According to the engineering features of higher pile-column bridge pier in mountainous area, a clamped beam mechanical model was set up by synthetically analyzing the higher pile-column bridge pier buckling mechanism....According to the engineering features of higher pile-column bridge pier in mountainous area, a clamped beam mechanical model was set up by synthetically analyzing the higher pile-column bridge pier buckling mechanism. Based on the catastrophe theory, the cusp catastrophe model of higher pile-column bridge pier was established by the determination of its potential fimction and bifurcation set equation, the necessary instability conditions of high pile-column bridge pier were deduced, and the determination method for column-buckling and lateral displacement of high pile-column bridge pier was derived. The comparison between the experimental and calculated results show that the calculated curves agree with testing curves and the method is reasonable and effective.展开更多
Excavation-and-support induced disturbances are likely to make water-enriched roofs to become weathered and fractured.The development and connection of cracks provide new water channels which may result in water loss,...Excavation-and-support induced disturbances are likely to make water-enriched roofs to become weathered and fractured.The development and connection of cracks provide new water channels which may result in water loss,seriously affecting the in-tegrity and stability of roofs,leading to incidents of roof fall.Control of water-enriched rocks surrounding coal drifts is quite diffi-cult in China.Based on the practical situation of a water-enriched roof of a coal drift in working face 112201 of the Meihuajing coal mine,we studied the deformation features of surrounding rocks and the development of fractured areas and analyzed the major reasons for the decrease in load-carrying capacity,indicating that the key to maintain roof stability of this kind of coal drift is water retention.In addition,we proposed a staged control technology consisting of:1) surface grouting;2) cable anchor strengthening and 3) roof grouting,which has proven to be successful in this practical application.Our study indicates that,after the problem of water loss from the water-enriched roof had been effectively solved,a combined support system with high performance bolts can maintain the stability of the bearing structure,resulting in the control of roof stability in this kind of coal drift.展开更多
This paper deals with the operation and performance of VSC （voltage source converter） based HVDC （high voltage direct current） interconnecting two extremely weak AC networks, the experience of Caprivilink project....This paper deals with the operation and performance of VSC （voltage source converter） based HVDC （high voltage direct current） interconnecting two extremely weak AC networks, the experience of Caprivilink project. It is shown in the paper that the HVDC converter automatically provides the supreme voltage and frequency stabilizing function when a critical situation is detected, no matter the disturbances appeared in sending end or receiving end AC networks. This supreme voltage and frequency stabilizing function makes it possible to avoid the blackout even if all the generators are tripped under an extra-ordinary worst contingency. By plots of recorded transients, the paper will show how the eventual blackouts are avoided.展开更多
Transport risk assessment for the environment has two important aspects--problem solving model and solution veracity. Problem solving model is larger understanding of tasks interconnection, which represents in itself ...Transport risk assessment for the environment has two important aspects--problem solving model and solution veracity. Problem solving model is larger understanding of tasks interconnection, which represents in itself partial solution of general risk assessment. Veracity of solution means how the results are consistent with the reality. By researching of both aspects, it rises many unanswered questions. It is concerned about verification and validation of risk assessment results. By risk assessment for the environment it is possible to meet wide variety of more or less good soluble problems. It exists simple problems based on risk assessment of common traffic accidents connected with service charge outflow. On the other site, it exists complex problems of risk assessment connected with dangerous goods transport by traffic or pipelines. By simple problems solving there are not many questions about risk assessment veracity. It is possible to determine traffic accidents frequencies and service charge outflows consequences on the basis of examined events in transportation with great veracity. By complex problems the situation is quite different. The frequencies of large accidents are very low but the consequences for the environment may be large. Both are encumbered by large level of uncertainty. That is why the question is rising. To what degree, it is in these cases correct to make decision based on risk assessment.展开更多
Hoffa fracture associated with ipsilateral femoral shaft fracture is very rare. Three cases of this rare type of injury were retrospectively reviewed. The sites of femoral shaft fractures and Hoffa fractures were docu...Hoffa fracture associated with ipsilateral femoral shaft fracture is very rare. Three cases of this rare type of injury were retrospectively reviewed. The sites of femoral shaft fractures and Hoffa fractures were documented. All femoral shall fractures were managed with internal tixation. The rate ofmisdiagnosis for the Hoffa fractures was documented. Functions of the affected knees were evaluated according to the modified Hospital for Special Surgery （HSS） scores at two years follow-up. Femoral fractures were either transverse or composite in all three cases. Ipsilateral Hoffa fractures occurred at medial condyle in two cases, and lateral condyle in one case. Only one Hoffa fracture was identified preoperatively. All the femoral shaft fiattures healed uneventfully. In the patient whose Hoffa fracture was correctly diagnosed, the modified HSS score was 94. In another patient, whose Hoffa fracture was treated by a second operation, the modified HSS score was 93. And in the third case, who refused additional operation for the Hoffa fracture, the modified HSS score was only 70. Conclusively femoral shall fracture can be associated with ipsilateral Hoffa fracture, especially in motorcycle accident. This type of iniury is very rare and misdiagnosis is common.展开更多
基金Project(50578060) supported by the National Natural Science Foundation of China
文摘According to the engineering features of higher pile-column bridge pier in mountainous area, a clamped beam mechanical model was set up by synthetically analyzing the higher pile-column bridge pier buckling mechanism. Based on the catastrophe theory, the cusp catastrophe model of higher pile-column bridge pier was established by the determination of its potential fimction and bifurcation set equation, the necessary instability conditions of high pile-column bridge pier were deduced, and the determination method for column-buckling and lateral displacement of high pile-column bridge pier was derived. The comparison between the experimental and calculated results show that the calculated curves agree with testing curves and the method is reasonable and effective.
基金Projects 50674085 supported by the Qing Lan Project of Jiangsu Provicne50774077 by the National Natural Science Foundation of China
文摘Excavation-and-support induced disturbances are likely to make water-enriched roofs to become weathered and fractured.The development and connection of cracks provide new water channels which may result in water loss,seriously affecting the in-tegrity and stability of roofs,leading to incidents of roof fall.Control of water-enriched rocks surrounding coal drifts is quite diffi-cult in China.Based on the practical situation of a water-enriched roof of a coal drift in working face 112201 of the Meihuajing coal mine,we studied the deformation features of surrounding rocks and the development of fractured areas and analyzed the major reasons for the decrease in load-carrying capacity,indicating that the key to maintain roof stability of this kind of coal drift is water retention.In addition,we proposed a staged control technology consisting of:1) surface grouting;2) cable anchor strengthening and 3) roof grouting,which has proven to be successful in this practical application.Our study indicates that,after the problem of water loss from the water-enriched roof had been effectively solved,a combined support system with high performance bolts can maintain the stability of the bearing structure,resulting in the control of roof stability in this kind of coal drift.
文摘This paper deals with the operation and performance of VSC （voltage source converter） based HVDC （high voltage direct current） interconnecting two extremely weak AC networks, the experience of Caprivilink project. It is shown in the paper that the HVDC converter automatically provides the supreme voltage and frequency stabilizing function when a critical situation is detected, no matter the disturbances appeared in sending end or receiving end AC networks. This supreme voltage and frequency stabilizing function makes it possible to avoid the blackout even if all the generators are tripped under an extra-ordinary worst contingency. By plots of recorded transients, the paper will show how the eventual blackouts are avoided.
文摘Transport risk assessment for the environment has two important aspects--problem solving model and solution veracity. Problem solving model is larger understanding of tasks interconnection, which represents in itself partial solution of general risk assessment. Veracity of solution means how the results are consistent with the reality. By researching of both aspects, it rises many unanswered questions. It is concerned about verification and validation of risk assessment results. By risk assessment for the environment it is possible to meet wide variety of more or less good soluble problems. It exists simple problems based on risk assessment of common traffic accidents connected with service charge outflow. On the other site, it exists complex problems of risk assessment connected with dangerous goods transport by traffic or pipelines. By simple problems solving there are not many questions about risk assessment veracity. It is possible to determine traffic accidents frequencies and service charge outflows consequences on the basis of examined events in transportation with great veracity. By complex problems the situation is quite different. The frequencies of large accidents are very low but the consequences for the environment may be large. Both are encumbered by large level of uncertainty. That is why the question is rising. To what degree, it is in these cases correct to make decision based on risk assessment.
文摘Hoffa fracture associated with ipsilateral femoral shaft fracture is very rare. Three cases of this rare type of injury were retrospectively reviewed. The sites of femoral shaft fractures and Hoffa fractures were documented. All femoral shall fractures were managed with internal tixation. The rate ofmisdiagnosis for the Hoffa fractures was documented. Functions of the affected knees were evaluated according to the modified Hospital for Special Surgery （HSS） scores at two years follow-up. Femoral fractures were either transverse or composite in all three cases. Ipsilateral Hoffa fractures occurred at medial condyle in two cases, and lateral condyle in one case. Only one Hoffa fracture was identified preoperatively. All the femoral shaft fiattures healed uneventfully. In the patient whose Hoffa fracture was correctly diagnosed, the modified HSS score was 94. In another patient, whose Hoffa fracture was treated by a second operation, the modified HSS score was 93. And in the third case, who refused additional operation for the Hoffa fracture, the modified HSS score was only 70. Conclusively femoral shall fracture can be associated with ipsilateral Hoffa fracture, especially in motorcycle accident. This type of iniury is very rare and misdiagnosis is common.
