Advances in Science and Technology Vol. 166

Abstract: Stabilization of steel structure has always been a key concern in the engineering world. The phoenix shape of the upper station house in the ropeway project of Shaohuashan National Forest Park in Shaanxi Province consists of 5 groups of tube truss structures forming an overall space tube truss structure form through connecting rods. The finite element method was used to analyze its stability, and the overall structural eigenvalue buckling analysis and nonlinear instability analysis were carried out. It is shown that the factor of safety of the structure is inversely related to the initial defects under the consideration of the influencing factors of the initial defects. The instability modes of the structure are instability of the connecting rods connecting the five groups of tube trusses, instability of the bottom rods of the structure, and instability of the head rods of the skeleton.

Abstract: Tube truss structures are often used in large public buildings, and their safety performance under seismic effects is very important. The phoenix shape of the upper station house in the ropeway project of Shaohuashan National Forest Park in Shaanxi Province consists of 5 groups of tube truss structures forming an overall space tube truss structure form through connecting rods. The seismic response of this structure was analysed using the vibration mode decomposition response spectrum method. The results show that the overall structural vibration displacement changes in the first 10 vibration modes are concentrated in the head and the tail of each group of pipe truss structures; the internal force and displacement responses of the structure under seven different scenarios of multiple earthquakes are calculated, and the results show that the dynamic response of the structure is the largest under the unidirectional (X-direction) seismic action. The internal forces and displacements of structures under rare earthquakes are multiplicatively related to those under multiple earthquakes, and are closely related only to the coefficient of seismic influence.

Abstract: Many local governments currently require diesel-powered engineering machinery to be retrofitted with Diesel Particulate Filters (DPF) to reduce particle emissions. However, some machinery users remove or damage the filter in DPF to reduce maintenance costs, resulting in direct emission of particles into the air in the exhaust gases. This study proposes a method of using portable emission equipment to directly measure exhaust particulate matter to accurately assess whether the DPF is functioning properly. A comparison of the emission characteristics of particulate number concentration under high and low idle conditions was conducted in the study, revealing that measuring PN under high idle conditions can accurately identify whether the DPF in the machinery is functioning normally. At the same time, a comparison was made between the PN test results under high and low idle conditions and the current free acceleration smoke test results. It was found that machinery using electronic control systems cannot use the free acceleration smoke method to identify whether the DPF in the machinery has been damaged.

Abstract: In an open or unbounded system, when a solid sphere freely falls into a liquid, it accelerates until it reaches a terminal velocity. At this point, the gravitational force, buoyant force, and viscous drag acting on the sphere are balanced. Stokes' law describes that in a laminar flow state, the viscous drag on the sphere is proportional to its radius, velocity, and viscosity coefficient. In this paper, an experimental system was constructed and the vertical and horizontal positions of spheres were measured with different sizes and densities in liquids of different diameters and viscosities, and the vertical and horizontal positions, velocities, and accelerations of spheres were analyzed. The data analysis shows that the sphere is not only subjected to the viscous drag and but also the boundary forces from the system. This work will have a significance in modeling and computer simulation of accurate measurement of liquid viscosity.

Abstract: In this paper, a set of computer simulation techniques are put forward according to Helmholtz equation and the boundary conditions of the metallic circular waveguide, the different expressions on propagation modes of electromagnetic wave are given, and then the distribution rules of the tube-wall currents and charges are analyzed and discussed in different modes. The algorithm and techniques presented are helpful for the industrial application of measurements and design of the relevant devices.

Abstract: In order to carry out the analysis of the use safety of a small high-light detonation bomb, a simulation model of the bomb's explosive body was established based on the LS-DYNA platform. By simulating the burst process through LS-DYNA, the fragmentation distribution pattern and velocity variation were studied, and the kill radius of the projectile was evaluated. The results show that the bullet fragmentation size distribution is not uniform, and the large mass of low-velocity fragments generated in the middle of the explosive body is the main source of kill, and the kill radius is less than 1m. This study lays a theoretical foundation for the development and application of small high-light detonation bomb, and has a certain reference value for the research and design of the same type of ammunition.

Abstract: To meet the energy needs of devices such as wireless sensor networks and MEMS systems，improve the adaptability of piezoelectric energy harvester, this paper studies a two-degree-of-freedom(2-DOF) monostable piezoelectric energy harvester based on magnetic. The electromechanical coupling dynamics equation of the 2-DOF monostable system is established. The dynamic equation is solved by harmonic balance method. The output of dimensionless amplitude-frequency curves of a 2-DOF monostable piezoelectric system in the first and second order resonances is simulation analyzed. The results show that the output amplitude-frequency curve of the 2-DOF monostable system shows linearity of single peak value in the first-order resonance interval and hard spring characteristics in the second-order resonance interval. The research results provide reference for improving the energy harvesting efficiency and expanding the application in the radio field of piezoelectric energy harvester device.

Abstract: Based on the statistics of gas exceeding limit data in a high-gas mine in the southwest region in 2022, the big data method is used to analyze and summarize the regular characteristics of gas exceeding limit data from different dimensions such as the time of occurrence of the over-limit alarm, duration and maximum value. The analysis results show that the months with the most gas over-limit alarms are April, May and August, accounting for 41.66% of the total; the months with the least number of gas over-limit alarms are December, January and February, accounting for 12.09% of the total. . The highest number of alarms per day is at 1:00, 12:00 and 14:00, accounting for 17.69% of the total number; the lowest frequency is at 6:00, 7:00 and 15:00, accounting for 7.09% of the total number. Analyzed by the duration of the alarm, nearly 50% of the alarms are within 30 seconds. Comparing the maximum gas concentration during the alarm period, more than 85% of the alarm data have maximum values between 1.0 and 1.5. Analyzed by the area of occurrence, more than 80% of gas over-limit alarm accidents occurred in the three main operating areas of drilling construction, return air tunnels and transportation tunnels. Summarizing the analysis results, the mine strengthens gas safety prevention and control measures in the middle of each year, early morning and noon; focuses on dealing with over-limit alarms of more than 30 seconds, reducing the alarm duration, and reducing the number of high-concentration gas over-limits by stopping mining or strengthening ventilation. to reduce mine safety risks.

Abstract: Electrocardiogram (ECG) is the most commonly used diagnostic method for heart diseases such as arrhythmia. However, its inherent complexity, to some extent, reduces the accuracy of diagnosis. To quickly and automatically identify the type of arrhythmia, this paper constructs a clinical ECG classification model based on Convolutional Neural Network (CNN) to assist clinicians in analyzing ECG signals. The MIT-BIH ECG database is used as the research data source, and the heart beats are classified into 5 categories based on AAMI EC57 standard. 95% of the ECG data is randomly divided into training and testing sets, and the remaining 5% is used as the internal testing set. Based on the experimental outcomes, the model's accuracy exceeds 96%, indicating a commendable overall performance.

Abstract: Excessive carbon dioxide emissions are the primary factor causing global warming. Currently, models for controlling carbon dioxide emissions mainly focus on population, economy, and technology. A significant amount of research has been conducted on multivariate linear regression analysis encompassing factors such as population, GDP, and energy consumption. However, the studies examining the impact of green finance on emissions have been limited to qualitative and semi-quantitative levels, lacking in-depth and systematic research. This study establishes a composite model combining the Autoregressive Integrated Moving Average (ARIMA) model and Extreme Learning Machine (ELM) model. This composite model is employed to analyze the impact of Hubei provinces’ permanent resident population, GDP, comprehensive energy consumption, and green finance index on carbon dioxide emissions. In the ELM model, the impact of four variables-population, GDP, comprehensive energy consumption, and green finance index-on carbon dioxide emissions is investigated. Using data from 2002 to 2019, the ARIMA model is applied to predict these four variables after differencing. The ELM model's prediction of carbon dioxide emissions has a very small relative error compared to actual results. The composite mode- ELM-ARIMA model is used to analyze the province's carbon dioxide emissions from 2024 to 2030.