explore the perceptual interactions among the methyl salicylate and the floral compounds (10 groups): five groups of binary compounds showed masking effect after mixing, one group showed additive effect, and four groups showed synergistic effect. The ratio (R) was compared with the aroma index (n) of Steven&rsquo;s law, which found a high-fitness exponential relationship. The results of this study help to provide additional and new theoretical guidance for improving the aroma quality of black tea