Antarctic Snow Failure Mechanics: Analysis, Simulations, and Applications.

Snow failure is the process by which the stability of snow or snow-covered slopes is destroyed, resulting in the collapse or release of snow. Heavy snowfall, low temperatures, and volatile weather typically cause consequences in Antarctica, which can occur at different scales, from small, localized collapses to massive avalanches, and result in significant risk to human activities and infrastructures. Understanding snow damage is critical to assessing potential hazards associated with snow-covered terrain and implementing effective risk mitigation strategies. This review discusses the theoretical models and numerical simulation methods commonly used in Antarctic snow failure research. We focus on the various theoretical models proposed in the literature, including the fiber bundle model (FBM), discrete element model (DEM), cellular automata (CA) model, and continuous cavity-expansion penetration (CCEP) model. In addition, we overview some methods to acquire the three-dimensional solid models and the related advantages and disadvantages. Then, we discuss some critical numerical techniques used to simulate the snow failure process, such as the finite element method (FEM) and three-dimensional (3D) material point method (MPM), highlighting their features in capturing the complex behavior of snow failure. Eventually, different case studies and the experimental validation of these models and simulation methods in the context of Antarctic snow failure are presented, as well as the application of snow failure research to facility construction. This review provides a comprehensive analysis of snow properties, essential numerical simulation methods, and related applications to enhance our understanding of Antarctic snow failure, which offer valuable resources for designing and managing potential infrastructure in Antarctica.

YOLOX-DG robotic detection systems for large-scale underwater concrete structures.

Large-scale complex underwater concrete structures have structural damage and the traditional damage detection method mostly uses manual identification, which is inaccurate and inefficient. Therefore, robotic detection systems have been proposed to replace manual identification for underwater concrete structures in ocean engineering. However, the highly corrosive and disruptive environment of the ocean poses great difficulties for the application. Here, we develop a manta ray-inspired underwater robot with well controllability to establish the damage datasets of underwater concrete structures, proposing the YOLOX-DG algorithm to improve the damage detection accuracy, and integrating the model into the robotic detection systems for underwater concrete damages. Eventually, the system is used for ocean testing in real applications (i.e., underwater marine harbors around the East China Sea), and satisfactory detection performance is obtained. The reported manta ray-inspired robotic detection system can be used to accurately monitor and analyze the underwater regions.

Enhanced interfacial boiling of impacting droplets upon vibratory surfaces.

HYPOTHESIS: Despite the flourishing studies of droplet interfacial boiling, the boiling upon vibratory surfaces, which may cause vigorous liquid-vapor-solid interactions, has rarely been investigated. Enhanced boiling normally can be gained from rapid removal of vapor and disturbance of liquid-vapor interface. We hypothesize that the vibratory surfaces enhance both effects with new intriguing phenomena and thus, attain an enhanced boiling heat transfer. EXPERIMENTS: We experimentally investigated the impacting fluid dynamics and coupled heat transfer patterns of multiple droplets and a single droplet impinging on still and vibratory surfaces of various materials and different wettability. FINDINGS: The boiling under vibratory surfaces with increased vibration velocity amplitude and enhanced wettability can be enhanced by 80% in heat transfer coefficient and Nusselt number, which is attributed to several reasons: shortened bubble lifespan, thinner and smaller bubbles, and enhanced disturbances in liquid-vapor interfaces. The vibration also delays the Leidenfrost point when the droplet impacts a descending surface, which shows that the droplet impact moment (vibration phase angle) is particularly crucial. The descending surface releases the generated vapor actively and facilitates liquid-solid contact, thereby delaying the Leidenfrost. From fundamentals to application, this article strengthens our understanding of vibrated interfacial boiling in scenarios closer to multiple natural processes and practical industries.

[Rapid evaluation of the early pathogen of severe Chlamydophila psittaci pneumonia by diagnostic bronchoscopy].

OBJECTIVE: To explore the rapid evaluation of the early pathogen of severe Chlamydophila psittaci pneumonia by bedside diagnostic bronchoscopy, so as to start effective anti-infection treatment before the results of macrogenome next generation sequencing (mNGS) test. METHODS: The clinical data of three patients with severe Chlamydophila psittaci pneumonia who were successfully treated in the First Affiliated Hospital of Xinjiang Medical University, the First People's Hospital of Aksu District, and the First Division Hospital of Xinjiang Production and Construction Corps from October 2020 to June 2021 were retrospectively analyzed, including the rapid assessment of early pathogens by bedside diagnostic bronchoscopy and the use of antibiotics to start anti-infection treatment. These patients were successfully treated. RESULTS: The three patients were male, aged 63, 45 and 58 years old, respectively. Before the onset of the penumonia, they had a clear medical history of bird exposure. The clinical manifestations mainly included fever, dry cough, shortness of breath and dyspnea. One case had abdominal pain and lethargy. The results of laboratory examination indicated that the peripheral blood white blood cell count (WBC) of two patients were high [(10.2-11.9)×109/L], the percentage of neutrophils increased (85.2%-94.6%) and the percentage of lymphocytes decreased (3.2%-7.7%) in all 3 patients after admission to hospital and entering into intensive care unit (ICU). The procalcitonin (PCT) of 3 patients increased after admission, and still increased when entering ICU (0.3-4.8 ng/L), so did C-reactive protein (CRP, 58.0-162.0 mg/L) and erythrocyte sedimentation rate (ESR, 36.0-90.0 mm/1 h). After admission, serum alanine transaminase (ALT) increased in 2 cases (136.7 U/L, 220.5 U/L), so did aspartate transaminase (AST) in 2 cases (249.6 U/L, 164.2 U/L). ALT (162.2-267.9 U/L) and AST (189.8-223.2 U/L) increased in 3 patients when they entered ICU. The level of serum creatinine (SCr) of 3 patients were normal after admission and entering ICU. The chest computed tomography (CT) findings of 3 patients were acute interstitial pneumonia, bronchopneumonia and lung consolidation, of which 2 cases were accompanied by a small amount of pleural effusion, and 1 case was accompanied by more regular small air sacs. Multiple lung lobes were involved, but mainly one lung lobe. The oxygenation index (PaO2/FiO2) of the 3 patients admitting to ICU were 100.0, 57.5 and 105.4 mmHg (1 mmHg ≈ 0.133 kPa), respectively, which met with the diagnostic criteria of moderate and severe acute respiratory distress syndrome (ARDS). All three patients received endotracheal intubation and mechanical ventilation. Under the bedside bronchoscope, the bronchial mucosa of 3 patients were obviously congested and edematous, without purulent secretion, and there was 1 case with mucosal hemorrhage. Three patients underwent bedside diagnostic bronchoscopy, and the evaluation result of the pathogen was that it might be atypical pathogen infection, so they were given moxifloxacin, cisromet and doxycycline intravenously, respectively, and combined with carbapenem antibiotics intravenously. After 3 days, the detection results of mNGS in bronchoalveolar lavage fluid (BALF) showed that only Chlamydia psittaci was infected. At this time, the condition was significantly improved, and PaO2/FiO2 was significantly increased. Therefore, the antibiotic treatment scheme remained unchanged, and mNGS only served to verify the initial diagnosis. Two patients were extubated on the 7th and 12th day of admission to the ICU, respectively, while one patient was extubated on the 16th day of admission to the ICU due to nosocomial infection. All 3 patients were transferred to the respiratory ward after the condition was stable. CONCLUSIONS: The bedside diagnostic bronchoscopy based on clinical characteristics is conducive to not only the rapid assessment of the early pathogens of severe Chlamydia psittaci pneumonia, but also effective anti-infection treatment before the returning of mNGS test results, which can make up for the lag and uncertainty of the mNGS test results.

Semi-blind calibration for orbital angular momentum generating system using maximal likelihood estimation.

Generating a high quality vortex beam carrying orbital angular momentum (OAM) is of importance in the application of the OAM to target detections or communications. This paper presents a semi-blind method to calibrate the uniform circle array (UCA) OAM generating system by using a virtual receiving sensor array without knowing the precise position of this auxiliary array. A low computational complexity algorithm is proposed to solve the maximum likelihood estimate (MLE) for the amplitude and phase errors of the transducers of the UCA based on the separation of parameters to be estimated. Moreover, this MLE is proved to be related to the beamforming of the virtual array. Simulations indicate that this method can estimate the mismatch parameters of the UCA effectively, and experiments in an anechoic tank show that the OAM generating system can generate a desirable vortex beam after we compensate each transducer of the UCA.

Safety and efficacy of nimodipine combined with flunarizine in patients with angioneurotic headache.

OBJECTIVE: To observe the role of nimodipine combined with flunarizine on angioneurotic headache. METHODS: Altogether 101 patients with angioneurotic headache were divided into the control group (CG, n=51) and the therapy group (TG, n=50). Patients in the CG were given nimodipine, while patients in the TG were given flunarizine on the basis of nimodipine. The clinical efficacy and adverse reactions of patients were observed. RESULTS: After treatment, the Visual analog scale (VAS) scores of the TG were markedly lower than those in the CG, and the number of attacks and headache duration of patients in the TG were also markedly reduced. Observation of the clinical efficacy showed that the effective rate of the TG was markedly higher than that of the CG, but no additional adverse reactions were found. In addition, after treatment, the cerebral hemodynamics and quality of life of patients were improved. CONCLUSION: Nimodipine combined with flunarizine can better promote the recovery of patients with angioneurotic headache and improve their quality of life.

On the rejection of internal and external disturbances in a wind energy conversion system with direct-driven PMSG.

This paper deals with the critical issue in a wind energy conversion system (WECS) based on a direct-driven permanent magnet synchronous generator (PMSG): the rejection of lumped disturbance, including the system uncertainties in the internal dynamics and unknown external forces. To simultaneously track the motor speed in real time and capture the maximum power, a maximum power point tracking strategy is proposed based on active disturbance rejection control (ADRC) theory. In real application, system inertia, drive torque and some other parameters change in a wide range with the variations of disturbances and wind speeds, which substantially degrade the performance of WECS. The ADRC design must incorporate the available model information into an extended state observer (ESO) to compensate the lumped disturbance efficiently. Based on this principle, a model-compensation ADRC is proposed in this paper. Simulation study is conducted to evaluate the performance of the proposed control strategy. It is shown that the effect of lumped disturbance is compensated in a more effective way compared with the traditional ADRC approach.