Water inrush is a major hazard for mining and excavation in deep coal seams or rock masses. It can be attributed to the coalescence of rock fractures in rock mass due to the interaction of fractures, hydraulic flow and stress field. One of the key technical challenges is to understand the course and mechanism of fluid flows in rock joint networks and fracture propagation and hence to take measures to prevent the formation of water inrush channels caused by possible rock fracturing. Several case observations of fluid flowing in rock joint networks and coupled fracture propagation in underground coal roadways are shown in this paper. A number of numerical simulations were done using the recently developed flow coupling function in FRACOD which simulates explicitly the fracture initiation and propagation process. The study has demonstrated that the shortest path between the inlet and outlet in joint networks will become a larger fluid flow channel and those fractures nearest to the water source and the working faces become the main channel of water inrush. The fractures deeper into the rib are mostly caused by shearing, and slipping fractures coalesce with the joint, which connects the water source and eventually forming a water inrush channel.
The purpose of this study is to investigate the current status of clinical target volume (CTV) delineation for primary site of nasopharyngeal cancer (NPC) among five large tertiary cancer centers in China.The simulation CT and MR images of a patient with T3N2M0 NPC were sent to the centers participating. Fourteen experienced physicians contoured the targets independently, and the outlined structures were compared. The consistency and differences among these 14 CTVs are discussed.Two different CTV designs were used in the centers. "One-CTV" design defines one CTV with a dose of 60 Gy, whereas "two-CTV" design has a high-risk CTV with dose of 60 Gy and a medium risk CTV with dose of 54 Gy. We found that the coverage of prophylactic area is very consistent between these two designs. The variances on the coverage of some sites were also significant among physicians, including covering cavernous sinus at un-involved side, posterior space of styloid process, and caudal border on posterior pharyngeal wall.Standardization is the main requirement for personalization of care; our study shows that among the 14 physicians in the five centers the coverage of prophylactic areas is in excellent agreement. Two distinct strategies on CTV design are currently being used, and multiple controversies were found, suggesting further optimization of CTV for primary site of NPC is needed.
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Assessing the presence of potentially malignant lymph nodes aids in estimating cancer progression, and identifying surrounding benign lymph nodes can assist in determining potential metastatic pathways for cancer. For quantitative analysis, automatic segmentation of lymph nodes is crucial. However, due to the labor-intensive and time-consuming manual annotation process required for a large number of lymph nodes, it is more practical to annotate only a subset of the lymph node instances to reduce annotation costs. In this study, we propose a pre-trained Dual-Branch network with Dynamically Mixed Pseudo label (DBDMP) to learn from partial instance annotations for lymph nodes segmentation. To obtain reliable pseudo labels for lymph nodes that are not annotated, we employ a dual-decoder network to generate different outputs that are then dynamically mixed. We integrate the original weak partial annotations with the mixed pseudo labels to supervise the network. To further leverage the extensive amount of unannotated voxels, we apply a self-supervised pre-training strategy to enhance the model’s feature extraction capability. Experiments on the mediastinal Lymph Node Quantification (LNQ) dataset demonstrate that our method, compared to directly learning from partial instance annotations, significantly improves the Dice Similarity Coefficient (DSC) from 11.04% to 54.10% and reduces the Average Symmetric Surface Distance (ASSD) from 20.83 mm to 8.72 mm. The code is available at <a href='https://github.com/WltyBY/LNQ2023_training_code'>https://github.com/WltyBY/LNQ2023_training_code</a>
Conventional borehole pressure relief can meet the requirements for preventing rock bursts, but it can also easily destroy the roadway, resulting in system support failure. Taking coal-like samples with boreholes as the research object, the pressure relief effects of the same-diameter boreholes and variable-diameter boreholes are compared and analyzed by a uniaxial compression test. The joint pressure relief mechanism of the variable-diameter drilling hole is discussed. The experimental results show that the stress–strain curve of variable-diameter drilling sample occurred the phenomenon of pre-peak stress drop and post-peak stress plateau, which indicates that the variable-diameter drilling hole can enhance the plastic characteristics of coal-like samples. The borehole size dramatically influences the variation of various pressure relief indexes. The evolution law of AE counting the pre-peak and post-peak of borehole samples verified the abovementioned law. Variable-diameter drilling can enhance the plasticity of samples, weaken the brittleness and reduce the impact tendency. Under the maximum size of the variable-diameter drilling hole and the same-diameter drilling hole is same, the pressure relief effect is more significant. The results obtained in this paper can provide a new theoretical basis and technical guidance for borehole pressure relief and roadway support.
Nasopharyngeal Carcinoma (NPC) is a leading form of Head-and-Neck (HAN) cancer in the Arctic, China, Southeast Asia, and the Middle East/North Africa. Accurate segmentation of Organs-at-Risk (OAR) from Computed Tomography (CT) images with uncertainty information is critical for effective planning of radiation therapy for NPC treatment. Despite the stateof-the-art performance achieved by Convolutional Neural Networks (CNNs) for automatic segmentation of OARs, existing methods do not provide uncertainty estimation of the segmentation results for treatment planning, and their accuracy is still limited by several factors, including the low contrast of soft tissues in CT, highly imbalanced sizes of OARs and large inter-slice spacing. To address these problems, we propose a novel framework for accurate OAR segmentation with reliable uncertainty estimation. First, we propose a Segmental Linear Function (SLF) to transform the intensity of CT images to make multiple organs more distinguishable than existing methods based on a simple window width/level that often gives a better visibility of one organ while hiding the others. Second, to deal with the large inter-slice spacing, we introduce a novel 2.5D network (named as 3D-SepNet) specially designed for dealing with clinic HAN CT scans with anisotropic spacing. Thirdly, existing hardness-aware loss function often deal with class-level hardness, but our proposed attention to hard voxels (ATH) uses a voxel-level hardness strategy, which is more suitable to dealing with some hard regions despite that its corresponding class may be easy. Our code is now available at https://github.com/HiLab-git/SepNet.
The instability of hard and brittle rock often leads to disastrous consequences in underground engineering. Under various surrounding rock pressure conditions, in situ stress induces corresponding deformation and damage to the floor post-mining. Therefore, it is crucial to examine the effects of mining under different confining pressures on rock disturbance, damage characteristics, and their distribution. Consequently, triaxial loading experiments under varying intermediate principal stress conditions were conducted on red sandstone specimens, using an acoustic emission monitoring system to track energy changes during rock damage and failure. This approach aids in studying crack generation, propagation, and fracture damage evolution. The results indicate that rock deformation results in axial compression and dilatancy, aligned with the direction of minimum and intermediate principal stresses. Ductility in rock failure becomes more pronounced with increased stress, primarily manifesting as shear failure. Internal cracks in the specimen lead to stress concentration and marked plastic deformation under compression, yet do not result in macroscopic surface cracks. The fracture angle θ of specimens post-failure generally exceeds 45° and varies with stress changes; at consistent burial depths, the angle of the sandstone failure surface increases with intermediate principal stress. This paper preliminarily establishes the informational linkage between rock failure and energy release, analyzing the rock samples over time and space. This research offers insights for analyzing and mitigating sudden rock instability.
BackgroundThe prognostic effects of different treatment modalities on patients with hypopharyngeal squamous cell carcinoma (HPSCC) remain unclear.MethodsHPSCC patients diagnosed and treated at either West China Hospital or Sichuan Cancer Hospital between January 1, 2009, and December 31, 2019, were enrolled in this retrospective, real-world study. Survival rates were presented using Kaplan–Meier curves and compared using log-rank tests. Univariable and multivariable Cox proportional hazards regression models were used to identify the predictors of overall survival (OS). Subgroup analyses were conducted for patients with advanced-stage HPSCC (stages III and IV and category T4).ResultsA total of 527 patients with HPSCC were included. Patients receiving SRC (surgery, radiotherapy [RT], and chemotherapy) showed the best OS (p < 0.0001). In comparison with RT alone, both surgery alone (all cases: hazard ratio [HR] = 0.39, p = 0.0018; stage IV cases: HR = 0.38, p = 0.0085) and surgery-based multimodality treatment (SBMT; all cases: HR = 0.27, p < 0.0001; stage IV cases: HR = 0.30, p = 0.00025) showed prognostic benefits, while SBMT also showed survival priority over chemoradiotherapy (CRT; all cases: HR = 0.52, p < 0.0001; stage IV cases: HR = 0.59, p = 0.0033). Moreover, patients who underwent surgery alone had comparable OS to those who underwent SBMT (all patients: p = 0.13; stage IV cases: p = 0.34), while CRT yielded similar prognostic outcomes as RT alone (all patients: p = 0.054; stage IV cases: p = 0.11).ConclusionsSurgery alone was comparable to SBMT and superior to RT/CRT in terms of OS in patients with HPSCC. We suggest that surgery should be encouraged for the treatment of HPSCC, even in patients with advanced-stage disease.
Under the long-term influence of overburden load and water infiltration, coal undergoes creep damage, and the disturbance caused by mining activities can lead to sudden instability, triggering geological disasters such as mine flooding. Therefore, this study prepared four types of coal samples with different saturations under creep damage conditions and conventional coal samples. A comparative study was conducted using uniaxial compression tests to examine the deterioration characteristics of physical and mechanical parameters, failure modes, and energy evolution patterns in these two types of coal samples. Additionally, a microscopic deterioration model of coal samples under the combined influence of water and creep damage was constructed to elucidate the mechanism of creep damage on the deterioration of mechanical properties in water-containing coal samples. The research findings indicate that coal samples affected by creep damage and conventional coal samples exhibit significant consistency in mechanical parameters and energy evolution patterns. Specifically, an increase in saturation is positively correlated with peak stress, elastic modulus, and dissipated energy. Conversely, peak strain, total input energy, and elastic strain energy are negatively correlated with rising saturation levels. Under the same saturation conditions, the change in mechanical parameters and energy characteristics is more pronounced in creep-damaged coal samples. Furthermore, the stress-strain curves of both coal sample types exhibit prolonged compaction stages, shortened elastic stages, and more significant yield stages. Under equivalent saturation levels, the stress-strain trends in creep-damaged coal samples show more substantial variations. Upon loading and failure, the conventional coal sample transitions from single inclined plane shear failure to tension-shear mixed failure as the saturation increases. Conversely, the creep-damaged coal sample shifts from "X"-type conjugate shear failure and tension-shear mixed failure to tension failure, signifying a tendency toward more complex failure modes. In cases where the coal sample has a water saturation of 41%, the deterioration of its mechanical parameters is primarily attributed to creep damage. However, when the water saturation reaches 41–100%, water plays a dominant role in the deterioration of the coal sample's mechanical parameters. After experiencing creep damage, the internal micro-cracks of the coal sample are extensively developed, which is also the primary factor contributing to the deterioration of the coal sample's mechanical properties and an increased proportion of dissipated energy.
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