Influence of environmental parameters on workers' dust inhalation in underground mines.

Much dust is generated in underground coal mining processes, posing threats to workers' health and safety production. Dust enters the human body mainly through inhalation, primarily determined by the dust concentration around workers. In this study, the airflow field and dust distribution in the tunnel are simulated with FLUENT software. The breathing zone for a worker was defined to clarify the extent of external dust distribution influencing dust inhalation. The effects of human respiration, dust production rates, air supply velocities, and workers' positions on dust concentration in the breathing zone were investigated. The results show that there is upward airflow around the worker standing in the center of the air circulation. Human breath barely influences the airflow distribution and respirable dust concentrations in the breathing zone. Reducing the dust production rate in the tunnel can decrease the respirable dust concentration in the breathing zone by almost the same proportion. While increasing the air supply velocity by 50% would reduce only 20% of dust in the breathing zone. The dust concentrations vary along the roadway, in which the low concentration zone is located in the middle, more than 1.0 m away from the dust-producing surface and the wind surface. The research contributes to reducing workers' dust exposure with suggestions regarding ventilation optimization and working position selection.

Field measurement and numerical simulation of dust migration in a high-rise building of the mine hoisting system.

Dust pollutants generated from the coal transfer process in a high-rise building of the mine hoisting system not only undermine the operating environment but also reduce the surrounding air quality. Therefore, this study aimed to determine the spatiotemporal distribution of coal dust in the high-rise buildings using field measurement and numerical simulation. Based on the discrete phase model (DPM), the dust migration process under the hybrid ventilation system was investigated in detail. Then, the feasibility of the established model to predict the spatiotemporal distribution of dust pollutants was proven through the measurements of both the airflow and the dust concentration. The present study showed that dust distribution is not uniform in time and space, which also differs for different floors. The dust concentration of the 3rd floor is relatively larger when compared with those of other floors. The dust concentration increases for the upper floors when the upward air velocity increases, while those of the lower floors are not always low due to the backflows, particularly for the 2nd floor. PM2.5 takes up more than 20% of all discharged particles.

Sagittal Atlantoaxial Joint Inclination and Reduction Index Values for Diagnosis and Treatment of Irreducible Atlantoaxial Dislocation.

BACKGROUND: Irreducible atlantoaxial dislocation (IAAD) is a disorder of atlantoaxial joint instability with various causes. The diagnostic criteria for IAAD are variable. The diagnosis of IAAD is mainly based on preoperative and intraoperative traction results, as well as the physician's experience, with no relatively uniform guidelines for the selection of treatment. This study evaluates sagittal atlantoaxial joint inclination (SAAJI) and reduction index (RI) values for diagnosis and treatment of IAAD. MATERIALS AND METHODS: 24 IAAD patients treated in our hospital from January 2008 to July 2014 were retrospectively analysed. Patients included were 13 males and 11 females, with a mean age of 43 years. The various causes for IAAD were atlantoaxial transverse ligament rupture (n=3), old dens fracture (n=15), occipitalization of the atlas (n=6). The patients were divided into two groups. group A underwent anterior release with posterior reduction and fixation; Group B underwent posterior reduction and fixation; 12 healthy individuals served as controls. SAAJI and atlas-dens interval (ADI) values before and after traction were measured, and RI was calculated. Imaging data were analyzed. RESULTS: The mean SAAJI values were as follows: left, 5.6 ± 1.9° and right, 5.1 ± 2.1° in the control group; right, 39.5 ± 6.0° and left, 38.8 ± 5.8° in Group A; and right, 23.1 ± 7.0° and left, 23.9 ± 6.1° in Group B. There was no significant difference in the SAAJI values of the three groups (P < 0.05). The mean RIs in Groups A and B were 17.6 ± 9.3% and 34.4 ± 5.2%, respectively, and the difference was statistically significant (P < 0.05). There were obvious negative correlations between the SAAJI and RI values in Groups A and B. CONCLUSIONS: SAAJI and RI can be used as important imaging indicators to determine the reversibility of IAAD. If the RI value is >27.9% and SAAJI value is <32.5°, reduction and fixation can be achieved by the posterior approach alone; otherwise, a combination of anterior and posterior approaches would be necessary.