This paper analyzes the control mechanism of coal and gas outbursts and proposes the concept of an effective pressure relief protection range, based on the stress relief of the underlying coal-rock mass and the develo...This paper analyzes the control mechanism of coal and gas outbursts and proposes the concept of an effective pressure relief protection range, based on the stress relief of the underlying coal-rock mass and the development of a plastic zone. Also this study developed a stress change and fracture development model of the underlying coal-rock mass. In addition, the stress and depth of fracture of any point in the floor were deduced with the application of Maple Calculation Software. The specific engineering parameters of the Pingdingshan No. 12 colliery were applied to determine the relationship between the depth of fracture in the floor and the mining height. The pressure-relief principle of the underlying coal-rock mass was analyzed while varying the mining height of the upper protective seam. The findings indicate that as the depth of fracture in the floor increases, the underlying coal-rock mass experiences a limited amount of pressure relief, and the pressure relief protection range becomes narrower.Additionally, the stress distribution evolves from a ‘‘U" shape into a ‘‘V" shape. A 2.0 m mining height of protective seam situates the outburst-prone seam, Ji_(15), within the effective pressure relief protection range. The fracture development and stress-relief ratio rises to 88%, ensuring the pressure-relief effect as well as economic benefits. The measurement data show that: after mining the upper protective seam, the gas pressure of Ji_(15) dropped from 1.78 to 0.35 MPa, demonstrating agreement between the engineering application and the theoretical calculation.展开更多
<b>Background & Aims:</b> The multimodal analgesia provides superior pain relief and reduces opioid consumption and its side effects. Gabapentin has been used successfully in multi-modal analgesia in d...<b>Background & Aims:</b> The multimodal analgesia provides superior pain relief and reduces opioid consumption and its side effects. Gabapentin has been used successfully in multi-modal analgesia in different doses. We designed a double-blind randomized control trial to find the minimal effective dose of gabapentin in multimodal analgesia for postoperative pain following total abdominal hysterectomy. <b>Material & Methods:</b> After informed consent, total of 87 patients were randomly assigned to A, B & C groups to receive gabapentin orally 300 mg, 600 mg, and 900 mg respectively one to two hours before surgery. Postoperatively pain was managed by patient-controlled analgesia (PCA) using pethidine. Pain score, opioid consumption, and side effects of gabapentin were monitored. Rescue analgesia was given and monitored. <b>Results:</b> There was no statistically significant difference among the groups with respect to age, weight, height, pethidine consumption, and rescue analgesia. Mean pain scores were statistically insignificant at baseline, 8, 12, and 24 hours postoperatively. Only at 4 hours, the highest pain score (mean) was found in group A, which is statistically significant. The side effects of gabapentin like nausea, vomiting, somnolence, and dizziness were also statistically insignificant. <b>Conclusion:</b> A single preoperative oral gabapentin 300 mg was found to be minimal effective dose in multimodal analgesic regimen for reducing post-operative pain and analgesic requirement following total abdominal hysterectomy.展开更多
With the development of coal mine equipment mechanization, the wide application of </span><span style="font-family:Verdana;">“</span><span style="font-family:Verdana;">...With the development of coal mine equipment mechanization, the wide application of </span><span style="font-family:Verdana;">“</span><span style="font-family:Verdana;">hole instead of roadway</span><span style="font-family:Verdana;">”</span><span style="font-family:Verdana;"> technology greatly reduces the cost of gas control engineering, but puts forward higher requirements for the effect of gas drainage. At present, the drainage effect of coal mine inspection boreholes is mainly evaluated by the drilling field, but the flow rate and gas concentration of each borehole in the drilling field are not the same, which causes the gas drainage effect not to be correctly mastered. In the present study, the pressure relief drilling in the goaf of the working face of a typical multi-coal seam group high gas outburst mining area was taken as the research object. Through the newly developed portable drilling inspection device, the pure amount of drilling drainage was investigated, and the drilling design was dynamically adjusted. The enhancement of the goaf pressure relief gas control effect ensures the gas safety of the mining face. At the same time, this improves the gas extraction rate and reduces the emission of greenhouse gases. If the data from the borehole investigation can be transmitted in real time and analyzed in big data, the optimal extraction negative pressure can be predicted through a regression algorithm. Under the control of the negative pressure of each borehole by the actuator, the extraction system can have the function of intelligent judgment.展开更多
基金supported by the Foundation for Distinguished professor of Jiangsu Provincethe Foundation for Innovative Research Groups of the National Natural Science Foundation of China (No.51421003)
文摘This paper analyzes the control mechanism of coal and gas outbursts and proposes the concept of an effective pressure relief protection range, based on the stress relief of the underlying coal-rock mass and the development of a plastic zone. Also this study developed a stress change and fracture development model of the underlying coal-rock mass. In addition, the stress and depth of fracture of any point in the floor were deduced with the application of Maple Calculation Software. The specific engineering parameters of the Pingdingshan No. 12 colliery were applied to determine the relationship between the depth of fracture in the floor and the mining height. The pressure-relief principle of the underlying coal-rock mass was analyzed while varying the mining height of the upper protective seam. The findings indicate that as the depth of fracture in the floor increases, the underlying coal-rock mass experiences a limited amount of pressure relief, and the pressure relief protection range becomes narrower.Additionally, the stress distribution evolves from a ‘‘U" shape into a ‘‘V" shape. A 2.0 m mining height of protective seam situates the outburst-prone seam, Ji_(15), within the effective pressure relief protection range. The fracture development and stress-relief ratio rises to 88%, ensuring the pressure-relief effect as well as economic benefits. The measurement data show that: after mining the upper protective seam, the gas pressure of Ji_(15) dropped from 1.78 to 0.35 MPa, demonstrating agreement between the engineering application and the theoretical calculation.
文摘<b>Background & Aims:</b> The multimodal analgesia provides superior pain relief and reduces opioid consumption and its side effects. Gabapentin has been used successfully in multi-modal analgesia in different doses. We designed a double-blind randomized control trial to find the minimal effective dose of gabapentin in multimodal analgesia for postoperative pain following total abdominal hysterectomy. <b>Material & Methods:</b> After informed consent, total of 87 patients were randomly assigned to A, B & C groups to receive gabapentin orally 300 mg, 600 mg, and 900 mg respectively one to two hours before surgery. Postoperatively pain was managed by patient-controlled analgesia (PCA) using pethidine. Pain score, opioid consumption, and side effects of gabapentin were monitored. Rescue analgesia was given and monitored. <b>Results:</b> There was no statistically significant difference among the groups with respect to age, weight, height, pethidine consumption, and rescue analgesia. Mean pain scores were statistically insignificant at baseline, 8, 12, and 24 hours postoperatively. Only at 4 hours, the highest pain score (mean) was found in group A, which is statistically significant. The side effects of gabapentin like nausea, vomiting, somnolence, and dizziness were also statistically insignificant. <b>Conclusion:</b> A single preoperative oral gabapentin 300 mg was found to be minimal effective dose in multimodal analgesic regimen for reducing post-operative pain and analgesic requirement following total abdominal hysterectomy.
文摘With the development of coal mine equipment mechanization, the wide application of </span><span style="font-family:Verdana;">“</span><span style="font-family:Verdana;">hole instead of roadway</span><span style="font-family:Verdana;">”</span><span style="font-family:Verdana;"> technology greatly reduces the cost of gas control engineering, but puts forward higher requirements for the effect of gas drainage. At present, the drainage effect of coal mine inspection boreholes is mainly evaluated by the drilling field, but the flow rate and gas concentration of each borehole in the drilling field are not the same, which causes the gas drainage effect not to be correctly mastered. In the present study, the pressure relief drilling in the goaf of the working face of a typical multi-coal seam group high gas outburst mining area was taken as the research object. Through the newly developed portable drilling inspection device, the pure amount of drilling drainage was investigated, and the drilling design was dynamically adjusted. The enhancement of the goaf pressure relief gas control effect ensures the gas safety of the mining face. At the same time, this improves the gas extraction rate and reduces the emission of greenhouse gases. If the data from the borehole investigation can be transmitted in real time and analyzed in big data, the optimal extraction negative pressure can be predicted through a regression algorithm. Under the control of the negative pressure of each borehole by the actuator, the extraction system can have the function of intelligent judgment.
