Research Object Research Articles

Initial temperature conduction process and fracture response of rock impacted by ultra-low-temperature fluid: A case study of polymethyl methacrylate

Injecting ultra-low-temperature fluids, such as liquid carbon dioxide (CO2) and liquid nitrogen (LN2), into deep, low-permeability reservoirs for fracturing is an emerging waterless fracturing technology. When these fluids enter the reservoir, they rapidly exchange heat with the fracture walls, triggering intense cold shock, which influences fracture development. Although many scholars have studied the effects of nitrogen freezing and thawing on coal seams, the initial thermal exchange and cold shock process when LN2 first enters the rock mass remains unclear. This paper uses the visualizable material polymethyl methacrylate (PMMA) as the research object, conducting low-temperature impact experiments under different preset temperatures (20 °C, 40 °C, 60 °C, and 80 °C) to investigate the impact of thermal exchange during cold shock on PMMA fracturing. The results show: (1) During LN2 impact, PMMA's temperature changes in three stages: slow cooling (micro-cracks initiation), rapid cooling (formation of long fractures), and temperature recovery (crack formation completion). (2) In prolonged impacts, PMMA temperature decreases linearly, while in short-term cyclic impacts, temperature decreases exponentially with faster recovery, increasing the likelihood of micro-cracks formation. (3) Temperature differences have a dual effect on crack formation and propagation: they significantly enhance internal thermal stress, leading to rapid micro-cracks initiation and expansion, while also causing uneven temperature gradients in the crack propagation region, shifting fracture modes from tensile to complex composite failures and promoting secondary crack formation. However, a significant temperature differential may result in the development of a singular crack propagation path, hindering the formation of complex fracture networks. These findings offer theoretical insights into fracture network formation in waterless fracturing of low-permeability reservoirs.

Gu Sui Bu (Drynaria fortunei J. Smith) prevents osteoporosis in ovariectomized rats by inhibiting pyroptosis through NLRP3/GSDMD/CASPASE-1

Traditional Chinese medicine Gu Sui Bu (Drynaria fortunei J. Smith) has the effect of tonifying the kidneys and strengthening bone. There are many modern studies on the anti-osteoporosis pharmacological mechanism of Drynariae, but no reports on the pharmacological mechanism of Drynariae improving cell pyroptosis and anti-osteoporosis have been found. AimThis study aims to verify the changes in cellular standard indicators in postmenopausal osteoporosis, thereby revealing the participating mechanism of pyroptosis and the intervention effect of Gu Sui Bu (Drynaria fortunei J. Smith) . MethodsDrynariae was subjected to UHPLC-Q-Orbitrap-MS/MS analysis, and the OVX rat model was constructed in vivo as the research object. It was divided into sham operation group (SHAM), ovariectomized osteoporosis model group (OVX) and bone fragmentation. Supplementary drug group (TFRD-L, TFRD-H). After 3 months of modeling, the medication group was treated with Drynariae and the samples were collected after 12 weeks of intervention. ELISA was used to detect the levels of Caspase-1, NLRP3, GSDMD, IL-1β, and IL-18 in rat serum; the right femur was taken for Micro-CT large bone microstructure scanning and femoral BMD detection; the femur was subjected to rat histopathology HE, TRAP staining; immunohistochemistry and immunofluorescence staining of rat histopathology were performed. WB and PCR were used to observe the expression of cell pyroptosis-related indicators Caspase-1, NLRP3, GSDMD and RUNX2, IL-1β, and IL-18. ResultsUHPLC-Q-Orbitrap-MS/MS analysis the main compounds in Gu Sui Bu (Drynaria fortunei J. Smith) samples were identified. These 9 chemical components are Palmitic acid, Fisetin, Caffeic acid, Naringin, Rutin, Uridine, Cafestol, Astilbin . Rat Micro-CT, The results of HE staining and TRAP showed that compared with the rats in the OVX group, the number of bone trabeculae in the rats in the Gu Sui Bu (Drynaria fortunei J. Smith) medication group (TFRD-L, TFRD-H) increased, became wider and thicker, and the bone density increased. Continuity increases and bone lacunae decrease. Rat serum ELISA, femoral tissue immunohistochemistry, immunofluorescence staining and WB, PCR showed that compared with the OVX group, Caspase-1, NLRP3, The expression levels of GSDMD and inflammation were reduced (p<0.05), and the expression of osteogenic marker RUNX2 was reduced and increased (p<0.05). ConclusionThe traditional Chinese medicine Gu Sui Bu (Drynaria fortunei J. Smith) can improve the bone density of ovariectomized osteoporosis model rats and significantly enhance the bone microstructure. At the same time, it reduced the expression of rat cell pyroptosis markers Caspase-1, NLRP3, and GSDMD in vivo, confirming that Gu Sui Bu (Drynaria fortunei J. Smith) may play an anti-osteoporosis effect through the NLRP3/GSDMD/Caspase-1 pathway.

Microplastics influence nutrient content and quality of salt-affected agricultural soil under plastic mulch.

Northeast China is an important food production base and plays a crucial role in national food security. However, the increase in salt-affected soils poses a challenge to agricultural production in this region. Plastic mulching is an effective technique for saline cropland improvement, and although it has increased crop yields in the short term, its long-term application may have introduced the problem of contamination by microplastics (MPs). The distribution of MPs in salt-affected cropland, along with the effects on soil nutrients, remains largely unknown. Accordingly, the presented research selected salt-affected cropland as the research object, after which MPs were quantified from 46 soil samples from currently mulched and unmulched fields. MPs abundance in the sampled soils ranging from 4.10×103∼1.50×104 particles per kilogram of dry soil. The detected MP polymers were mainly high-density polyethylene (46%), polypropylene (22%) and polyvinyl chloride (20%). The MP particles most commonly fell under the size ranges of 50∼100 μm (35%) and 100∼200 μm (28%), both of which are small particle sizes. The most commonly detected MP shapes were film (34%) and fragment (31%). The mulched samples from salt-affected cropland generally showed higher soil nutrient contents than the unmulched samples. Moreover, MP abundance, type, size, and shape all demonstrated strong correlations with soil organic carbon and total nitrogen. MP type is a major factor determining soil nutrient content. Plastic mulching serves as an important source of MPs in salt-affected cropland, with these contaminants affecting nutrient content. Future research should be broader in scope and include ecological benefits and policy implications, with a view to optimizing the problem of MPs contamination due to mulching.

Simultaneous image denoising and completion through convolutional sparse representation and nonlocal self-similarity

Low rank matrix approximation (LRMA) has been widely studied due to its capability of approximating original image from the degraded image. According to the characteristics of degraded images, image denoising and image completion have become research objects. Existing methods are usually designed for a single task. In this paper, focusing on the task of simultaneous image denoising and completion, we propose a weighted low rank sparse representation model and the corresponding efficient algorithm based on LRMA. The proposed method integrates convolutional analysis sparse representation (ASR) and nonlocal statistical modeling to maintain local smoothness and nonlocal self-similarity (NLSM) of natural images. More importantly, we explore the alternating direction method of multipliers (ADMM) to solve the above inverse problem efficiently due to the complexity of simultaneous image denoising and completion. We conduct experiments on image completion for partial random samples and mask removal with different noise levels. Extensive experiments on four datasets, i.e., Set12, Kodak, McMaster, and CBSD68, show that the proposed method prevents the transmission of noise while completing images and has achieved better quantitative results and human visual quality compared to 17 methods. The proposed method achieves (1.9%, 1.8%, 4.2%, and 3.7%) gains in average PSNR and (4.2%, 2.9%, 6.7%, and 6.6%) gains in average SSIM over the sub-optimal method across the four datasets, respectively. We also demonstrate that our method can handle the challenging scenarios well. Source code is available at https://github.com/weimin581/demo_CSRNS.

Research on design method of lattice turbine disk based on topology optimization

Abstract As a typical structure of an aero-engine, turbine disk has been used in high-temperature and high-speed environments for a long time, and its mass accounts for a large proportion. Therefore, its lightweight design is urgent. With the development of an aero-engine towards a high thrust-to-weight ratio, the turbine speed continues to increase, and the single-stage load continues to increase, which makes the design of the turbine disk face more problems and challenges. The uniform material turbine disk structure has made it difficult to meet its comprehensive performance requirements. To address this issue, this paper proposes a lattice turbine disk design idea, changing the uniform organization pursued by traditional design and achieving optimal performance through the integration of design innovation and manufacturing process innovation. This paper takes the turbine disk as the research object to establish a lattice turbine disk design method. By using the topology optimization method based on progressive optimization, the cell configuration can be obtained. After that, combined with the structural characteristics of the turbine disk, the design of the dot matrix auxiliary plate disk is realized. Finally, taking a turbine disk as an example, this paper carried out the optimization design of the turbine disk and obtained the lattice disk with better performance, which verified the feasibility of the method.

The influence of tax burden, intangible assets, and foreign ownership on transfer pricing policies

This research aims to determine and empirically test the influence of tax burden, intangible assets and foreign ownership on transfer pricing policies in energy sector companies listed on the Indonesia Stock Exchange (BEI) during the 2018 2022 period. This type of research is descriptive quantitative which uses secondary data sourced from the company's financial reports that have been published by the company on the Indonesia Stock Exchange (BEI). This research consisted of 84 companies and the number of samples used was 9 companies as research objects for five years. The data analysis technique for testing this hypothesis uses E-views 12 software. Panel data regression analysis is used as the mechanism in this research. The research results show that the tax burden has a significant effect on transfer pricing. Meanwhile, intangible assets and foreign ownership do not have a significant effect on transfer pricing. This is because companies can consider tax burdens, intangible assets and foreign ownership in transfer pricing policies

Optimization of Composite Wheel Fender for Manned Lunar Vehicle

Abstract Weight reduction is the eternal theme of aerospace optimization. In the process of weight reduction, the main ways are material change, structural change, and processing method change. In the process of aerospace structure design, the boundary and load conditions are more complicated, which restricts the development of optimization technology in the aerospace field to some extent. At present, the research object of optimization technology in the aerospace field is mainly the large parts of the aerospace craft, and the structural optimization of small aerospace parts is rarely involved. Therefore, the research of structural optimization design method has important theoretical and engineering significance. A complete optimization design process is proposed, the structural performance of aviation products is simulated by finite element software, and the feasibility of the optimization theory is verified. This article mainly compares several schemes for weight reduction design of composite material wheel fenders in the process of design.

Characteristics of constant pressure dehydrogenation and construction of linear diffusion model for solid hydrogen storage materials: A case study of TiMn1.5 alloy

Solid-state hydrogen storage is considered to be the most promising hydrogen storage technology because of its high volumetric capacity and good security. The process of hydrogenation and dehydrogenation of solid hydrogen storage materials can be characterized by a diffusion kinetic model, which can be used to guide the safe and efficient application of hydrogen storage materials. Currently, experimental study on the dehydrogenation characteristics under constant pressure outer boundary condition has not been carried out methodically, and a simple and reliable diffusion kinetic model under this condition should be established based on the experimental results. In this study, an experimental platform for hydrogen absorption and constant pressure dehydrogenation of solid hydrogen storage materials was independently established. The TiMn1.5 alloy and its interstitial hydrides were taken as the experimental research objects to conduct constant pressure dehydrogenation tests, and the dehydrogenation properties at different temperatures were systematically studied. The results show that the dehydrogenation rate decreases with the increase of testing time. The ultimate capacity of hydrogen release increases first and then decreases with the increasing temperature, reaching the maximum value at 30 °C. It is found that the diffusion coefficient increases linearly with time during constant pressure dehydrogenation process. On this basis, a linear diffusion kinetic model is established. The initial diffusion coefficient D0 calculated by the new model has a quadratic polynomial relationship with temperature, and the increase coefficient α of diffusion coefficient has a linear relationship with temperature. According to the mathematical expressions, the dehydrogenation process of TiMn1.5 alloy at different temperatures can be predicted. The research results can provide theoretical guidance for the safe, efficient and controllable application of hydrogen storage materials.

THE NEED OF PRODUCING OF PROFESSIONAL CODE OF ETHICS FOR GUIDES IN LITHUANIA

Research problem: Ethical issues is not a much studied topic in the field of guides' professional activity. Lithuanian guides do not have an established Professional Code of Ethics for Guides. The topic of Guide Ethics depends on the personal responsibility of a guide. What ethical principles and values should guide the Guide in professional activities? How can guides agree on unified ethical requirements for professional activity? Research object: the Need of Producing of Professional Code of Ethics for Guides in Lithuania. Research aim: to analyse the Need of Producing of Professional Code of Ethics for Guides in Lithuania. Research methods: analysis of scientific literature and documents, qualitative research – interviews, quantitative research – survey, systematization of databases. Conclusions. It is important to have a Code of Ethics for every organisation striving for effective communication. In addition to other knowledge, a Guide must know professional ethics, represent the country professionally and responsibly. The results of quantitative and qualitative research substantiate the Need of Producing for a Professional Code of Ethics for Guides in Lithuania. The quality of services provided by the tour guide, impeccable preparation and conduct of the tour, the visual image of the tour leader, and cultural behaviour are important for those who book tours. Most of the guides who took part in the study are in favour of Producing the Professional Code of Ethics for Guides in Lithuania. Based on the results of the conducted research, the main ethical principles of the guide's professional activity were highlighted. It is recommended to organize trainings for guides on the topic of professional ethics, to prepare a draft of Professional Code of Ethics for Guides and to present the draft of the Professional Code of Ethics for Guides to Lithuanian guides; to initiate Producing and Implementation of the Professional Code of Ethics for Guides in Lithuanian guide associations.

Effects of Rainfall Variability and Land Cover Type on Soil Organic Carbon Loss in a Hilly Red Soil Region of Southern China

Rainfall intensity (RI) and land cover type are two important factors that affect soil erosion and thus the transfer and loss of soil organic carbon (SOC). However, the in situ quantitative monitoring of SOC loss under natural rainfall and various land cover types restored on eroded lands has not been thoroughly examined. In order to further study the effects of rainfall changes and vegetation types on SOC loss in the red soil region of Southern China, the Jiangxi Eco-Science Park of Soil and Water Conservation in De’an County, Jiangxi Province, was taken as the research object. Considering natural rainfall and based on the long-term field in situ monitoring of rainfall and runoff and sediment data, we studied the effects of three land cover types (bare land, orchards, and grass cover) on surface runoff, sediment production, and SOC loss in relation to 1 hour of RI during natural rainfall in the red soil region of Southern China during rainy seasons of 2020 and 2021 (March to August). Compared with bare land plots, the orchard and grass cover plots had surface runoff reductions of 67% and 98%, respectively, and sediment reductions of 79% and 99% over the two rainy seasons, respectively. With an increasing RI over 1 hour, total SOC loss increased for each of the three land cover types. More SOC loss was associated with sediments, and the enrichment ratio of SOC in the sediments (ERoc) decreased significantly. The ERoc values decreased in the following order: bare land (1.23) &gt; orchard (1.08) &gt; grass cover (0.81). Bare land exhibited the highest proportion of SOC associated with sediment in the total SOC loss (Ps), at 68.69%, followed by the orchard plots, at 55.02%, and then the grass cover plots at 49.24%. With the transfer of land cover type from bare land to orchard and to grass cover (decreased soil loss intensity, SLI), more SOC was lost associated with runoff in the form of dissolved organic carbon (DOC); the values of ERoc and organic carbon loss intensity (CLI) also decreased significantly. These findings are crucial to improving our understanding of the regulatory mechanisms of rainfall changes and land cover types on SOC loss during soil erosion.

Ship Power System Network Reconfiguration Based on Swarm Exchange Particle Swarm Optimization Algorithm

As one of the important components of a ship, the ship’s integrated power system is an important safeguard for ships. In order to improve the service life of the ship’s power grid, the power system should be able to realize rapid reconstruction to ensure continuous power supply of important loads when the ship is attacked or fails suddenly. Therefore, it is of vital importance to study the reconfiguration technology of the ship’s integrated power system to ensure that it can quickly and stably cope with all kinds of emergencies in order to guarantee the safe and reliable navigation of the ship. This paper takes the ship’s ring power system as the research object and sets up the maximum recovery load and the minimum number of switching operations. The load is divided uniformly and the generator efficiency is balanced for the reconstruction of comprehensive function. It also sets up the system capacity, topology, and branch current limitations of the constraints to establish a mathematical model. The load branch correlation matrix method is used for branch capacity calculation and generator efficiency equalization calculation, and the load backup power supply path matrix is added on the basis of the matrix to judge the connectivity of some loads before reconfiguration. In this paper, for the network reconfiguration of the ship circular power system, which is a discrete nonlinear problem with multiple objectives, multiple time periods, and multiple constraints, we choose to use the particle swarm algorithm, which is suitable for global optimization, with a simple structure and fewer parameters; improve the particle swarm algorithm using the swarm exchange strategy by setting up two main and auxiliary swarms for global and local search; and exchange some of the particles with the golden ratio in order to keep the diversity of the populations. The simulation results of the network reconfiguration of the ship power system show that the improved algorithm can solve the power system network reconfiguration problem more effectively and provide a feasible reconfiguration scheme in a shorter time compared with the chaotic genetic algorithm under the same fault case test, and it also proves that the use of the swarm exchange particle swarm algorithm greatly improves the performance of reconfiguring the power grid of the ship.

Study on Coal Seam Roof Failure Based on Optical Fiber Acoustic Sensing and the Parallel Electrical Method

As China enters the stage of deep coal mining, the accidents caused by roof failure pose increasingly serious threats. Current research on roof failure zones often use single methods, but single geophysical data may result in multisolution issues during interpretation. This paper employed similar simulation experiments, exploring the strain failure characteristics and the changes in apparent resistivity caused by stress variations, taking the 11-3106 working face of a mining area as the research object. Through optical fiber strain and apparent resistivity, the locations and degrees of fracture in postmining rock strata were identified. The feasibility of using distributed optical fiber sensing and the parallel electrical method for qualitative and quantitative analysis of mining-induced fractures was verified. The results showed that optical fiber strain increased significantly at the location of rock fracture, with apparent resistivity anomalies rising correspondingly. The peak strain region corresponded well with the region of apparent resistivity anomalies. In a similar simulation with a geometric ratio of 1:100, the height of the caving zone was measured to be 31.65 cm, with a caving-to-mining ratio of 6.33. In the field working face, the caving zone height was 29.47 m, with a caving-to-mining ratio of 6.01, consistent with the actual conditions of the 11-3106 working face.

Comprehensive Evaluation Research on the Sustainable Development Level of Rural Energy Based on CRITIC-MABAC in Henan Province

Energy shortages are a key issue at present, and climate problems caused by the extraction and use of traditional fossil energy sources are also creating new challenges for rural development, with sustainable rural energy development being a priority at present. This paper takes the sustainable development of rural energy as the research object, and evaluates the development of rural energy in each prefecture-level city in Henan Province. On the one hand, rural development is viewed from the perspective of energy, on the other hand, the evaluation results provide a reference for each prefecture-level city, and most of the energy data can be obtained directly and with a high degree of accuracy, based on the CRITIC – MABAC methodology to determine the weights from an objective point of view and to rank the evaluation results, which is capable of obtaining the most accurate evaluation results. Finally, we used energy-related data from Henan Province in 2022 to conduct empirical analyses, and verified that Shangqiu City has a high level of sustainable rural energy development, which verifies the feasibility of the methodology proposed in this paper, and gives relevant recommendations.

Research on the Female Media Image Shaping of the Mainstream Media

In this paper, the articles on WeChat official account Southern Weekend are taken as the research object, using a content analysis method and focusing on the female media image-building in the mainstream media. It is found that the female image construction in mainstream media is still influenced by historical culture, patriarchal culture, and other factors, and there are hidden prejudices, inequalities and imbalances, which do not correctly guide the shaping of female media images from the root.

The Analysis and Compensation Experiment of Linear Feed Axis Positioning Error Based on Matrix Operation

The positioning accuracy of the linear feed axis is a key factor affecting the machining accuracy of CNC machine tools. The generation process of the positioning error of the linear feed axis is expounded. The Z axis of the vertical linear feed axis of the machining center is the research object, the positioning error analytical matrix is established, and the positioning error calculation of the Z axis of the vertical linear feed axis is completed based on the principle of solving the inhomogeneous linear equation. The positioning error detection of the vertical linear feed axis Z axis of the CNC machining center is carried out. Based on the characteristics of the error detection data, an error compensation model is constructed. , the variance of the positioning error detection point after compensation is reduced to 1.562, which meets the needs of precision machining.

An Empirical Analysis of Carbon Emissions in Higher Education Institutions: A Case Study of Zhejiang Ocean University Using Emission Factor Methodology

In recent years, with the increase in greenhouse gas emissions, global warming has created a series of complex ecological challenges. Colleges and universities are still in the exploratory stage of constructing low-carbon campuses. This study takes the campus of Zhejiang Ocean University as the research object and obtains carbon emission data from it based on the emission coefficient method by visiting the site and issuing a questionnaire survey. A total of 246 questionnaires were collected in this study, which were quantitatively analyzed to further understand the composition of the carbon emission structure of universities and put forward the corresponding energy-saving and emission-reducing suggestions. This study actively responds to the national call for energy saving and emission reduction and aims to provide a data reference as well as scientific support for the construction of a low-carbon campus. The results show that in 2021, the carbon emissions of Zhejiang Ocean University were 3.39 × 107 kg, of which direct carbon emissions were 3.34 × 105 kg, accounting for 0.99% of the total carbon emissions; indirect carbon emissions were 1.50 × 107 kg, accounting for 44.33% of the total; and other indirect carbon emissions were 1.85 × 107 kg, accounting for the remaining 54.68%. Also, this study found that individuals in colleges and universities pay attention to carbon emissions, but it is difficult for them to maintain a low-carbon approach in daily life. Based on the results of the analysis, this study proposes a series of effective measures to reduce carbon emissions at the campus of Zhejiang Ocean University, unite students in colleges and universities, and fully implement the concepts of energy saving, emission reduction, and sustainable development in college life.

Active Disturbance Rejection Control for Flux Weakening in Interior Permanent Magnet Synchronous Motor Based on Full Speed Range

To address the impact of load disturbances on the full-speed-range control of an interior permanent magnet synchronous motor (PMSM), an active disturbance rejection control (ADRC) method is proposed. The speed loop employs phased field-weakening control (FW) based on ADRC, while the current loop utilizes proportional-integral-derivative (PID) control. Starting from the motor parameters, the Lagrange multiplier method was used to derive the critical speeds for the maximum torque per ampere (MTPA) and maximum torque per voltage (MTPV) ratios, and the timing for the field-weakening control was analyzed. A full-speed-range control model of the motor was established, and an ADRC-based speed loop controller was designed to achieve smooth transitions between high speeds and anti-disturbance solid capabilities. Based on the proposed control strategy, a 21 kW PMSM was used as the research object, and a full-speed-range control simulation model was developed in MATLAB/SIMULINK to verify the strategy. Compared to the traditional PID control, the simulation results demonstrate that the proposed strategy effectively observes and compensates for load disturbances, significantly reducing initial torque oscillations under three different operating conditions. After a sudden load increase, torque oscillations were reduced by 16%, with the stator current reaching steady state 0.03 s faster, response speed improving by 0.02 s, smooth transitions between speed ranges, and enhanced anti-disturbance performance.

Architectural Modernisation in Panevėžys During the 1930s: Exploring the Works of Civil Engineer Antanas Gargasas

Summary In contemporary studies of Lithuanian interwar architecture, so far the greatest attention is paid to the analysis of the architectural development and modernization processes that took place in the city of Kaunas, the temporary capital of the country at the time. The work of architectural specialists who worked there is also analysed more. However, at the same time, little is known about the development of architecture created in the smaller cities of Lithuania at that time and its modernization. Thus, this article aims to more thoroughly reveal and analyse the processes of modernization of Panevėžys city architecture that took place in the 1930s, choosing the designs of Antanas Gargasas, who worked there as a municipal engineer in 1931–1940, as the research object. This is done in the article by analysing and presenting the majority of his designed public buildings and the most significant and typical residential buildings. The article, which was written based on archival material, the press of the research period and the contemporary studies of the interwar architecture, contains an assumption that the buildings designed by Antanas Gargasas had a significant influence on the processes of modernization of the Panevėžys architecture at that time and the spread of new stylistic trends in it. The article is supplemented by the drawings and photos of the buildings designed by the engineer.

Hopf Bifurcation Analysis of a Nose Landing Gear System of Aircraft

The Hopf bifurcation problem of a nose landing gear system is investigated. Taking the nearly smooth landing gear system with high-order nonlinear terms as the research object, the nose landing gear system is simplified to a plane dynamic system considering nonlinear factors by using the center manifold simplification method. The first Lyapunov coefficient of the landing gear system is derived by using the classical bifurcation theory, and the Hopf bifurcation type of the system is determined according to its sign. The bifurcation diagram is obtained by solving the differential equations of motion numerically. It is revealed that there is a stable limit cycle in the neighborhood of the supercritical Hopf bifurcation point. The influence of velocity and other factors on the shimmy oscillations of the landing gear system is analyzed. The dynamical behavior in the neighborhood of the Hopf bifurcation point is explored theoretically and numerically. The research results can provide a theoretical basis for the optimal design of aircraft landing gear systems.

Effects of Biochar and Nitrogen Fertilizer Application Ratio on Leaf Physiology and Soil Characteristics of Bambusa tuldoides ‘Swolleninternode’

As one of the main bamboo species in coastal sandy land protection forests, Bambusa tuldoides ‘Swolleninternode’ can effectively improve the structure of forest tree species, increase the diversity of tree species and enhance the protection efficiency. However, research on the cultivation and utilization of B. tuldoides is still relatively scarce. Therefore, in this study, B. tuldoides was used as the research object. By applying biochar and nitrogen fertilizer, the effects of different biochar and nitrogen fertilizer ratios on the physiology and soil characteristics of bamboo were analyzed, and the optimal ratio scheme was identified. The results showed that the ratio of the T5 (A2B2C3) treatment had the best effect on the total chlorophyll, non-structural carbohydrate and nutrient contents of B. tuldoides leaves, and the contents under treatments was generally higher than under the control, CK. The activities of soil invertase, nitrate reductase and nitrite reductase were significantly increased under biochar treatment, and the effects of the T5 treatment were the best. The results of principal component analysis showed that the absolute values of the coefficient of leaf potassium, phosphorus content and soil total nitrogen were larger and more important, and the comprehensive evaluation of the T5 treatment was the highest.