It is a commonly asked question:how big should the longwall shields be? The answer is a key aspect of a longwall mining feasibility study when the consequences of inadequately rated shields are considered.This paper a...It is a commonly asked question:how big should the longwall shields be? The answer is a key aspect of a longwall mining feasibility study when the consequences of inadequately rated shields are considered.This paper addresses this question based on the measured nature of the loading environment in which shields are required to operate,the various geological and geometrical controls of that environment and the various links between their load rating,a range of other relevant shield design factors and the loss event they are required to prevent a major roof collapse on the longwall face.The paper concludes that despite the tremendous advances that have been made in shield design and load rating over the past50 years,the same drivers that caused longwall miners of the past to seek improved roof control on the longwall face via the use of ever-higher rated shields,are still as relevant today.However at the current time,the limits of the largest available longwall shields have yet to be tested,therefore industry focus for the foreseeable future should possibly be in achieving the maximum level of roof control on the face via their optimum operational use rather than considering further shield rating increases and incurring the inevitable downsides in terms of capital cost and shield weight.展开更多
AIM:To investigate the possible reasons and suggest therapeutic plan of stress-induced intestinal necrosis resulting from the severe trauma.METHODS:Three patients in our study were trapped inside collapsed structures ...AIM:To investigate the possible reasons and suggest therapeutic plan of stress-induced intestinal necrosis resulting from the severe trauma.METHODS:Three patients in our study were trapped inside collapsed structures for 22,21 and 37 h,respectively,The patients underwent 3-4 operations after sustaining their injuries,Mechanical ventilation,intermittent hemodialysis and other treatments were also provided.The patients showed signs of peritoneal irritation on postoperative days 10-38.Small intestinal necrosis was confirmed by emergency laparotomy,and for each patient,part of the small bowel was removed.RESULTS:Two patients who all performed 3 operations died of respiratory complications on the first and second postoperative days respectively.The third patient who performed 4 operations was discharged and made a full recovery.Three patients had the following common characteristics:(1) Multiple severe trauma events with no direct penetrating gastrointestinal injury;(2) Multiple surgeries with impaired renal function and intermittent hemodialysis treatment;(3) Progressive abdominal pain and tenderness,and peritoneal irritation was present on post-traumatic days 10-38;(4) Abdominal operations confirmed segment ulcer,necrosis of the small intestine,hyperplasia and stiffness of the intestinal wall;and(5) Pathological examinations suggested submucosal hemorrhage,necrosis,fibrosis and hyalinization of the vascular wall.Pathological examinations of all 3 patients suggested intestinal necrosis with fistulas.CONCLUSION:Intestinal necrosis is strongly associated with stress from trauma and post-traumatic complications;timely exploratory laparotomy maybe an effective method for preventing and treating stressinduced intestinal necrosis.展开更多
The mechanical properties of the pelvic trabecular bone have been studied at the continuum level. However, nothing is known about the tissue-level damage in the trabecular bone of the healthy human acetabulum at appar...The mechanical properties of the pelvic trabecular bone have been studied at the continuum level. However, nothing is known about the tissue-level damage in the trabecular bone of the healthy human acetabulum at apparent small strains characteristic of habitual. By a DAWING 4000 A supercomputer, nonlinear micro-finite element (μFE) analysis was performed to quantify tissue-level damage accumulation in trabecular bone at small strains. The data indicate that damage in trabecular bone commence at 0.2% apparent strain. The findings imply that tissue yielding can initiate at very low strains in the trabecular bone of the healthy acetabulum and that this local failure has negative consequences on the apparent mechanical properties of trabecular bone.展开更多
文摘It is a commonly asked question:how big should the longwall shields be? The answer is a key aspect of a longwall mining feasibility study when the consequences of inadequately rated shields are considered.This paper addresses this question based on the measured nature of the loading environment in which shields are required to operate,the various geological and geometrical controls of that environment and the various links between their load rating,a range of other relevant shield design factors and the loss event they are required to prevent a major roof collapse on the longwall face.The paper concludes that despite the tremendous advances that have been made in shield design and load rating over the past50 years,the same drivers that caused longwall miners of the past to seek improved roof control on the longwall face via the use of ever-higher rated shields,are still as relevant today.However at the current time,the limits of the largest available longwall shields have yet to be tested,therefore industry focus for the foreseeable future should possibly be in achieving the maximum level of roof control on the face via their optimum operational use rather than considering further shield rating increases and incurring the inevitable downsides in terms of capital cost and shield weight.
基金Supported by The Fund of the People's Liberation Army Gen-eral Hospital of Chengdu Command,No.2011YG-B24
文摘AIM:To investigate the possible reasons and suggest therapeutic plan of stress-induced intestinal necrosis resulting from the severe trauma.METHODS:Three patients in our study were trapped inside collapsed structures for 22,21 and 37 h,respectively,The patients underwent 3-4 operations after sustaining their injuries,Mechanical ventilation,intermittent hemodialysis and other treatments were also provided.The patients showed signs of peritoneal irritation on postoperative days 10-38.Small intestinal necrosis was confirmed by emergency laparotomy,and for each patient,part of the small bowel was removed.RESULTS:Two patients who all performed 3 operations died of respiratory complications on the first and second postoperative days respectively.The third patient who performed 4 operations was discharged and made a full recovery.Three patients had the following common characteristics:(1) Multiple severe trauma events with no direct penetrating gastrointestinal injury;(2) Multiple surgeries with impaired renal function and intermittent hemodialysis treatment;(3) Progressive abdominal pain and tenderness,and peritoneal irritation was present on post-traumatic days 10-38;(4) Abdominal operations confirmed segment ulcer,necrosis of the small intestine,hyperplasia and stiffness of the intestinal wall;and(5) Pathological examinations suggested submucosal hemorrhage,necrosis,fibrosis and hyalinization of the vascular wall.Pathological examinations of all 3 patients suggested intestinal necrosis with fistulas.CONCLUSION:Intestinal necrosis is strongly associated with stress from trauma and post-traumatic complications;timely exploratory laparotomy maybe an effective method for preventing and treating stressinduced intestinal necrosis.
基金the National High Technology Research and Development Program (863) of China(No. 2006AA02A137the Postgraduate Creativity Foundation of Shanghai Jiaotong University (No. BXJ0730)
文摘The mechanical properties of the pelvic trabecular bone have been studied at the continuum level. However, nothing is known about the tissue-level damage in the trabecular bone of the healthy human acetabulum at apparent small strains characteristic of habitual. By a DAWING 4000 A supercomputer, nonlinear micro-finite element (μFE) analysis was performed to quantify tissue-level damage accumulation in trabecular bone at small strains. The data indicate that damage in trabecular bone commence at 0.2% apparent strain. The findings imply that tissue yielding can initiate at very low strains in the trabecular bone of the healthy acetabulum and that this local failure has negative consequences on the apparent mechanical properties of trabecular bone.
