An Orderly Untangling Model against Arching Effect in Emergency Evacuation Based on Equilibrium Partition of Crowd

To untangle the arching effect of a crowd as much as possible in emergency evacuations, we employ a theoretical model of equilibrium partition of crowd batch. Based on the shortest time arrangement of evacuation, the crowd is divided into appropriate batches according to the occupied time of evacuation channel in order to determine the occupant number of every evacuation passageway. The number of each batch crowd is calculated under the condition that the time of entering the evacuation passageway is equal to the time of crossing over the evacuation passageway. Subsequently, the shortest processing time (SPT) rule establishes the evacuation order of each batch. Taking a canteen of China Three Gorges University as a background, we obtain the waiting time from the first person to the last one entering the evacuation channel in every batch by simulation. This research utilizes data from simulations to observe an untangling process against the arching effect based on the SPT rule. More specifically, evacuation time only lasts for 180.1 s in order and is 1.6 s longer than that in disorder, but the arching effect disappears. Policy recommendations are offered to improve the evacuation scheme in disaster operations

Primary pulmonary meningioma presenting as a pulmonary ground glass nodule: a case report and review of the literature

Abstract Background A primary pulmonary meningioma is an extremely rare entity. Primary pulmonary meningiomas manifested with a ground glass nodule are a very rare occurrence in clinical practice. Case presentation In this study, we report a case of a primary pulmonary meningioma with atypical computed tomography features. A 59-year-old Han Chinese female came to our hospital for treatment and reported that her physical examination revealed a ground glass nodule in the right lung for over 3 months. The histologic result revealed a primary pulmonary meningioma. The patient underwent a thoracoscopic lung wedge resection of the right upper lobe for a ground glass nodule. After 1 year of follow-up, the patient is still alive without evidence of metastasis or recurrence. Conclusions Primary pulmonary meningiomas could have a variety of radiological findings. As there are no specific radiologic features for the diagnosis of primary pulmonary meningiomas, complete resection of the lesion is required for both diagnosis and treatment. It is necessary to note the imaging features of primary pulmonary meningiomas, presenting as a ground glass nodule; this rare tumor should be considered in differential diagnoses

Study on the difference of water-bearing capacity of fault-controlled dolomites in Dengying Formation of a mining area in central Guizhou and its significance of water control

The central region of Guizhou Province enjoys global fame of its areas with large-scale production rich in phosphorus. For a long time, the phosphate rock resources in this area have provided a reliable guarantee for the domestic economic development. At present, this region has also become an important raw material base of phosphate rocks and a production base of fine phosphate chemicals in China. After decades of mining, phosphorus mines in this area have gradually changed from open pits to underground ones and from shallow to deep, and thus the hydrogeological conditions of deposits become increasingly complex. Dengying Formation, the main aquifers of phosphate rocks, is composed of dolomite with the water-bearing medium of solution pores and cracks. It is a water-bearing formation comprised of pure carbonate rocks with medium to high water abundance. Consequently, the high cost of mine drainage has imposed a heavy burden on mining enterprises. In addition, mine water inrush has severely threatened the exploitation safety of phosphate rock resources in this region. Therefore, it is very important to research the characteristics of water abundance of the Dengying Formation. The phosphate mine of Dawan, a water-filling deposit with deeply covered karst, is located on the western flank of the Baiyan anticline. The high bearing capacity of groundwater and complicated hydrogeological conditions of Dengying Formation are representative and typical in the Baiyan anticline area. Due to the super large scale and high grade of phosphate ore resources, the phosphate mine of Dawan was listed as a key project of mineral resource exploration in Guizhou Province in 2020. During the exploration work, a large amount of geological data was obtained through surface surveys, geophysical and hydrological logging, drilling, and hydrogeological experiments. In this paper, a study on the water abundance of the Dengying Formation of the deposit has been conducted based on the data from the exploration of the phosphate mine as well as the anatomy of typical mining areas. The research results show that the phosphate mine in Dawan is a karst deposit with water-filled roof, and the lithology, structure and fracture structure of the Dengying Formation in the water-filled layer are the main factors controlling the water-filling condition of the deposit. With an obvious distribution law, the water content and permeability of Dengying Formation present obvious characteristics of "plane partition" and "vertical stratification". In the plane of exploration area, there is a significant difference in water abundance of the Dengying Formation near and far from the structural area. The differences in fault properties also result in different water abundance of the Dengying Formation. In the vertical direction, there is a weak permeable layer with poor water content and relative water resistance in the middle and lower parts of the Dengying Formation. The waterproof design of mine based on the characteristics of water abundance in Dengying Formation is of great significance to ensure the safe production of the phosphate mine in central Guizhou, and to reduce the cost of mining drainage

Prediction and Optimization of the Long-Term Fatigue Life of a Composite Hydrogen Storage Vessel Under Random Vibration

A composite hydrogen storage vessel (CHSV) is one key component of the hydrogen fuel cell vehicle, which always suffers random vibration during transportation, resulting in fatigue failure and a reduction in service life. In this paper, firstly, the free and constrained modes of CHSV are experimentally studied and numerically simulated. Subsequently, the random vibration simulation of CHSV is carried out to predict the stress distribution, while Steinberg’s method and Dirlik’s method are used to predict the fatigue life of CHSV based on the results of stress distribution. In the end, the optimization of ply parameters of the composite winding layer was conducted to improve the stress distribution and fatigue life of CHSV. The results show that the vibration pattern and frequency of the free and constrained modes of CHSV obtained from the experiment tests and the numerical predictions show a good agreement. The maximum difference in the value of the vibration frequency of the free and constrained modes of CHSV from the FEA and experiment tests are, respectively, 8.9% and 8.0%, verifying the accuracy of the finite element model of CHSV. There is no obvious difference between the fatigue life of the winding layer and the inner liner calculated by Steinberg’s method and Dirlik’s method, indicating the accuracy of FEA of fatigue life in the software Fe-safe. Without the optimization, the maximum stresses of the winding layer and the inner liner are found to be near the head section by 469.4 MPa and 173.0 MPa, respectively, and the numbers of life cycles of the winding layer and the inner liner obtained based on the Dirlik’s method are around 1.66 × 106 and 3.06 × 106, respectively. Through the optimization of ply parameters of the composite winding layer, the maximum stresses of the winding layer and the inner liner are reduced by 66% and 85%, respectively, while the numbers of life cycles of the winding layer and the inner liner both are increased to 1 × 107 (high cycle fatigue life standard). The results of the study provide theoretical guidance for the design and optimization of CHSV under random vibration

Quality of life and compensatory hyperhidrosis following thoracoscopic sympathectomy: a retrospective cohort study

Abstract Background Palmar hyperhidrosis (PH), characterized by excessive palm sweating, significantly impacts quality of life (QOL) in affected individuals, particularly young adults. This study aimed to evaluate the efficacy of video-assisted thoracoscopic sympathectomy (VATS) in improving symptoms and QOL among 816 patients with PH. Methods This retrospective study included 816 patients with PH, all of whom underwent VATS under general anaesthesia. One-year follow-up via phone surveys was used to assess symptom changes and side effects. Paired t tests were used to compare pre- and postoperative QOL scores, and linear regression was used to analyse the effects of various factors on QOL changes. Results The cohort consisted of 359 males and 457 females, with a mean age of 24.98 ± 6.47 years. All patients underwent VATS, with a 91% success rate, and the mean operative time was 53.2 ± 24.7 min. Postoperative complications included 43 cases of incision infections, 194 cases of chest pain, and 82 cases of pneumothorax; compensatory hyperhidrosis (CH) occurred in 53.80% of the T3 group and 43.74% of the T4 group after one month, with significant differences noted at the 24-month follow-up. Furthermore, the QOL scores significantly improved from 38.25 ± 3.61 preoperatively to 69.07 ± 3.48 at one year postoperatively (P < 0.05). Conclusions VATS offers a reliable and effective treatment for severe PH, significantly enhancing patients’ overall QOL. Future research should focus on long-term outcomes and the applicability of this treatment across diverse populations to further advance the clinical management of PH

Impact Resistance Behaviors of Carbon Fiber Fabric Reinforced Composite Laminates with Bio-Inspired Helicoidal Layups

Carbon fiber fabric reinforced composite laminates are widely used in the automotive and aerospace components, which are prone to suffering low velocity impacts. In this paper, helicoidal layups of fabrics inspired by the Bouligand type structure of the dactyl clubs of mantis shrimp are proposed to improve the impact resistance of carbon fiber fabric reinforced composite laminates. Low velocity impact tests and finite element simulation are carried out to investigate the effect of the rotation angle of helicoidal layups on the impact damage behaviors of composite laminates, including impact force response, energy absorption characteristics and damage mechanism. Results show that the simulation results of impact force&ndash;time response, absorbed energy&ndash;time response, and damage characteristics show good agreements with the experimental results. With the increase in impact energy, the maximum value of impact force, the absorbed energy and the energy absorption ratio for all specimens are all increased. Under all impact energies, the impact damage of specimens with helicoidal layups are lower than that of specimen QI1 (rotation angle of 0&deg;), indicating that the helical layup of woven carbon fabric can sufficiently enhance the impact resistance of the composite material. Furthermore, the impact resistance of specimen HL2 (rotation angle of 12.8&deg;) is the best, because it demonstrates the lowest impact damage and highest impact force under all energies. This work provides a bionic design guideline for the high impact performance of carbon fiber fabric reinforced composite laminate

Simulation and Experiment on the Low-Velocity Impact Response of Flax Fabric Reinforced Composites

Natural fiber reinforced composites are increasingly used to fabricate structural components prone to suffering low-velocity impacts. The low-velocity impact response of flax fabric reinforced composites under different impact energies is experimentally studied and numerically simulated. A multi-scale finite element analysis strategy for the progressive damage prediction of flax fabric reinforced composites is developed. Micro- and meso-scale analyses are conducted to predict the effective properties of the woven unit cell. Macro-scale analysis is carried out subsequently to predict the impact response of composite laminates using the results of micro- and meso-scale analyses as inputs. Simulation results and experimental results both show that most of the impact energy is absorbed by the specimens when the impact energy is lower than 4 J, and the absorption ratio of impact energy slightly increases with the increase in impact energy. On the contrary, a dramatic decrease occurs in the absorption ratio when the impact energy is 6 J, due to the severe damage to the specimen. In addition, simulation results indicate that matrix shear damage and interlaminar damage are the primary failure modes of composites under high impact energy. The numerical results of impact force, absorbed energy, and damage morphologies on both sides for all specimens show good agreement with the experimental results