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This paper takes the frame as the research object and explores the vibration characteristics of the frame to address the vibration problem of a 1-MSD straw-crushing and residual film recycling machine in the field operation process, and an accurate identification of the modal parameters of the frame is carried out to solve the resonance problem of the machine, which can achieve cost reduction and increase income to a certain extent. The first six natural frequencies of the frame are extracted by finite element modal identification and modal tests, respectively. The rationality of the modal test results is verified using the comprehensive modal and frequency response confidences. The maximum frequency error of modal frequency results of the two methods is only 6.61%, which provides a theoretical basis for the optimal design of the frame. In order to further analyze the resonance problem of the machine, the external excitation frequency of the machine during normal operation in the field is solved and compared with the first six natural frequencies of the frame. The results show that the first natural frequency of the frame (18.89 Hz) is close to the external excitation generated by the stripping roller (16.67 Hz). The first natural frequency and the volume of the frame are set as the optimization objectives, and the optimal optimization scheme is obtained by using the Optistruct solver, sensitivity method, and grey correlation method. The results indicate the first-order natural frequency of the optimized frame is 21.89 Hz, an increase of 15.882%, which is much higher than the excitation frequency of 16.67 Hz, and resonance can be avoided. The corresponding frame volume is 9.975 × 107 mm3, and the volume reduction is 3.46%; the optimized frame has good dynamic performance, which avoids the resonance of the machine and conforms to the lightweight design criteria of agricultural machinery structures. The research results can provide some theoretical reference for this kind of machine in solving the resonance problem and carrying out related vibration characteristics research. [ABSTRACT FROM AUTHOR]

A rice classification method for the fast and non-destructive differentiation of different varieties is significant in research at present. In this study, fluorescence hyperspectral technology combined with machine learning techniques was used to distinguish five rice varieties by analyzing the fluorescence hyperspectral features of Thai jasmine rice and four rice varieties with a similar appearance to Thai jasmine rice in the wavelength range of 475–1000 nm. The fluorescence hyperspectral data were preprocessed by a first-order derivative (FD) to reduce the background and baseline drift effects of the rice samples. Then, a principal component analysis (PCA) and t-distributed stochastic neighborhood embedding (t-SNE) were used for feature reduction and 3D visualization display. A partial least squares discriminant analysis (PLS-DA), BP neural network (BP), and random forest (RF) were used to build the rice classification models. The RF classification model parameters were optimized using the gray wolf algorithm (GWO). The results show that FD-t-SNE-GWO-RF is the best model for rice classification, with accuracy values of 99.8% and 95.3% for the training and test sets, respectively. The fluorescence hyperspectral technique combined with machine learning is feasible for classifying rice varieties. [ABSTRACT FROM AUTHOR]

Nanomaterials have been widely used for improving the physicochemical properties of geomaterials. However, quantitative interpretation of the microscopic mechanisms is still not well understood. In this study, a statistical principle was applied to study the microscopic characteristics of nano-silica (NS) modified silty clay. We use mercury intrusion porosimetry (MIP) to measure the micro-pore parameters (median pore diameter and cumulative volume of pore diameters smaller than 0.1 µm) based on various NS-modified silty clays (NS mass contents 0, 0.25%, 1%, and 3%). The test results indicate two micro-pore parameters have significant randomness and uncertainty, and soil pores become smaller and more compacted. Furthermore, four potential probability distributions were selected to compare with measured data. All distributions agree excellently with the experimental data, and three distributions satisfy the hypothesis testing, except the Weibull distribution. Finally, according to the information spread estimation method and chi-square test effect evaluation indexes, the normal distribution was proposed because it has the optimal described effect for the statistical characteristics of NS-modified silty clay. These results have important implications for understanding the randomness and evolution of microstructures of NS geomaterials, which are helpful to guide the evaluation of freezing process and water transport in modified soils. [ABSTRACT FROM AUTHOR]

The Middle-Upper Cambrian Xixiangchi Formation in the Sichuan Basin is regarded as an important reservoir with great potential for hydrocarbon exploration. It is previously indicated that the Xixiangchi carbonates have experienced extensive dolomitization, however, the origin of dolomitizing fluids and the dolomitization mechanism still remain uncertain. In this study, a set of petrographic and geochemical examinations, including rare earth elements (REE) and isotopic (C, O, and Sr) compositions were used to trace the origins of dolomitizing fluids and associated diagenetic processes. The petrographic examination revealed three types of matrix dolomites (D1, D2, D3) and one cement saddle dolomite (SD). These phases have crystal size ranges of less than 30 μm (very fine to fine crystals, D1), 30–100 μm (fine to medium crystals, D2), 100–300 μm (medium to coarsely crystalline dolomite, D3), and 0.3–4 mm (fracture filling cements, SD), respectively. D1 is characterized by non to very weak luminescence, weakly negative Ce anomalies (Ce/Ce* = 0.84 ± 0.02), strongly negative Eu anomalies (Eu/Eu* = 0.65 ± 0.03), and high 87Sr/86Sr ratios (0.71062 ± 0.00122). In combination with δ13C (−1.5‰ ± 0.2‰) and δ18O (−9.7‰ ± 0.5‰) compositions, D1 is interpreted to be formed by penecontemporaneous dolomitization in the near-surface environment with seawater as the dolomitizing fluid. In contrast, D2 is characterized by intercrystalline pores, dirty crystal surfaces, similar δ13C (−1.4‰ ± 0.4‰) compositions but higher δ18O (−8.9‰ ± 0.7‰) compositions, and lower 87Sr/86Sr ratios (0.70992 ± 0.00035), similar Ce anomalies (Ce/Ce* = 0.87 ± 0.04) and higher Eu anomalies (Eu/Eu* = 0.85 ± 0.04). The coarser D2 is regarded to be formed by the post-penecontemporaneous seepage-reflux dolomitization or by recrystallization of D1 dolomite in a near-surface or shallow burial environment. D3 is distinguished by a cloudy core with clear rims, showing slightly higher Eu anomalies (Eu/Eu* = 0.88 ± 0.02) and similar Ce anomalies (Ce/Ce* = 0.88 ± 0.02) than those of D1 and D2. Combined with the δ18O compositions (−10.4‰ ± 0.4‰) and 87Sr/86Sr ratios (0.70989 ± 0.00048), D3 is thought to be formed by the overgrowth or recrystallization of D1 and D2 dolomites in a shallow to moderate burial environment. The fractures filling SD dolomite consists of nonplanar and much coarser crystals with undulatory extinctions and brighter red luminescence. The lower δ18O (−11.1‰ ± 0.3‰) compositions, lower negative Eu anomalies (Eu/Eu* = 0.70 ± 0.01) of SD than the matrix dolomites, and similar Ce anomalies (Ce/Ce* = 0.83 ± 0.01) are indicative of hydrothermal dolomitization, with possible fluids associated with the magma during the period of Emei taphrogenic movement. In addition, the 87Sr/86Sr ratios (0.70941 ± 0.00003) of SD suggest probable origin from the coeval seawater partially. Therefore, SD dolomite is interpreted to be formed by hydrothermal dolomitization with mixed dolomitizing fluid of seawater and hydrothermal fluids. In summary, all the matrix dolomites have almost the same ΣREE concentrations and exhibit similar near-flat REE partition patterns with weak LREE enrichments, weakly negative Ce anomalies, and negative Eu anomalies. Such characteristics of REE compositions are indicative of similar evolved dolomitizing fluid, such as seawater or seawater- derived fluids. By contrast, SD dolomites have a different REE partition pattern with left-leaning characteristics, LREE depletions, and negative Eu anomalies, thus suggesting a different dolomitizing fluid source from the matrix dolomites. In addition, the development of intercrystalline pores associated with D2 dolomite makes it more likely to be a potential reservoir, indicating that the dolomitizing history of carbonate has a strong influence on the quality of potential dolomite reservoirs. [ABSTRACT FROM AUTHOR]

The production of goat meat is determined by the growth speed of muscle fibers, and the autophagy and apoptosis of myoblast cells is a crucial process in the growth of muscle fibers. The rapid growth of muscle fibers occurs from one month old to nine months old in goats; however, the mechanisms of myoblast cells' autophagy and apoptosis in this process are still unknown. To identify candidate genes and signaling pathway mechanisms involved in myoblast apoptosis and autophagy, we compared the expression characteristics of longissimus dorsi tissues from Wu'an goats—a native goat breed of China—at 1 month old (mon1 group) and 9 months old (mon9 group). Herein, a total of 182 differentially expressed mRNAs (DEGs) in the mon1 vs. mon9 comparison, along with the KEGG enrichments, showed that the PI3K-Akt pathway associated with autophagy and apoptosis was significantly enriched. Among these DEGs, expression of vacuole membrane protein 1 (VMP1)—a key gene for the PI3K-Akt pathway—was significantly upregulated in the older goats relative to the 1-month-old goats. We demonstrated that VMP1 promotes the proliferation and autophagy of myoblasts, and inhibits their apoptosis. The integration analysis of miRNA–mRNA showed that miR-124a was a regulator of VMP1 in muscle tissue, and overexpression and inhibition of miR-124a suppressed the proliferation and autophagy of myoblasts. The PI3K/Akt/mTOR pathway was an important pathway for cell autophagy. Additionally, the activator of the PI3K/Akt/mTOR pathway, the expression of VMP1, and ULK1 were higher than the negative control, and the expression of mTOR was depressed. The expression of VMP1, ULK1, and mTOR was the opposite when the inhibitor was added to the myoblasts. These results show that the PI3K/Akt/mTOR pathway promoted the expression of VMP1 and ULK1. By using adenovirus-mediated apoptosis and proliferation assays, we found that that miR-124a inhibits myoblast proliferation and autophagy, and promotes their apoptosis by targeting VMP1. In conclusion, our results indicated that VMP1 was highly expressed in the LD muscle tissues of nine-month-old goats, and that it was regulated by miR-124a to inhibit myoblast cells' apoptosis through the PI3K/Akt/mTOR pathway, and to promote proliferation and autophagy. These findings contribute to the understanding of the molecular mechanisms involved in myoblast proliferation, autophagy, and apoptosis. [ABSTRACT FROM AUTHOR]