Identification Methods of the Deformation Memory Effect in the Stress Region above Crack Initiation Threshold

AbstractDeformation memory effect (DME) is one of the rock memory effects. One important application of the DME is to determine the in situ stress state. Compared to the traditional in situ stress measurements, the methods based on the DME are commercial and permit large number of measurements. Application of DME needs enough reliable identification methods. However, the existing methods sometimes are indistinct and the amount is insufficient. combined with three traditional methods including tangential modulus method, deformation rate analysis (DRA), acoustic emission method, two new potential methods were explored in the stress region above crack initiation threshold. One is based on the fractal dimension, called FD method. Another one is to take advantage of the lateral strain in the DRA method and the FD method, instead of using the axial strain. Based on the contact bond model in PFC2D, numerical model for granite sample was developed and cyclic uniaxial compressions were performed on it. Both the existing methods and new methods were used to detect the DME. The results demonstrate that the FD method is effective and reliable, result by DRA method with lateral strain is better than that with the axial strain, the tangential modulus method is not so distinct as other methods

Task Decomposition and Synchronization for Semantic Biomedical Image Segmentation

Semantic segmentation is essentially important to biomedical image analysis. Many recent works mainly focus on integrating the Fully Convolutional Network (FCN) architecture with sophisticated convolution implementation and deep supervision. In this paper, we propose to decompose the single segmentation task into three subsequent sub-tasks, including (1) pixel-wise image segmentation, (2) prediction of the class labels of the objects within the image, and (3) classification of the scene the image belonging to. While these three sub-tasks are trained to optimize their individual loss functions of different perceptual levels, we propose to let them interact by the task-task context ensemble. Moreover, we propose a novel sync-regularization to penalize the deviation between the outputs of the pixel-wise segmentation and the class prediction tasks. These effective regularizations help FCN utilize context information comprehensively and attain accurate semantic segmentation, even though the number of the images for training may be limited in many biomedical applications. We have successfully applied our framework to three diverse 2D/3D medical image datasets, including Robotic Scene Segmentation Challenge 18 (ROBOT18), Brain Tumor Segmentation Challenge 18 (BRATS18), and Retinal Fundus Glaucoma Challenge (REFUGE18). We have achieved top-tier performance in all three challenges.Comment: IEEE Transactions on Medical Imagin

Correlation between magnetic resonance images of peritumor margin enhancement and prognosis in hepatocellular carcinoma after drug-eluting bead transcatheter arterial chemoembolization

PurposeThe aim of this study is to investigate the morphological characteristics and clinical significance of magnetic resonance (MR) images of peritumor margin enhancement in hepatocellular carcinoma (HCC) after drug-eluting bead transcatheter arterial chemoembolization (DEB-TACE).MethodsFrom January 2017 to December 2020, a total of 162 patients who received a diagnosis of HCC were included in our study. We began the follow-up with magnetic resonance imaging (MRI) for complete response assessment, and peritumor margin enhancements were classified as sharp and rough types according to morphology. During the follow-up, data such as progression or remission of the two enhancement modalities, morphological changes in terms of margin enhancements observed in MR images, and alpha-fetoprotein (AFP) levels were recorded.ResultsIn the follow-up period of 36 months, 70 and 92 patients with sharp- and rough-type peritumor margins, respectively, were observed. At the end of the follow-up, patients with sharp-type margins had lower AFP levels and longer progression-free survival than those with rough-type margins (P < 0.05). Furthermore, the sharp-type margin was thinner than the rough-type margin (all P < 0.05). Moreover, the sharp-type group had a high incidence of tumors with a diameter of < 5 cm, whereas the rough-type group had a high incidence of tumors with a diameter of ≥ 5 cm. Continuous enhancements of peritumor margins in MRI were greater in the sharp-type group than in the rough-type group. Most of the patients with a sharp-type margin achieved disease remission (94.3%, P < 0.05), whereas most of those with a rough-type margin experienced disease progression (84.8%, P < 0.05).ConclusionsPatients with HCC with a sharp-type margin enhancement on MRI after DEB-TACE mostly demonstrated benign lesions with a good prognosis, whereas those with a rough-type margin mostly demonstrated malignant growth

Stability analysis of concrete gravity dam on complicated foundation with multiple slide planes

A key problem in gravity dam design is providing enough stability to prevent slide, and the difficulty increases if there are several weak structural planes in the dam foundation. Overload and material weakening were taken into account, and a finite difference strength reserve method with partial safety factors based on the reliability method was developed and used to study the anti-slide stability of a concrete gravity dam on a complicated foundation with multiple slide planes. Possible slide paths were obtained, and the stability of the foundation with possible failure planes was evaluated through analysis of the stress distribution characteristics. The results reveal the mechanism and process of sliding due to weak structural planes and their deformations, and provide a reference for anti-slide stability analysis of gravity dams in complicated geological conditions

Effect of laparoscopic surgical procedures on serum anti-Mullerian hormone level

Objective To investigate the effect of 3 laparoscopic surgical procedures (hysterectomy, oophorectomy and fallectomy) on anti-Mullerian hormone (AMH) level. Methods A total of 162 women who were treated with laparoscopic surgical procedures (56 cases of hysterectomy, 52 cases of oophorectomy and 54 cases of fallectomy) in our department from November 2019 to February 2021 were enrolled in this study. The AMH level of each patient was compared preoperatively, and 1, 3 and 6 months postoperatively. The changes in AMH for the same type, different surgical procedures, were also compared. Results No statistical difference was observed in preoperative serum AMH level among the 3 groups of patients (P>0.05), and the level was significantly decreased in the ovarian and hysterectomy groups than the fallopian tube group in 1 month postoperatively (P=0.04). At 3 and 6 months postoperatively, there was no difference in serum AMH level in the 3 groups (P=0.1, P=0.33), and △AMH level was decreased gradually. For the same type, different surgical procedures, when compared with subtotal hysterectomy, serum AMH level was decreased more significantly in patients with total hysterectomy at 1, 3 and 6 months postoperatively than preoperative level (P=0.016, P=0.021, P=0.021), and the decrease in AMH was more obviously in bilateral than in unilateral oophorectomy. Conclusion All these 3 types of common laparoscopic gynecological surgeries affect ovarian function, with ovarian surgery most significant, followed by hysterectomy and then salpingo-oophorectomy. Total uterine resection has more obvious effect on postoperative decline in ovarian reserve than sub-total uterine resection, and bilateral salpingo-oophorectomy than unilateral salpingo-oophorectomy, especially in 1 month postoperatively, while no such effect is observed in unilateral salpingo-oophorectomy

Influence of the Cyclic Loading Path on Rock Deformation Memory Effect

Deformation rate analysis utilizes deformation memory effect (DME) that is one of the fundamental properties of rock, to estimate in situ stress underground. It could be influenced by the stress history which has been subjected to in the past. To understand the influence under the cyclic loading path, in the experimental study, different stress levels were applied on sandstone samples and two types of granite samples. In the theoretical investigation, the sliding friction model consisting of multiple microstructure surfaces is considered in this paper. Both experiments and the theoretical model show that when the number of cyclic loading times keeps increasing, (1) the stress read at the DRA inflection is getting closer to the previously cyclic stress; (2) the angle at the DRA inflection becomes sharper, which gives clearer inflection point; and (3) the strain differential amplitude in the DRA curve gradually decreases and then toward a stable value. An upper limit exists for influence, indicating that the best cyclic loading times occur when the pulse amplitude of the strain differential stops changing. It is confirmed that the multiple cyclic loading method provides a better outcome for experiment using artificial preload when DME is utilized for stress reconstruction. Without other factors disturbing, the memory information of the in situ stress would hardly lose under the history of cyclic loading

Experimental and Numerical Study on the Failure Characteristics of Brittle Solids with a Circular Hole and Internal Cracks

A stress analysis of a circular hole is one of the classical problems in mechanics. Internal cracks are inherent properties of materials, and they are mostly three-dimensional in form. However, studies on hole problems with three-dimensional internal cracks are still lacking. In this paper, internal cracks were generated in brittle materials containing circular holes based on 3D internal laser-engraved crack technology. Then, uniaxial compression tests were performed. The experimental results were compared with the existing literature, and theoretical and numerical simulation studies were carried out. The results show that: (1) The main crack shapes are the primary cracks and remote cracks. (2) The dynamic fracture characteristics existed in the formation of primary cracks and the surface of remote cracks. The tips of primary cracks were arc-shaped, and the surfaces of the remote cracks were curved. Remote cracks were tangential to the orifice where type III spear-like characteristics appeared. (3) The stress birefringence technology can be combined with 3D internal laser-engraved crack technology for internal crack stress information monitoring, the moire around the orifice was “flamboyant”, and the moire at the tip of the prefabricated crack was “petallike”. (4) The existence of internal cracks reduced the cracking and breaking load of the specimen, and compared with the intact orifice specimen, the upper primary crack, the lower primary crack, the remote crack and the failure load were reduced by 41.2%, 31.7%, 15.9%, and 32.3%, respectively. (5) The results of qualitative stress analysis of the orifice specimen were consistent with the initiation law of primary cracks and remote cracks. The K distribution based on M integral and the numerical simulation of crack propagation process based on the maximum tensile stress criterion were consistent with the law of primary crack growth. Compared with the current mainstream method of transparent rock research, 3D internal laser-engraved crack technology has certain advantages in terms of brittleness, crack authenticity, stress field visualization, and fracture characteristics, and the result will provide experimental and theoretical references for research on three-dimensional problems and internal cracks in fracture mechanics

Simulating the chemical-mechanical-damage coupling problems of cement-based materials using an improved smoothed particle hydrodynamics method

The applications of Smoothed Particle Hydrodynamics (SPH) into the chemical - mechanical - damage coupling problems of cement - based materials have been rarely investigated. Based on this background, the diffusion equations of chemical ion concentration in SPH form are derived. Traditional kernel function in SPH is improved by introducing the ion concentration damage coefficient Dc. Firstly, the chemical corrosion processes of a semicircular corrosion pit are simulated, and the rationality is verified by comparing with previous experimental results. Then the effects of different bedding direction, random aggregates and their anisotropy degrees on the chemical corrosion processes are discussed. Finally, a chemical-stress-damage coupling model is established to simulate the crack propagation processes. The research results can provide some references for the comprehensive understandings of the chemical-stress-damage coupling laws, as well as the applications of SPH method into the chemical-stress-damage coupling simulations of cement-based materials