Research on the design method for uniform wear of shield cutters in sand-pebble strata

During shield tunneling in highly abrasive formations such as sand–pebble strata,nonuniform wear of shield cutters is inevitable due to the different cutting distances.Frequent downtimes and cutter replacements have become major obstacles to long-distance shield driving in sand–pebble strata.Based on the cutter wear characteristics in sand–pebble strata in Beijing,a design methodology for the cutterhead and cutters was established in this study to achieve uniform wear of all cutters by the principle of frictional wear.The applicability of the design method was verified through three-dimensional simulations using the engineering discrete element method.The results show that uniform wear of all cutters on the cutterhead could be achieved by installing different numbers of cutters on each trajectory radius and designing a curved spoke with a certain arch height according to the shield diameter.Under the uniform wear scheme,the cutter wear coefficient is greatly reduced,and the largest shield driving distance is increased by approximately 47%over the engineering scheme.The research results indicate that the problem of nonuniform cutter wear in shield excavation could be overcome,thereby providing guiding significance for theoretical innovation and construction of long-distance shield excavation in highly abrasive strata.

A simplified two-dimensional boundary element method with arbitrary uniform mean flow

To reduce computational costs, an improved form of the frequency domain boundary element method（BEM） is proposed for two-dimensional radiation and propagation acoustic problems in a subsonic uniform flow with arbitrary orientation. The boundary integral equation（BIE） representation solves the two-dimensional convected Helmholtz equation（CHE） and its fundamental solution, which must satisfy a new Sommerfeld radiation condition（SRC） in the physical space. In order to facilitate conventional formulations, the variables of the advanced form are expressed only in terms of the acoustic pressure as well as its normal and tangential derivatives, and their multiplication operators are based on the convected Green＇s kernel and its modified derivative. The proposed approach significantly reduces the CPU times of classical computational codes for modeling acoustic domains with arbitrary mean flow. It is validated by a comparison with the analytical solutions for the sound radiation problems of monopole,dipole and quadrupole sources in the presence of a subsonic uniform flow with arbitrary orientation.

A UNIFORM HIGH-ORDER METHOD FOR A SINGULAR PERTURBATION PROBLEM IN CONSERVATIVE FORM

A uniform high-order method is. presented for the numerical solution of a singular perturbation problem in conservative form. We firest replace the original second-order problem (1.1) by two equivalent first-order problems ( 1.4), i.e., the solution of (1.1) is a linear combination of the solutions of (1.4). Then we derive a uniformly O (hm+1) accurate scheme for the first-order problems (1.4), where m is an arbitrary nonnegative integer, so we can get a uniformly O (hm+1) accurate solution of the original problem (1.1) by relation (1.3). Some illustrative numerical results are also given.

Trend surface analysis of forest landscape pattern in Guandishan forest region of Shanxi,China

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Research and application of uniform material counting method based on machine vision

Manufacturing and agricultural industries use manual methods to count materials. This leads to low accuracy and inefficiency. This paper proposes a secondary counting method that combines main and differential counting. The area-fill identification algorithm is applied to mark the counted materials. To verify the effectiveness of the proposed counting algorithm, numbers of countings are conducted for different materials, such as the screws, hole gaskets, beans, jujube, etc. The results show that the counting accuracy reaches 98% for materials with size of 2—20 mm. The method has delivered a high-efficiency and high-accuracy automatic intelligent counting, with a wide range of application prospects and reference value.

Optimization of H_2O_2 dosage in microwave-H_2O_2 process for sludge pretreatment with uniform design method

A microwave-H202 process for sludge pretreatment exhibited high efticiencies of releasing organics, nitrogen, and phosphorus, but large quantifies of H202 residues were detected. A uniform design method was thus employed in this study to further optimize H202 dosage by investigating effects of pH and H202 dosage on the amount of 1-I202 residue and releases of organics, nitrogen, and phosphorus. A regression model was established with pH and H202 dosage as the independent variables, and H202 residue and releases of organics, nitrogen, and phosphorus as the dependent variables. In the optimized microwave-H202 process, the pH value of the sludge was firstly adjusted to 11.0, then the sludge was heated to 80~C and H202 was dosed at a H202 ：mixed liquor suspended solids （MLSS） ratio of 0.2, and the sludge was finally heated to 100~C by microwave irradiation. Compared to the microwave-H202 process without optimization, the H202 dosage and the utilization rate of H202 in the optimized microwave-H202 process were reduced by 80% and greatly improved by 3.87 times, respectively, when the H202：MLSS dosage ratio was decreased from 1.0 to 0.2, resulting in nearly the same release rate of soluble chemical oxygen demand in the microwave-H202 process without optimization at H202：MLSS ratio of 0.5.

Integrated framework for seismic fragility assessment of cable-stayed bridges using deep learning neural networks

The increasing intensity of strong earthquakes has a large impact on the seismic safety of bridges worldwide.As the key component in the transportation network,the cable-stayed bridge should cope with the increasing future hazards to improve seismic safety.Seismic fragility analysis can assist the resilience assessment under different levels of seismic intensity.However,such an analysis is computationally intensive,especially when considering various random factors.The present paper implemented the deep learning neural networks that are integrated into the performance-based earthquake engineering framework to predict fragility functions and associated resilience index of cable-stayed bridges under seismic hazards to improve the computational efficiency while having sufficient accuracy.In the proposed framework,the Latin hypercube sampling was improved with additional uniformity to enhance the training process of the neural network.The well-trained neural network was then applied in a probabilistic simulation process to derive different component fragilities of the cable-stayed bridge.The estimated fragility functions were combined with the Monte Carlo simulations to predict system resilience.The proposed integrated framework in this study was demonstrated on an existing single-pylon cable-stayed bridge in China.Results reveal that this integrated framework yields accurate predictions of fragility functions for the cable-stayed bridge and has reasonable accuracy compared with the conventional methods.

Optimization of dosage ratio of chlorogenic acid and gardenia glycosides in the treatment of rats with fatty liver disease induced by high-fat feed

OBJECTIVE: To investigate the optimal dosage ratio of chlorogenic acid and gardenia glycosides in treating the rates with fatty liver disease induced by high-fat feed.METHODS: A rat model of non-alcoholic fatty liver disease(NAFLD) was established by using a high-fat diet. According to mathematical model "uniform design", varying doses of chlorogenic acid and gardenia glycosides have been combined to form 6 medications for the treatment of NAFLD.Samples were then taken to observe pathological changes of the liver tissue(HE staining); changes in the fat metabolism pathway e.g. triglyceride(TG)and free fatty acid(FFA) content; alterations in liver function, i.e. serum alanine aminotransferase(ALT)and aspartate aminotransferase(AST) activity; and differences in Malondialdehyde(MDA) and superoxide dismutase(SOD) content in the liver tissue. Multiple regression analysis was conducted to test the optimal dosage ratio of chlorogenic acid and gardenia glycosides.RESULTS: Fatty degeneration and vacuole-like changes of different degrees occurred in hepatic cells of the model group. Markers for fat metabolism, serum ALT and AST activities, and expression of MDA in liver tissue significantly increased, while SOD decreased. Combination of 90 mg chlorogenic acid and 90 mg Gardenia glycosides was the optimal dosage ratio of chlorogenic acid and gardenia glycosides in the treatment of rats with fatty liver induced by high-fat diet.CONCLUSION: Chlorogenic acid of 90 mg plus gardenia glycosides of 90 mg was the best combination in the treatment of fatty liver disease in rats induced by high-fat feed.