Search Results (82)

Numerical modelling of airflow in underground mines is gaining importance in modern ventilation system design and safety assessment. Computational Fluid Dynamics (CFD) simulations enable detailed analyses of air movement, contaminant dispersion, and heat transfer, yet their reliability depends strongly on the accuracy of the geometric representation of excavations. Raw point cloud data obtained from laser scanning of underground workings are typically irregular, noisy, and contain discontinuities that must be processed before being used for CFD meshing. This study presents a methodology for automatic segmentation and regularization of large-scale point cloud data of underground excavation systems. The proposed approach is based on skeleton extraction and trajectory analysis, which enable the separation of excavation networks into individual tunnel segments and crossings. The workflow includes outlier removal, alpha-shape generation, voxelization, medial-axis skeletonization, and topology-based segmentation using neighbor relationships within the voxel grid. A proximity-based correction step is introduced to handle doubled crossings produced by the skeletonization process. The segmented sections are subsequently regularized through radial analysis and surface reconstruction to produce uniform and watertight models suitable for mesh generation in CFD software (Ansys 2024 R1). The methodology was tested on both synthetic datasets and real-world laser scans acquired in underground mine conditions. The results demonstrate that the proposed segmentation approach effectively isolates single-line drifts and crossings, ensuring continuous and smooth geometry while preserving the overall excavation topology. The developed method provides a robust preprocessing framework that bridges the gap between point cloud acquisition and numerical modelling, enabling automated transformation of raw data into CFD-ready geometric models for ventilation and safety analysis of complex underground excavation systems. Full article

Current research on the vibration characteristics of fastener clips primarily employs modal experiments combined with finite element simulations; however, limited attention has been given to the dynamic vibration behavior of clips during actual train operations. This study investigates both the quasi-static and dynamic vibration characteristics using an integrated approach of finite element simulation and dynamic testing. Based on the Vossloh W300-1 fastener system, a three-dimensional model is established. Modal and frequency response analyses, together with field test validation, reveal two significant vibration modes within 0–1000 Hz: a first-order mode at 500 Hz and a second-order mode at 560 Hz. These modes are characterized by vertical overturning of the clip arm. Dynamic testing demonstrates that the dominant frequency of the arm acceleration is strongly correlated with the second-order natural frequency, confirming that wheel–rail excitation readily triggers second-order mode resonance. The study further shows that, at train speeds of 200–350 km/h, rail corrugation with wavelengths of 99.2–173.6 mm induces high-frequency excitation at 560 Hz, resulting in resonance fatigue of the clip. As a mitigation measure, regular rail grinding is recommended to eliminate corrugation at critical wavelengths. Additionally, optimizing the clip structure to avoid resonance frequency bands is proposed. These findings elucidate the coupling mechanism between the vibration characteristics of the clip and dynamic loads, providing theoretical support for the safety evaluation of high-speed rail fastener systems and the vibration-resistant design of clips. Full article

Current object detection methods deployed in closed-circuit television (CCTV) systems experience substantial performance degradation due to domain gaps between training datasets and real-world environments. At the same time, increasing privacy concerns and stricter personal data regulations limit the reuse or distribution of source-domain data, highlighting the need for source-free learning. To address these challenges, we propose a stable and effective source-free semi-supervised domain adaptation framework based on the Mean Teacher paradigm. The method integrates three key components: (1) pseudo-label fusion, which combines predictions from weakly and strongly augmented views to generate more reliable pseudo-labels; (2) static adversarial regularization (SAR), which replaces dynamic discriminator optimization with a frozen adversarial head to provide a stable domain-invariance constraint; and (3) a time-varying exponential weighting strategy that balances the contributions of labeled and unlabeled target data throughout training. We evaluate the method on four benchmark scenarios: Cityscapes, Foggy Cityscapes, Sim10k, and a real-world CCTV dataset. The experimental results demonstrate that the proposed method improves mAP@0.5 by an average of 7.2% over existing methods and achieves a 6.8% gain in a low-label setting with only 2% labeled target data. Under challenging domain shifts such as clear-to-foggy adaptation and synthetic-to-real transfer, our method yields an average improvement of 5.4%, confirming its effectiveness and practical relevance for real-world CCTV object detection under domain shift and privacy constraints. Full article

We study the controllability of right-invariant bilinear systems on the complex and quaternionic special linear groups $\mathrm{Sl}(n,\mathbb{C})$ and $\mathrm{Sl}(n,\mathbb{H})$. The analysis relies on the Lie saturate$\mathrm{LS}(\Gamma )$, which characterizes controllability through convexity and closure properties of attainable sets, avoiding explicit Lie algebra computations. For $\mathrm{Sl}(n,\mathbb{C})$ with a strongly regular diagonal control matrix, we show that controllability is equivalent to the irreducibility of the drift matrix A, a property verified by the strong connectivity of its associated directed graph. For $\mathrm{Sl}(n,\mathbb{H})$, we derive controllability criteria based on quaternionic entries and the convexity of ${\mathbb{T}}^2$-orbits, which provide efficient sufficient conditions for general n and exact ones in the $2\times 2$ case. These results link algebraic and geometric viewpoints within a unified framework and connect to recent graph-theoretic controllability analyses for bilinear systems on Lie groups. The proposed approach yields constructive and scalable controllability tests for complex and quaternionic systems. Full article

Male fertility is important to ensure herd health and productivity. The camelid male breeding soundness examination (BSE) is strongly recommended because natural mating remains the primary breeding method due to the challenges in semen cryopreservation and artificial insemination. Guidelines for the BSE have been proposed but not adopted in practice. The investigation of male reproductive failure includes history, general health examination, examination of the genitalia, semen evaluation, and testing for contagious diseases. Difficulties in ejaculate collection and semen viscosity are challenges in camelid male fertility investigation. This review summarizes the outcomes of BSE in our practice on South American camelids (SACs) and camels. The results and discussion are presented under four main categories: congenital defects, impotentia coeundi, impotentia generandi, and male reproductive emergencies. There is a difference between camels and SACs in the incidence of various disorders. Congenital defects are common in SACs in particular cryptorchidism, testicular hypoplasia and rete testis cysts. Orchitis is more common in camels, particularly in areas where brucellosis is prevalent. Testicular degeneration occurs in all camelids and has been associated with heat stress, aging, systemic diseases and overuse of anabolic steroids. Precise diagnosis of fertility impairment may require disease testing, testicular biopsy, cytogenetics and endocrine evaluation. A significant proportion of males are referred because of reproductive emergencies, due to poor management, which results in loss of genetic potential. Implementation of regular BSE is possible in SACs but can be difficult in dromedaries because of the large variation in breed characteristics and management systems. Full article

The Reef 2050 Long-Term Sustainability Plan (Reef 2050 Plan) was crafted to protect, manage and enhance the resilience of Australia’s Great Barrier Reef (GBR). It explicitly recognises that strengthening governance is key to achieving its targeted outcomes. To date, however, the lack of evaluation of the impact of GBR governance (including many complex policies, programmes and plans) under the Reef 2050 Plan has hindered its adaption. This paper presents a first benchmark of the health of the governance system associated with the Reef 2050 Plan. A novel analytical framework was built to do this. It was populated through the gathering of multiple lines of evidence, including global theory and evaluation practice and case studies and primary data from interviews and workshops with Traditional Owners, experts across government, industry, non-government organisations and other governance systems experts. Our assessment has found the health of governance system to be emergent to maturing, yet strong by global standards. Strengths include robust global engagement, the integrative nature of the Reef 2050 Plan, crisis response systems and GBR Marine Park management. Weaknesses include the increased need for (i) power sharing with Traditional Owners; (ii) rebuilding governmental trust with the farming and fishing sectors; (iii) more contemporary spatial planning for GBR and catchment resilience; and (iv) greater subsidiarity to deliver government programmes. In conclusions, we strongly recommend that regular benchmarking and informed refinement of Reef 2050 Plan governance arrangements would mature the system toward better outcomes. Full article

This paper primarily investigates the solutions to the system of equations $A_{1}X{B}_1=C_1$ and $A_{2}X{B}_2=C_2$. This system generalizes the classical equation $AXB=C$, as well as the system of equations $AX=B$ and $XC=D$, and finds broad applications in control theory, signal processing, networking, optimization, and other related fields. Various methods for solving this system are introduced, including the generalized inverse method, the $\mathrm{vec}$-operator method, matrix decomposition techniques, Cramer’s rule, and iterative algorithms. Based on these approaches, the paper discusses general solutions, symmetric solutions, Hermitian solutions, and other special types of solutions over different algebraic structures, such as number fields, the real field, the complex field, the quaternion division ring, principal ideal domains, regular rings, strongly *-reducible rings, and operators on Banach spaces. In addition, matrix systems related to the system $A_{1}X{B}_1=C_1$ and $A_{2}X{B}_2=C_2$ are also explored. Full article

The development of deep coalbed methane (buried depth > 2000 m) in the Yan’an block of Ordos Basin is limited by low permeability, the pore structure of the coal reservoir, and the gas–water occurrence relationship. It is urgent to clarify the key control mechanism of pore structure on gas migration. In this study, based on high-pressure mercury intrusion (pore size > 50 nm), low-temperature N₂/CO₂ adsorption (0.38–50 nm), low-field nuclear magnetic resonance technology, fractal theory and Pearson correlation coefficient analysis, quantitative characterization of multi-scale pore–fluid system was carried out. The results show that the multi-scale pore network in the study area jointly regulates the occurrence and migration process of deep coalbed methane in Yan’an through the ternary hierarchical gas control mechanism of ‘micropore adsorption dominant, mesopore diffusion connection and macroporous seepage bottleneck’. The fractal dimensions of micropores and seepage are between 2.17–2.29 and 2.46–2.58, respectively. The shape of micropores is relatively regular, the complexity of micropore structure is low, and the confined space is mainly slit-like or ink bottle-like. The pore-throat network structure is relatively homogeneous, the difference in pore throat size is reduced, and the seepage pore shape is simple. The bimodal structure of low-field nuclear magnetic resonance shows that the bound fluid is related to the development of micropores, and the fluid mobility mainly depends on the seepage pores. Pearson’s correlation coefficient showed that the specific surface area of micropores was strongly positively correlated with methane adsorption capacity, and the nanoscale pore-size dominated gas occurrence through van der Waals force physical adsorption. The specific surface area of mesopores is significantly positively correlated with the tortuosity. The roughness and branch structure of the inner surface of the channel lead to the extension of the migration path and the inhibition of methane diffusion efficiency. Seepage porosity is linearly correlated with gas permeability, and the scale of connected seepage pores dominates the seepage capacity of reservoirs. This study reveals the pore structure and ternary grading synergistic gas control mechanism of deep coal reservoirs in the Yan’an Block, which provides a theoretical basis for the development of deep coalbed methane. Full article

Offshore cranes equipped with active motion compensation (AMC) systems play a vital role in marine engineering tasks such as offshore wind turbine maintenance, subsea operations, and dynamic load positioning under wave-induced disturbances. These systems rely on complex hydraulic actuators whose strongly nonlinear dynamics—often described by differential-algebraic equations (DAEs)—impose significant computational burdens, particularly in real-time applications like hardware-in-the-loop (HIL) simulation, digital twins, and model predictive control. To address this bottleneck, we propose a neural network-based surrogate model that approximates the actuator dynamics with high accuracy and low computational cost. By approximately reducing the original DAE model, we obtain a lower-dimensional ordinary differential equations (ODEs) representation, which serves as the foundation for training. The surrogate model includes three hidden layers, demonstrating strong fitting capabilities for the highly nonlinear characteristics of hydraulic systems. Bayesian regularization is adopted to train the surrogate model, effectively preventing overfitting. Simulation experiments verify that the surrogate model reduces the solving time by 95.33%, and the absolute pressure errors for chambers $p_1$ and $p_2$ are controlled within 0.1001 MPa and 0.0093 MPa, respectively. This efficient and scalable surrogate modeling framework possesses significant potential for integrating high-fidelity hydraulic actuator models into real-time digital and control systems for offshore applications. Full article

Background and Objectives: In Germany, access to medical care is often hindered by long wait times for specialist appointments and emergency department care. Inappropriate utilization of emergency services further exacerbates delays for truly urgent cases. To evaluate the utilization of the statutory ophthalmic emergency service in Freiburg and identify patient- and system-level factors contributing to inappropriate use. Materials and Methods: A paper-based, anonymous questionnaire was distributed to patients attending the ophthalmologic emergency practice (Notfallpraxis) of the Association of Statutory Health Insurance Physicians (Kassenärztliche Vereinigung), which is located within the premises of the Eye Center of the University Hospital Freiburg, Germany, at selected periods between July and September 2020, alongside a short physician assessment. Standardized instruments were used to assess symptom severity, urgency perception, and healthcare-seeking behavior. Statistical analyses were performed using R and Excel. Results: A total of 157 questionnaires were included (response rate: 63%). Most visits occurred on weekends (47%) and before 10 p.m. (83%). While 68% of patients believed their symptoms required same-day treatment, physicians assessed only 30% of cases as clinically urgent. A total of 60% of patients did not attempt to contact an outpatient ophthalmologist beforehand, and only 38% reported having a regular ophthalmologist. Patients’ perceived urgency was significantly associated with symptom severity and older age, whereas physician-assessed urgency was strongly linked to symptom duration. Conclusions: A substantial proportion of ophthalmic emergency visits in Freiburg are for non-urgent conditions. These findings underscore the need for improved coordination with outpatient care providers, better patient education, and structural reforms to reduce inappropriate utilization and ensure timely access for truly urgent cases. Full article

The optimization of computational algorithms is one of the main problems of computational mathematics. This optimization is well demonstrated by the example of the theory of quadrature and cubature formulas. It is known that the numerical integration of definite integrals is of great importance in basic and applied sciences. In this paper we consider the optimization problem of weighted quadrature formulas with derivatives in Sobolev space. Using the extremal function, the square of the norm of the error functional of the considered quadrature formula is calculated. Then, minimizing this norm by coefficients, we obtain a system to find the optimal coefficients of this quadrature formula. The uniqueness of solutions of this system is proved, and an algorithm for solving this system is given. The proposed algorithm is used to obtain the optimal coefficients of the derivative weight quadrature formulas. It should be noted that the optimal weighted quadrature formulas constructed in this work are optimal for the approximate calculation of regular, singular, fractional and strongly oscillating integrals. The constructed optimal quadrature formulas are applied to the approximate solution of linear Fredholm integral equations of the second kind. Finally, the numerical results are compared with the known results of other authors. Full article

This paper concerns the analysis of the impact of nodal powers on currents flowing in the power system (PS). Two problems are considered here, i.e., Problem I—identifying the branches of the PS on which currents have magnitudes that strongly change with changes in nodal powers, characterized by magnitudes and arguments, and identifying nodes at which these powers exist, and Problem C—PS clustering from the point of view of the relationships between branch current magnitudes (BCMs) and nodal power magnitudes (nodal apparent powers—NAPs) or nodal power arguments (NPAs). The solution to Problem I may be useful for the modernization of the PS as well as in the practice of dispatchers. The solution to Problem C may be useful in system analyses. The analysis of the literature shows that the existing papers only touch on the earlier-formulated problems to a modest extent. In fact, those problems are not solved. The paper fills this gap by presenting methods for solving the given problems. Both considered problems are solved using data mining. The investigation of correlational relationships (CRs) between BCMs and NAPs as well as CRs between BCMs and NPAs is used. Any such strong CR indicates large changes in BCM with changes in NAP or NPA remaining in the considered CR. Nodes, which through NAPs are in CRs with BCM for a selected branch, are a cluster associated with this branch. The paper also considers clusters encompassing branches, for each of which BCMs are in CRs with the NAP of a given node. Similarly, when searching for clusters encompassing nodes, or clusters encompassing branches, in the aforementioned CRs, one considers NPAs instead of NAPs. The paper proposes methods for solving Problem I and Problem C, which allow (i) relatively simple detection of regularities in the PS with the provision of their statistical evaluation, which would be difficult or impossible in the case of other methods, and (ii) solving the indicated problems based only on measurement data, and do not require (i) performing flow calculations and (ii) large computational effort. The paper presents the properties of the methods on the examples of the IEEE 14-Bus Test System and IEEE 30-Bus Test System. Full article

Background: University students’ awareness of oral health plays an important role in lifelong health promotion. However, the factors influencing this awareness among Japanese university students are not fully understood. This study aimed to comprehensively examine and analyze Japanese university students’ perceptions of their oral health status, self-reported oral symptoms, and oral health-related behaviors. Methods: A cross-sectional survey was conducted among undergraduate students using an anonymous online questionnaire to collect information on their basic attributes and self-reported items related to oral health status, oral health behavior, and lifestyle habits. The chi-square test and logistic regression analysis were used to examine factors associated with oral health status. Results: A total of 5482 students participated in this study. Overall, 75.9% of the respondents reported that their oral health was good. Factors significantly associated with good oral health were the absence of dental caries and periodontal disease, tooth brushing at least twice a day, regular dental visits, conscious toothpaste selection, and lack of concern about dental care costs and pain during treatment. Conclusions: Oral diseases and symptoms, oral health behaviors, and psychosocial factors were strongly associated with university students’ awareness of their oral health. Since oral health is closely related to systemic health, it is essential to promote proper oral hygiene practices at an early age. Therefore, providing oral health education for university students may contribute to lifelong health promotion and prevention of systemic diseases. Full article

Urban lake degradation caused by intensive urbanization necessitates systematic solutions, with water connectivity being a crucial ecological restoration strategy. This study evaluates the two-year effects (2020–2022) of connectivity interventions on seven lakes in Yangshuo, Guilin, classified by connectivity: multi-channel (Mc), single-channel (Sc), and non-connected (Nc). Regular monitoring of the physicochemical parameters and microbial communities revealed significant patterns: multi-channel connected lakes exhibited superior water quality improvement, with trophic state downgrading (weak eutrophic → mesotrophic), but the water quality of Sc-BQ was deteriorating. Seasonal variations showed wet season peaks in pH, DO, COD_Mn, and Chl-a, versus dry season elevations in NH₃-N, NO₃-N, TN, and TP. Correlation analysis identified organic matter as the primary driver of eutrophication, with TN strongly linked to NH₃-N, indicating persistent domestic sewage contamination. Microbial community restructuring was accompanied by changes in water quality, and the abundance and diversity of OTUs decreased after restoration. Notably, Limnohabitans dominated Mc lakes (31.82–35.1%), while Pleurocapsa prevailed (37.85%) in Nc-LH under weak eutrophic conditions. These findings demonstrate that multi-channel connectivity effectively enhances hydrodynamic conditions and pollutant dispersion, whereas inadequate connectivity exacerbates nutrient accumulation. The study provides critical empirical evidence for optimizing urban lake management, emphasizing the necessity of multi-dimensional connectivity designs and targeted control of untreated sewage inputs in water system rehabilitation projects. Full article

High-purity distillation columns typically give rise to multi-variable, strongly coupled nonlinear systems with substantial time delay and significant inertia. The control performance of high-purity distillation columns crucially influences the purity of the final product. Taking into account the process of a high-purity distillation column, this article puts forward a dual-loop modified active disturbance rejection control (MADRC) scheme to improve the control of product purity. During the stable operation of the distillation process, the structures of two control loops are, respectively, approximated by two linear transfer function models via open-loop experiments. Subsequently, the compensation part of the MADRC scheme is designed, respectively, for each approximate model. Furthermore, this paper employs singular perturbation theory to prove the stability of MADRC. The performance of the dual-loop MADRC scheme (MADRC) is compared with that of a proportional–integral–derivative (PID) control scheme, a cascade PID control scheme (CPID), and a regular ADRC scheme (ADRC). The simulations demonstrate that the dual-loop MADRC scheme is capable of efficiently tracking the reference value and exhibits optimal disturbance rejection capabilities. Additionally, the superiority of the dual-loop MADRC scheme is validated through Monte Carlo trials. Full article