Frost damage is a key problem in the construction of alpine tunnels. A numerical model was established to consider heat conduction and convection for designing effective thermal insulation measures. Orthogonal test conditions were designed to analyze the significance of different thermophysical parameters on lining temperature and their influence on lining damage. The results show that the convection coefficient, the thermal conductivity of the insulation layer, and the thermal conductivity of the surrounding rock have significant influences. The thermal conductivity of the insulation layer has the most significant impact. As its thermal conductivity increases, the lowest lining temperature decreases, and the damage level increases. An increase in the convection coefficient decreases the minimum lining temperature and increases damage. Higher thermal conductivity of surrounding rock raises the minimum lining temperature, spreading damage from the vault to the sides. Reducing the thermal conductivity and convection coefficient of the insulation layer, while increasing the thermal conductivity of the surrounding rock, improves overall damage distribution.

To investigate the mechanism and influencing factors of soil heating with coupled in situ thermal technology, a two-dimensional experimental setup was used to simulate the heat treatment process, and the effects of coupled steam injection on thermal conductive heating as well as the effects of steam injection rate and heating mode on the application of the thermal conductive heating and steam injection technology were investigated. The results show that coupling steam injection on the basis of thermal conductive heating treatment can accelerate heat transfer, reduce heat loss, shorten the heating time by 35.67%, and reduce energy consumption by 24.53%. The main mechanism of steam injection enhanced heating is as follows. The additional heat injection increases the temperature difference, which in turn enhances convective heat transfer in the liquid phase driven by buoyancy. The upward migration of steam under buoyancy or pressure to enhance convective heat transfer in the gas phase. In thermal conductive heating and steam injection treatment, changing the steam injection rate or heating mode had a small effect on the treatment energy consumption, increasing the steam flow rate from 0.18 to 0.54 kg/h can shorten the heating time by 22.05%, but increase the water consumption by 132.43%. Compared with the thermal conductive heating and steam injection heated at the same time, thermal conductive heating heated for 30 min and then coupled with steam injection can reduce the water consumption by 28.57%, but will extend the heating time by 3.84%. In engineering applications, suitable restoration solutions should be selected based on duration, cost, etc.

Aiming at the problems of poor disturbance immunity and long dynamic response time of the grid-connected inverter based on VSG(virtual synchronous generator) control, an improved fuzzy adaptive control strategy for VSG was proposed. First, a small-signal model of VSG was established to analyze the effects of virtual inertia and damping coefficient on the dynamic response of the system. Determine the value range of the two parameters and use the sparrow search algorithm to optimize the initial values of inertia and damping in the adaptive strategy. Next, the angular frequency change curve of the system after perturbation was analyzed to refine the design fuzzy rules. Finally, a stand-alone VSG model was built in MATLAB/Simulink to compare the different control strategies. The results show that the fuzzy adaptive strategy proposed in this paper not only improves the response speed of the system, but also has a strong anti-disturbance ability when the command power and load power change suddenly. The effectiveness of this paper's strategy is proved.

As an important firefighting equipment, fire cylinders need to undergo regular safety evaluations during their service period. In order to efficiently and accurately evaluate the safety status of fire steel cylinders, a safety evaluation model suitable for fire steel cylinders was established based on the analytic hierarchy process and fuzzy comprehensive evaluation method. The feasibility of the model was verified through case evaluation. Secondly, the BP neural network based on MPGA (multi population genetic algorithm) is used to optimize the safety evaluation model of fire steel cylinders. This method improves the process of updating weights and thresholds of the BP neural network through multi population genetic algorithm, improving the accuracy of BP neural network prediction results and the efficiency of fire steel cylinder safety evaluation. Finally, the construction of safety evaluation models for fire steel cylinders based on BP, GA-BP, and MPGA-BP was completed using Python. By comparing and analyzing the prediction results of three models, it was found that the MPGA-BP neural network has the smallest prediction error, proving that the proposed MPGA-BP safety evaluation model has high accuracy and can more efficiently and accurately evaluate the safety of fire steel cylinders.

A method for diagnosing AC series arc faults based on the Inception module and BiLSTM (bidirectional long short-term memory) was proposed to address the challenge of identifying small current changes caused by arc faults in aviation cables. First, features of the raw current data were extracted by calculating the discrete sum of squares of the autocorrelation coefficient, Shannon entropy, and wavelet energy entropy. These features are then combined to form a new feature matrix, enhancing the original data's feature representation. Subsequently, the Inception-BiLSTM network learns from the feature matrix and ultimately completes the arc fault diagnosis. To validate the diagnostic performance of the model in practical environments, a series of experiments were conducted, including vibration tests, stress tests, and wet cable tests, based on an aviation cable arc fault simulation platform, with the experimental data being integrated as detection samples. The experimental results show that the proposed method achieves a high accuracy rate of 99.69% in identifying arc faults.

In order to investigate the heat and mass transfer of liquid droplet impinging on a heated surface with different wettability, VOF(volume of fluid) numerical simulation method was used to analyzed the mechanisms of wall wettability and surface temperature on droplet morphology and heat transfer characteristics. The results show that the hydrophilic wall is favorable for droplet spreading, while the hydrophobic wall is favorable for droplet rebound. With the increase of contact angle, the maximum spreading factor of droplets decreases, the time to reach the maximum spreading factor is shortened, and the average heat flux of the wall surface decreases. Surface temperature has less influence on the droplet spreading stage, with the increase of surface temperature, the droplet phase transition rate accelerates, the average heat flux of the wall surface increases, and the Leidenfrost phenomenon occurs when the surface temperature exceeds the critical temperature.

Wood consists of a number of early and latewood alternately, in order to predict the strength of the mechanical properties of the specimen according to the proportion of early and latewood, a composite material model with early and latewood as the basic modeling unit was established. Starting from the fine level of wood, the wood is regarded as a composite material ideally bonded by two kinds of materials with different mechanical properties of early and late wood. Taking Yunnan pine as the research object, the respective mechanical parameters of early and late wood were obtained respectively, and according to the theory of composite plywood, the composite material tensile strength model of early and late wood with smooth grain was set up, and the test is utilized to verify the results. The results show that it is feasible to consider the wood as early and latewood composite material and use the laminate theory to predict its mechanical properties. The relative errors between the theoretical values of tensile elastic modulus and tensile strength and the experimental values are within 10%, which is highly reliable, and according to this model, the tensile strength and elastic modulus can be calculated through the measurement of the volume fraction of the latewood in the material, which will provide a good basis for the subsequent early and latewood tests and the further study of the early and latewood related models. This model can provide a reference basis and theoretical foundation for the in-depth study of the subsequent early and late material test and the related model of early and late material.

Tahe Oilfield was one of the important oilfields in western China. The monitoring and development of remaining oil reserves were paid significant attention to and were regarded as one of the current challenges in oil and gas exploration and development. Well-to-surface time-frequency electromagnetic detection technology, due to its sensitivity to oil-gas-water interfaces, was increasingly applied in oilfield development. However, as time-frequency electromagnetic detection technology was introduced relatively late in oil and gas detection, the related detection mechanisms and high-resolution signal extraction and interpretation were still under research. Through the analysis of well-to-surface time-frequency electromagnetic exploration principles, a technical sequence for differential apparent resistivity, differential phase processing, and imaging analysis of well-to-surface time-frequency electromagnetic data was established, starting from the definition of regional apparent resistivity. The differential processing results of time-frequency electromagnetic data collected from the actual production well TX1 in Tahe Oilfield demonstrated that the high-density sampling provided by multi-pole transmission and multi-frequency reception of well-to-surface time-frequency electromagnetic detection technology offered high-resolution reservoir detection datasets. The new differential data processing technology could greatly enhance the effective identification capability of deep oil-gas-water interfaces. The successful trial of this method provided a promising technical means for oil-gas-water detection in oilfield development. Additionally, through comparative analysis with seismic exploration results, it was found that well-to-surface electromagnetic exploration had unique advantages in identifying complex underground structures and could provide complementary information to seismic exploration.

Aiming at the problem that ViBe (visual background extractor) algorithm is prone to ghosting during moving target detection, an improved algorithm, ViBe-BR (ViBe with background restoration) was proposed by adding a background restoration stage to the original algorithm. First, the foreground region within the background image was pre-extracted by combining three-frame differencing. Then, the interior of the region was filled using the background pixels around the foreground region to obtain the restored image; Finally, the restored image was corrected and ViBe detection was performed based on the reduced background to achieve the effect of suppressing ghosting. The experimental results show that the ViBe-BR algorithm achieves good detection results in four different scenes, and compared with the ViBe algorithm, the average precision, recall, and F₁ value of foreground detection have been improved by 0.222, 0.03, and 0.123 in that order, which effectively eliminates the influence of ghosting, and it can be applied to practical geo-localization tasks in order to obtain the geographic location information of the moving targets.

China's deep coalbed methane resources have enormous potential. As a clean and high-quality energy, it is of great significance to ensure China's energy security and green and low-carbon development. The development of middle-shallow coalbed methane in China has basically been industrialized, but the development scale is far from the national planning goal. With the new progress made in the exploration and development of deep coalbed methane in recent years, it has provided new impetus for the rapid development of the coalbed methane industry. But when it comes to deep exploration and development, it faces a series of new geological, engineering, and other challenges that need to be tackled. In view of this, based on the latest national oil and gas resource evaluation data, the current situation of coalbed methane exploration and development in China was summarized, and the latest progress in deep coalbed methane exploration and development in typical blocks in China was evaluated. The new breakthroughs in geological evaluation, drilling, fracturing, and extraction of deep coalbed methane in recent years were summarized, and it is pointed out that there are problems in the current exploration and development of deep coalbed methane in China, such as low resource evaluation level, low adaptability of key technologies, and few mature demonstration projects that can be promoted and referenced.On this basis, four countermeasures and suggestions for the development of deep coalbed methane industry were proposed: strengthening resource exploration, strengthening key technical research, speeding up the construction of high-efficiency development demonstration zones, strengthening the co-exploration and co-exploitation of deep coal measures gas, so as to provide reference for promoting the exploration and development of deep coalbed methane in China.