The present status of self-elevating drilling units was analysed. Based on statistics of the main dimensions of self-elevating drilling units, a mathematical model was established using stepwise return procedures and ...The present status of self-elevating drilling units was analysed. Based on statistics of the main dimensions of self-elevating drilling units, a mathematical model was established using stepwise return procedures and a back-propagation neural network. mathematical model is applicable and reliable. The of the main dimensions of self-elevating drilling Analysis of examples of calculations showed that the model is useful for mastering the essential variations units and can be used for technical and economic analysis as well as in conceptual designs of drilling units.展开更多
In the process of designing self-elevating drilling unit, it is important, yet complicated, to use comparison and filtering to select the optimum scheme from the feasible ones. In this research, an index system and me...In the process of designing self-elevating drilling unit, it is important, yet complicated, to use comparison and filtering to select the optimum scheme from the feasible ones. In this research, an index system and methodology for the evaluation of self-elevating drilling unit was proposed. Based on this, a multi-objective combinatorial optimization model was developed, using the improved grey relation Analysis （GRA）, in which the analytic hierarchy process （AHP） was used to determine the weights of the evaluating indices. It considered the connections within the indices, reflecting the objective nature of things, and also considered the subjective interests of ship owners and the needs of designers. The evaluation index system and evaluation method can be used in the selection of an optimal scheme and advanced assessment. A case study shows the index system and evaluation method are scientific, reasonable, and easy to put into practice. At the same time, such an evaluation index system and evaluation method will be helpful for making decisions for other mobile platforms.展开更多
Since a self-elevating platform often works in water for a long time, the lattice leg is largely influenced by wave and current. The amplitude of leg joint stresses is a very important factor for the fatigue life of t...Since a self-elevating platform often works in water for a long time, the lattice leg is largely influenced by wave and current. The amplitude of leg joint stresses is a very important factor for the fatigue life of the platform. However, there are not many researches having been done on the mechanism and dynamic stress analysis of these leg joints. This paper focuses on the dynamic stress analysis and suppression methods of the leg joints of self-elevating platforms. Firstly, the dynamic stresses of the lattice leg joints are analyzed for a self-elevating platform by use of the 5th-order Stokes wave theory. Secondly, the axial and bending stresses are studied due to their large contributions to total stresses. And then, different joint types are considered and the leg-hull interface stiffness is analyzed for the improvement of the joint dynamic stress amplitude. Finally, some useful conclusions are drawn for the optimization design of the self-elevating platform.展开更多
无线信道建模对于理解、设计和优化无线通信系统具有重要意义,是无线通信领域中不可或缺的一部分。为了满足车联网(vehicle to everything,V2X)环境中的通信需求,研究空间中障碍物的分布对信道衰落特性的影响,本文提出了一种新的随机散...无线信道建模对于理解、设计和优化无线通信系统具有重要意义,是无线通信领域中不可或缺的一部分。为了满足车联网(vehicle to everything,V2X)环境中的通信需求,研究空间中障碍物的分布对信道衰落特性的影响,本文提出了一种新的随机散射簇生成算法,即通过把Matérn硬核点过程和泊松簇过程相结合来模拟真实V2X信道中的障碍物。在算法中,依据真实环境障碍物的方位设置散射簇的坐标位置,根据周围障碍物密度合理设置簇内散射点数量。利用传播图论进行仿真,考虑直射路径和单跳散射路径,基于信道冲激响应(channel impulse response,CIR)分别研究了功率延迟分布(power delay profile,PDP)和多普勒功率谱密度(Doppler power spectrum density,DPSD),并分析了不同移动轨迹下的均方根(root mean square,RMS)时延扩展的累计分布函数(cumulative distribution function,CDF),以及莱斯K因子的分布特性和角度功率谱(power angular spectrum,PAS)的分布。本文研究验证得到,所提出的模型有助于分析车辆-基础设施(vehicle to infrastructure,V2I)通信场景下的时域非平稳特性,为V2X通信系统的设计和优化提供了重要参考。展开更多
Wenlan FENG,Pierre MARIOTTE,Jun GU,XiaodongSONG,JinlingYANG,Fei YANG,Yuguo ZHAOand Ganlin ZHANG In the fourth and fifth lines of the study area section on Page 903,the mean annual temperature(MAT)and precipitation(MAP...Wenlan FENG,Pierre MARIOTTE,Jun GU,XiaodongSONG,JinlingYANG,Fei YANG,Yuguo ZHAOand Ganlin ZHANG In the fourth and fifth lines of the study area section on Page 903,the mean annual temperature(MAT)and precipitation(MAP)values are incorrect.They should be—17 to 24.2°C and 18.3 to 3155 mm,respectively.展开更多
The underhand cut-and-fill mining method is widely employed in underground mines,especially when the quality of surrounding rock mass or ore body is inferior or subjected to high stresses.Such a method typically requi...The underhand cut-and-fill mining method is widely employed in underground mines,especially when the quality of surrounding rock mass or ore body is inferior or subjected to high stresses.Such a method typically requires the construction of sill mats with cemented backfill to provide operators with safe artificial roofs.Accurate estimation of the minimum required strength of the sill mat is crucial to minimize binder consumption and ensure its stability upon base exposure.Over the years,only a few publications were devoted to determining the minimum required cohesion(cmin)of sill mats.None of them considered rock wall closure to be associated with the creep of surrounding rock mass.Moreover,the effect of rock wall closure associated with rock creep on the cminof the sill mat remains unknown.Thus,a series of numerical simulations was performed to fill this gap.The influence of rock creep on the cminof base-exposed sill mat was investigated for the first time.The numerical results indicate that Mitchell’s models could be suitable for sill mats subjected to negligible wall closure.However,this scenario is rare,especially when mine depth is large.In general,the cminof sill mats increases as mine depth increases.Neglecting rock creep would significantly underestimate the cminof sill mats.When mine depth is large and the rock mass exhibits severe creep,cemented backfill with ductile behavior(i.e.,with low stiffness but enough strength)should be considered to reduce binder consumption and prevent crushing failure.In all cases,promptly filling the mined-out stope below the sill mat can improve its stability and reduce its cminvalue.展开更多
冠突散囊菌(Eurotium cristatum)闭囊壳的产生和数量受各种与有性产孢相关的基因控制,而MAT基因(Mating type gene,MAT)是其中的关键基因之一,为调查MAT基因在冠突散囊菌不同发育阶段的表达量变化,应用实时荧光定量PCR技术对该菌的营养...冠突散囊菌(Eurotium cristatum)闭囊壳的产生和数量受各种与有性产孢相关的基因控制,而MAT基因(Mating type gene,MAT)是其中的关键基因之一,为调查MAT基因在冠突散囊菌不同发育阶段的表达量变化,应用实时荧光定量PCR技术对该菌的营养生长时期、无性产孢时期和有性产孢时期3个阶段的MAT基因表达量进行检测。结果显示:以营养生长时期为对照,在有性产孢时期MAT1-1-1基因上调31.12倍,MAT1-2-1基因上调5.87倍;在无性产孢时期MAT1-1-1基因上调4.25倍,MAT1-2-1基因仅为对照的0.03倍。表明,MAT基因与冠突散囊菌的有性产孢相关,其中MAT1-1-1基因还可能与无性产孢相关。展开更多
基金Supported by the National 863 Plan Foundation under Grant No.2003AA414060
文摘The present status of self-elevating drilling units was analysed. Based on statistics of the main dimensions of self-elevating drilling units, a mathematical model was established using stepwise return procedures and a back-propagation neural network. mathematical model is applicable and reliable. The of the main dimensions of self-elevating drilling Analysis of examples of calculations showed that the model is useful for mastering the essential variations units and can be used for technical and economic analysis as well as in conceptual designs of drilling units.
基金Supported by the National 863 Plan Foundation under Grant No.2003AA414060
文摘In the process of designing self-elevating drilling unit, it is important, yet complicated, to use comparison and filtering to select the optimum scheme from the feasible ones. In this research, an index system and methodology for the evaluation of self-elevating drilling unit was proposed. Based on this, a multi-objective combinatorial optimization model was developed, using the improved grey relation Analysis （GRA）, in which the analytic hierarchy process （AHP） was used to determine the weights of the evaluating indices. It considered the connections within the indices, reflecting the objective nature of things, and also considered the subjective interests of ship owners and the needs of designers. The evaluation index system and evaluation method can be used in the selection of an optimal scheme and advanced assessment. A case study shows the index system and evaluation method are scientific, reasonable, and easy to put into practice. At the same time, such an evaluation index system and evaluation method will be helpful for making decisions for other mobile platforms.
基金supported by the Shanghai Science Foundation of Important Projects for Post Doctoral Research, China (Grant No. 09R21421600)
文摘Since a self-elevating platform often works in water for a long time, the lattice leg is largely influenced by wave and current. The amplitude of leg joint stresses is a very important factor for the fatigue life of the platform. However, there are not many researches having been done on the mechanism and dynamic stress analysis of these leg joints. This paper focuses on the dynamic stress analysis and suppression methods of the leg joints of self-elevating platforms. Firstly, the dynamic stresses of the lattice leg joints are analyzed for a self-elevating platform by use of the 5th-order Stokes wave theory. Secondly, the axial and bending stresses are studied due to their large contributions to total stresses. And then, different joint types are considered and the leg-hull interface stiffness is analyzed for the improvement of the joint dynamic stress amplitude. Finally, some useful conclusions are drawn for the optimization design of the self-elevating platform.
文摘无线信道建模对于理解、设计和优化无线通信系统具有重要意义,是无线通信领域中不可或缺的一部分。为了满足车联网(vehicle to everything,V2X)环境中的通信需求,研究空间中障碍物的分布对信道衰落特性的影响,本文提出了一种新的随机散射簇生成算法,即通过把Matérn硬核点过程和泊松簇过程相结合来模拟真实V2X信道中的障碍物。在算法中,依据真实环境障碍物的方位设置散射簇的坐标位置,根据周围障碍物密度合理设置簇内散射点数量。利用传播图论进行仿真,考虑直射路径和单跳散射路径,基于信道冲激响应(channel impulse response,CIR)分别研究了功率延迟分布(power delay profile,PDP)和多普勒功率谱密度(Doppler power spectrum density,DPSD),并分析了不同移动轨迹下的均方根(root mean square,RMS)时延扩展的累计分布函数(cumulative distribution function,CDF),以及莱斯K因子的分布特性和角度功率谱(power angular spectrum,PAS)的分布。本文研究验证得到,所提出的模型有助于分析车辆-基础设施(vehicle to infrastructure,V2I)通信场景下的时域非平稳特性,为V2X通信系统的设计和优化提供了重要参考。
文摘Wenlan FENG,Pierre MARIOTTE,Jun GU,XiaodongSONG,JinlingYANG,Fei YANG,Yuguo ZHAOand Ganlin ZHANG In the fourth and fifth lines of the study area section on Page 903,the mean annual temperature(MAT)and precipitation(MAP)values are incorrect.They should be—17 to 24.2°C and 18.3 to 3155 mm,respectively.
基金financially supported by the Project of National Key Research and Development Program of China(No.2022YFE0129200)the Beijing Nova Program(No.20220484057)+3 种基金the China Scholarship Council(No.202010300001)the National Natural Science Foundation of China(No.52304101)financial support from the Natural Sciences and Engineering Research Council of Canada(No.RGPIN-201806902)industrial partners of the Research Institute on Mines and the Environment(No.RIME UQAT-Polytechnique)。
文摘The underhand cut-and-fill mining method is widely employed in underground mines,especially when the quality of surrounding rock mass or ore body is inferior or subjected to high stresses.Such a method typically requires the construction of sill mats with cemented backfill to provide operators with safe artificial roofs.Accurate estimation of the minimum required strength of the sill mat is crucial to minimize binder consumption and ensure its stability upon base exposure.Over the years,only a few publications were devoted to determining the minimum required cohesion(cmin)of sill mats.None of them considered rock wall closure to be associated with the creep of surrounding rock mass.Moreover,the effect of rock wall closure associated with rock creep on the cminof the sill mat remains unknown.Thus,a series of numerical simulations was performed to fill this gap.The influence of rock creep on the cminof base-exposed sill mat was investigated for the first time.The numerical results indicate that Mitchell’s models could be suitable for sill mats subjected to negligible wall closure.However,this scenario is rare,especially when mine depth is large.In general,the cminof sill mats increases as mine depth increases.Neglecting rock creep would significantly underestimate the cminof sill mats.When mine depth is large and the rock mass exhibits severe creep,cemented backfill with ductile behavior(i.e.,with low stiffness but enough strength)should be considered to reduce binder consumption and prevent crushing failure.In all cases,promptly filling the mined-out stope below the sill mat can improve its stability and reduce its cminvalue.
文摘冠突散囊菌(Eurotium cristatum)闭囊壳的产生和数量受各种与有性产孢相关的基因控制,而MAT基因(Mating type gene,MAT)是其中的关键基因之一,为调查MAT基因在冠突散囊菌不同发育阶段的表达量变化,应用实时荧光定量PCR技术对该菌的营养生长时期、无性产孢时期和有性产孢时期3个阶段的MAT基因表达量进行检测。结果显示:以营养生长时期为对照,在有性产孢时期MAT1-1-1基因上调31.12倍,MAT1-2-1基因上调5.87倍;在无性产孢时期MAT1-1-1基因上调4.25倍,MAT1-2-1基因仅为对照的0.03倍。表明,MAT基因与冠突散囊菌的有性产孢相关,其中MAT1-1-1基因还可能与无性产孢相关。
