In order to improve the teaching effect of mechanical design course, this paper discusses the teaching process from six aspects. It mainly includes the setting of basic courses, the revision of ...teaching plans and syllabus, the teaching of practical links, the experimental teaching of design courses, the integrated teaching process and the course design. It is the way to improve comprehensive quality of students. Through the combination of theory and practice, we pay attention to strengthening students’ ideological and political education and cultivating theirs innovative ability. Mechanical design plays a very important role in mechanical engineering technicians and mechanical industry. Therefore, it is of far-reaching significance to do a good job in the teaching of mechanical design.
•The three time monitoring parameters PDT, HDT, HLT are determined.•The characteristics of several common AE parameters are discussed.•Low frequency components dominate at the failure stage.•AE ...signals with high amplitude and high energy in the low-frequency can predict the failure.
Damage assessment of masonry buildings in service is the key to structural health monitoring. A uniaxial compression test of brick masonry specimens based on acoustic emission (AE) technology was conducted to monitor and assess the dynamic damage and failure mechanisms of masonry structures under load in real time. The variation characteristics of the ringing counts, energy, and peak frequency of the AE characteristic parameters of the masonry specimens during the entire uniaxial compression process were collected and recorded, and the reference values of the time parameters of AE monitoring were determined. Results showed that the number of AE ringing counts increased sharply and the slope of the cumulative energy curve increased remarkably at the final failure stage of the brick masonry specimens under compression. In addition, the component ratio of the peak frequency in the low-frequency band increased and that of the peak frequency in the high-frequency band decreased. The damage status of the masonry structures could be predicted qualitatively by the AE signals with high energy in the low-frequency band. The ringing counts of the AE sensors at different locations on the masonry specimens were compared, and the rationalities of the position and number of AE sensors fixed on the brick masonry specimens in the uniaxial compression test were discussed.
This letter presents a highly miniaturized continuously tunable microstrip line phase shifter from 10 to 67 GHz. The design takes the advantage of the microstrip line topology by a ground plane with ...defected ground structures (DGSs). This leads to slow wave (SW) effect of the transmission line (TL), thus the TL can be physically compact, while maintaining its electric length. By applying tunable microwave liquid crystal (LC) with an anisotropic permittivity as dielectric, a delay line phase shifter is realized. The proposed microstrip LC phase shifter with DGS and a standard microstrip LC phase shifter as reference are both filled with 20-mm-thick high-performance LC GT3-23001. By comparison, the one with DGS exhibits a significant SW effect and an improved LC tuning efficiency which leads to a remarkable enhancement of figure of merit (FoM) and compactness than the reference. A second microstrip LC phase shifter utilizing DGS filled with 5-mm thick more advanced GT7-29001 LC shows outstanding FoM of 55°/dB, compactness of <inline-formula> <tex-math notation="LaTeX">201^{\circ }/{\lambda }_{0} </tex-math></inline-formula>, and response time of 210 ms.
A convenient and straightforward method, which is based on catechol dyes and tyrosinase, for colorimetric determination and discrimination of dithiocarbamate pesticides (DTCs) has been fabricated. ...Three catechol dyes, including pyrocatechol violet (PV), pyrogallol red (PR), and bromopyrogallol red (BPR), were chosen as both substrates and indicators in this method. Tyrosinase can facilitate oxidation of the catechol dyes, altering color and absorbance spectra of the dyes. DTCs can alter the absorbance spectra of the catechol dyes–tyrosinase system due to their inhibitory effects on tyrosinase. As a result, the detection limit of the PV–tyrosinase system on ziram was determined to be 4.5 μg L–1. By implementing PV–tyrosinase, PR–tyrosinase, and BPR–tyrosinase, the colorimetric array successfully distinguished six DTCs (thiram, ziram, diram, ferbam, metiram, and mancozeb) at 5.0 μM using principal component analysis (PCA). The system can also determine ziram and distinguish DTCs in real samples. Furthermore, a smartphone can be used as a detector in this system to improve its real-world applications.
Identifying relatively weak areas is of great significance for improving the seismic reliability of structures. In this paper, a modal strain energy decomposition method is proposed, which can ...realize the decoupling of the comprehensive modal strain energy of a planar structure into three basic modal strain energies. According to the decomposition results, the modal strain energy decomposition diagram and the modal strain energy cloud diagram can be drawn so as to realize the quantitative and visual analysis of the vibration modes. The method is independent of load cases and can identify relatively weak areas of a structure from the perspective of inherent characteristics. The comparison with the shaking table test results of the two-story shear wall shows that the modal strain energy decomposition method can effectively identify the type of the relatively weak area of a structure and locate the position of the relatively weak area. Finally, the 6-story shear wall is analyzed by the modal strain energy decomposition method, and the relatively weak areas under the first two vibration modes are identified.
Drainage channels with step-pool configurations, one type of debris-flow drainage system used in gullies with steep gradients, have good application potential because of their high-performance ...control effect and engineering value. In this study, a pool depth design method is proposed based on the hydraulic jump theory. The dynamic behavior of debris flows in drainage channels with step-pool configurations is explored via a series of specially made flume experiments, where the debris-flow bulk density and the scale and depth of the step-pool configuration are the main controlling factors. The debris-flow pattern and flow depth are investigated along with the material-interchange phenomenon. There is a dramatic difference in the dynamic behaviors of different types of debris flows. Because of the associated intense turbulence and particle collision, the observed material-interchange phenomenon was greatest when the debris flow with a bulk density of 1700 kg/m
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passed through the drainage channel. The analysis indicated that, when a debris flow passes through a step-pool configuration, the flow depth increases significantly as a result of the hydraulic jump. However, a step-pool configuration with an overly large depth traps sediment, which is detrimental to transporting sediment. In addition, modified coefficients of the proposed design method were determined based on an analysis of the experimental results. The analysis further indicated that the coefficients significantly depend on the debris-flow viscosity and turbulence. Our results can be used to improve understanding of step-pool configurations and provide a reference for practical engineering design.
As a geriatric syndrome, sarcopenia has a high prevalence in the old population and represents an impaired state of health with adverse health outcomes. A strong clinical interest in its relationship ...with venous thromboembolism (VTE), which is a complex trait disease with a heterogeneous annual incidence rate in different countries, has emerged. The relationship between sarcopenia and venous thromboembolism has been reported in observational studies but the causality from sarcopenia to VTE remained unclarified. We aimed to assess the causal effect of sarcopenia on the risk of VTE with the two-sample Mendelian randomization (MR) method.
Two sets of single-nucleotide polymorphisms (SNPs), derived from two published genome-wide association study (GWAS) meta-analyses and genetically indexing muscle weakness and lean muscle mass separately, were pooled into inverse variance weighted (IVW), weighted median and MR-Egger analyses.
No evidence was found for the causal effect of genetically predicted muscle weakness (IVW: OR = 0.90, 95% CI = 0.76-1.06, p = 0.217), whole body lean mass (IVW: OR = 1.01, 95% CI = 0.87-1.17, p = 0.881) and appendicular lean mass (IVW: OR = 1.13, 95% CI = 0.82-1.57, p = 0.445) on the risk of VTE. However, both genetically predicted whole-body lean mass and appendicular lean mass can causally influence diabetes mellitus (IVW of whole-body lean mass: OR = 0.87, 95% CI = 0.78-0.96, p = 0.008; IVW of appendicular lean mass: OR = 0.71, 95% CI = 0.54-0.94, p = 0.014) and hypertension (IVW of whole-body lean mass: OR = 0.92, 95% CI = 0.87-0.98, p = 0.007; IVW of appendicular lean mass: OR = 0.84, 95% CI = 0.73-0.96, p = 0.013).
Genetically predicted sarcopenia does not causally influence VTE directly, but it might still have an indirect effect on VTE incidence via diabetes mellitus and hypertension.
Cardiac fibrosis is a pathological process of multiple cardiovascular diseases, which may lead to heart failure. Studies have shown that microRNAs (miRNAs) play critical roles in regulating mitophagy ...and cardiac fibrosis. We found that miR-24-3p expression was significantly downregulated in transverse aortic constriction (TAC) mice and cardiac fibroblasts (CFs) treated with Ang Ⅱ. We also found that, apart from improving cardiac structure and function, forced expression of miR-24-3p not only reduced the levels of collagen and α-SMA but also inhibited proliferation and migration of CFs. Next, our research proved that miR-24-3p suppressed the progression of mitophagy, autophagic flux, and the levels of mitophagy-related proteins in cardiac fibrosis models. Further analysis showed that PHB2 was a direct target of miR-24-3p. Finally, experiments showed that the knockdown of PHB2 reversed Ang Ⅱ-induced fibrosis in CFs. The results of our study suggests that increased expression of miR-24-3p contributes to the reduction of cardiac fibrosis and that it might be targeted therapeutically to alleviate cardiac fibrosis.
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Traditional plant disease diagnosis methods are mostly based on expert diagnosis, which easily leads to the backwardness of crop disease control and field management. In this paper, to improve the ...speed and accuracy of disease classification, a plant disease detection and classification method based on the optimized lightweight YOLOv5 model is proposed. We propose an IASM mechanism to improve the accuracy and efficiency of the model, to achieve model weight reduction through Ghostnet and WBF structure, and to combine BiFPN and fast normalization fusion for weighted feature fusion to speed up the learning efficiency of each feature layer. To verify the effect of the optimized model, we conducted a performance comparison test and ablation test between the optimized model and other mainstream models. The results show that the operation time and accuracy of the optimized model are 11.8% and 3.98% higher than the original model, respectively, while F1 score reaches 92.65%, which highlight statistical metrics better than the current mainstream models. Moreover, the classification accuracy rate on the self-made dataset reaches 92.57%, indicating the effectiveness of the plant disease classification model proposed in this paper, and the transfer learning ability of the model can be used to expand the application scope in the future.
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