A theory of seepage instability was used to estimate the harmfulness of water-inrush from a coal seam floor in a particular coal mine of the Mining Group,Xuzhou. Based on the stratum column chart in this coal mine,the...A theory of seepage instability was used to estimate the harmfulness of water-inrush from a coal seam floor in a particular coal mine of the Mining Group,Xuzhou. Based on the stratum column chart in this coal mine,the distribu-tion of stress in mining floors when the long-wall mining was respectively pushed along to 100 m and to 150 m was simulated by using the numerical software (RFPA2D). The permeability parameters of the coal seam floor are described given the relationship between permeability parameters. Strain and the water-inrush-indices were calculated. The wa-ter-inrush-index was 67.2% when the working face was pushed to 100 m,showing that water-inrush is possible and it was 1630% when the working face was pushed to 150 m,showing that water-inrush is quite probable. The results show that as long-wall mining is pushed along,the failure zone is enlarged,the strain increased,and fissures developed cor-respondingly,resulting in the formation of water-inrush channels. Accompanied by the failure of the strata,the perme-ability increased exponentially. In contrast,the non-Darcy flow β factor and the acceleration coefficient decreased ex-ponentially,while the increase in the water-inrush-index was nearly exponential and the harmfulness of water-inrush in the coal mine increased accordingly.展开更多
To define the diffusion behavior of harmful exhaust substances from diesel vehicles and support safety risk assessments of underground coal mines,we performed a multi-species coupling calculation of the emission and d...To define the diffusion behavior of harmful exhaust substances from diesel vehicles and support safety risk assessments of underground coal mines,we performed a multi-species coupling calculation of the emission and diffusion of harmful substances from a trackless rubber-wheel diesel vehicle.A computational fluid dynamics(CFD)model of the diffusion of harmful emissions was hence established and verified.From the perspective of risk analysis,the diffusion behavior and distribution of hazardous substances emitted by the diesel vehicle were studied under 4 different conditions;moreover,we identified areas characterized by hazardous levels of emissions.When the vehicle idled upwind in the roadway,high-risk areas formed behind and to the right of the vehicle:particularly high concentrations of pollutants were measured near the rear floor of the vehicle and within 5 m behind the vehicle.When the vehicle idled downwind,high-risk areas formed in front of it:particularly high concentrations of pollutants were measured near the floor and within 5 m from the front of the vehicle.In the above cases,the driver would not breathe highly polluted air and would be relatively safe.When the vehicle idled into the chamber,however,high-risk areas formed on both sides of the vehicle and near the upper roof.Forward entry of the vehicle caused a greater increase in the concentration of pollutants in the chamber and in the driver’s breathing zone compared with reverse entry.展开更多
骨关节炎作为最常见的退行性肌骨系统疾病,全球疾病负担正日益加重。2019年,全球约5.3亿人受到骨关节炎困扰,其年龄标化发病率、标化患病率及标化伤残调整寿命年(disability-adjusted life years,DALYs)率分别为492.2/10万、6348.3/10万...骨关节炎作为最常见的退行性肌骨系统疾病,全球疾病负担正日益加重。2019年,全球约5.3亿人受到骨关节炎困扰,其年龄标化发病率、标化患病率及标化伤残调整寿命年(disability-adjusted life years,DALYs)率分别为492.2/10万、6348.3/10万及228.0/10万。高收入北美地区的骨关节炎疾病负担最重;而高收入亚太地区的疾病负担增长速度最快。我国骨关节炎年龄标化发病率、标化患病率及标化DALYs率分别为509.8/10万、6330.1/10万及224.8/10万,高于亚洲平均水平。考虑庞大的人口基数与人口老龄化趋势,我国骨关节炎负担将进一步加重,预计2044年患病人数和DALYs将增至2019年的1.5倍。骨关节炎常见于中老年人,但近年来研究显示,其对年轻劳动人群的影响亦不可忽视。此外,绝经后女性、高体质量指数人群及农村与山区居民的骨关节炎发生风险相对较高。骨关节炎不仅增加了肌少症与骨折等肌骨疾病的发生风险,也增加了心血管疾病、糖尿病及心理认知障碍等多学科疾病的发生风险。未来我国骨关节炎疾病负担及相关医疗需求将进一步增加,临床医生应在全面了解骨关节炎疾病负担与危害的基础上,在治疗骨关节炎的同时,积极筛查、监测并及时干预其他相关疾病,减轻骨关节炎患者的疾病负担,尽力改善其生活质量。展开更多
基金Projects 50225414 supported by the National Outstanding Youth Foundation50574090, 50674087 and 50490270 by the National Natural Science Foundation of China
文摘A theory of seepage instability was used to estimate the harmfulness of water-inrush from a coal seam floor in a particular coal mine of the Mining Group,Xuzhou. Based on the stratum column chart in this coal mine,the distribu-tion of stress in mining floors when the long-wall mining was respectively pushed along to 100 m and to 150 m was simulated by using the numerical software (RFPA2D). The permeability parameters of the coal seam floor are described given the relationship between permeability parameters. Strain and the water-inrush-indices were calculated. The wa-ter-inrush-index was 67.2% when the working face was pushed to 100 m,showing that water-inrush is possible and it was 1630% when the working face was pushed to 150 m,showing that water-inrush is quite probable. The results show that as long-wall mining is pushed along,the failure zone is enlarged,the strain increased,and fissures developed cor-respondingly,resulting in the formation of water-inrush channels. Accompanied by the failure of the strata,the perme-ability increased exponentially. In contrast,the non-Darcy flow β factor and the acceleration coefficient decreased ex-ponentially,while the increase in the water-inrush-index was nearly exponential and the harmfulness of water-inrush in the coal mine increased accordingly.
基金supported by the National Natural Science Foundation of China(Nos.52174191 and 51874191)the National Key R&D Program of China(No.2017YFC0805201)+1 种基金Qingchuang Science and Technology Project of Shandong Province University(No.2020KJD002)Taishan Scholars Project Special Funding(No.TS20190935).
文摘To define the diffusion behavior of harmful exhaust substances from diesel vehicles and support safety risk assessments of underground coal mines,we performed a multi-species coupling calculation of the emission and diffusion of harmful substances from a trackless rubber-wheel diesel vehicle.A computational fluid dynamics(CFD)model of the diffusion of harmful emissions was hence established and verified.From the perspective of risk analysis,the diffusion behavior and distribution of hazardous substances emitted by the diesel vehicle were studied under 4 different conditions;moreover,we identified areas characterized by hazardous levels of emissions.When the vehicle idled upwind in the roadway,high-risk areas formed behind and to the right of the vehicle:particularly high concentrations of pollutants were measured near the rear floor of the vehicle and within 5 m behind the vehicle.When the vehicle idled downwind,high-risk areas formed in front of it:particularly high concentrations of pollutants were measured near the floor and within 5 m from the front of the vehicle.In the above cases,the driver would not breathe highly polluted air and would be relatively safe.When the vehicle idled into the chamber,however,high-risk areas formed on both sides of the vehicle and near the upper roof.Forward entry of the vehicle caused a greater increase in the concentration of pollutants in the chamber and in the driver’s breathing zone compared with reverse entry.
文摘骨关节炎作为最常见的退行性肌骨系统疾病,全球疾病负担正日益加重。2019年,全球约5.3亿人受到骨关节炎困扰,其年龄标化发病率、标化患病率及标化伤残调整寿命年(disability-adjusted life years,DALYs)率分别为492.2/10万、6348.3/10万及228.0/10万。高收入北美地区的骨关节炎疾病负担最重;而高收入亚太地区的疾病负担增长速度最快。我国骨关节炎年龄标化发病率、标化患病率及标化DALYs率分别为509.8/10万、6330.1/10万及224.8/10万,高于亚洲平均水平。考虑庞大的人口基数与人口老龄化趋势,我国骨关节炎负担将进一步加重,预计2044年患病人数和DALYs将增至2019年的1.5倍。骨关节炎常见于中老年人,但近年来研究显示,其对年轻劳动人群的影响亦不可忽视。此外,绝经后女性、高体质量指数人群及农村与山区居民的骨关节炎发生风险相对较高。骨关节炎不仅增加了肌少症与骨折等肌骨疾病的发生风险,也增加了心血管疾病、糖尿病及心理认知障碍等多学科疾病的发生风险。未来我国骨关节炎疾病负担及相关医疗需求将进一步增加,临床医生应在全面了解骨关节炎疾病负担与危害的基础上,在治疗骨关节炎的同时,积极筛查、监测并及时干预其他相关疾病,减轻骨关节炎患者的疾病负担,尽力改善其生活质量。
