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
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
Pinus squamata X. W. Li, a recently-described species of the Pinaceae, is an extremely endangered pine with only 32 individuals in the wild. This species was thought to be intermediate between P. bungeana Zuec. ex End...Pinus squamata X. W. Li, a recently-described species of the Pinaceae, is an extremely endangered pine with only 32 individuals in the wild. This species was thought to be intermediate between P. bungeana Zuec. ex Endl. of subgen. Strobus and P. yunnanensis Franch. of subgen. Pinus by the original author. We made an effort to address the question of the phylogenetic relationship of this peculiar and important species in the context of the major groups of the genus Pinus by using sequences of the rbcL, matK,genes, rpl20-rps18 spacer, trnV intron of the chloroplast genome and the nuclear ribosomal ITS region. The results of the separated analysis and the combined analysis of the four cpDNA sequences and ITS sequence indicated that P. squamata was a stable member of subsect. Gerardianae and P. gerardiana Wall. was the closest species of P. squamata phylogenetically. As a result, the causes of the distribution pattern of subsect. Gerardianae were also discussed.展开更多
The yeast MATα1 is required for the activation of α-specific genes in Saccharomyces cerevisiae and thus confers the α-cell identity of the yeast. MATα1 contains a domain called the α-domain which has significant ...The yeast MATα1 is required for the activation of α-specific genes in Saccharomyces cerevisiae and thus confers the α-cell identity of the yeast. MATα1 contains a domain called the α-domain which has significant sequence identity to the HMG-box family of proteins. A multiple sequence alignment of several α-domains and various structurally determined HMG-box domains has revealed that both domains possess very similar structural and functional residues. We found that the basic amino acids of the N-terminal loop, the intercalating hydrophobic residues of the first helix, and the hydrophobic residues required for interactions within the core of the protein are remarkably conserved in α-domains and HMG-box proteins. Our generated molecular models suggest that the first and third helix will be shorter and that the HMG-box core is not an isolated domain. The region beyond the conserved HMG-box motif contains an extended helical region for about 20 - 30 amino acids. Structural models generated by comparative modeling and ab initio modeling reveal that this region will add two or more additional α-helices and will make significant contacts to helix III, II and I of the HMG-box core. We were able to illustrate how the extended α-domain would bind to DNA by merging of the α-domain and the LEF-1/DNA complex. The models we are reporting will be helpful in understanding how MATα1 binds to DNA with its partner MCM1 and activates transcription of α-specific genes. These models will also aid in future biophysical studies of MATα1 including the crystallization and structure determination.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
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。
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Pinus squamata X. W. Li, a recently-described species of the Pinaceae, is an extremely endangered pine with only 32 individuals in the wild. This species was thought to be intermediate between P. bungeana Zuec. ex Endl. of subgen. Strobus and P. yunnanensis Franch. of subgen. Pinus by the original author. We made an effort to address the question of the phylogenetic relationship of this peculiar and important species in the context of the major groups of the genus Pinus by using sequences of the rbcL, matK,genes, rpl20-rps18 spacer, trnV intron of the chloroplast genome and the nuclear ribosomal ITS region. The results of the separated analysis and the combined analysis of the four cpDNA sequences and ITS sequence indicated that P. squamata was a stable member of subsect. Gerardianae and P. gerardiana Wall. was the closest species of P. squamata phylogenetically. As a result, the causes of the distribution pattern of subsect. Gerardianae were also discussed.
文摘The yeast MATα1 is required for the activation of α-specific genes in Saccharomyces cerevisiae and thus confers the α-cell identity of the yeast. MATα1 contains a domain called the α-domain which has significant sequence identity to the HMG-box family of proteins. A multiple sequence alignment of several α-domains and various structurally determined HMG-box domains has revealed that both domains possess very similar structural and functional residues. We found that the basic amino acids of the N-terminal loop, the intercalating hydrophobic residues of the first helix, and the hydrophobic residues required for interactions within the core of the protein are remarkably conserved in α-domains and HMG-box proteins. Our generated molecular models suggest that the first and third helix will be shorter and that the HMG-box core is not an isolated domain. The region beyond the conserved HMG-box motif contains an extended helical region for about 20 - 30 amino acids. Structural models generated by comparative modeling and ab initio modeling reveal that this region will add two or more additional α-helices and will make significant contacts to helix III, II and I of the HMG-box core. We were able to illustrate how the extended α-domain would bind to DNA by merging of the α-domain and the LEF-1/DNA complex. The models we are reporting will be helpful in understanding how MATα1 binds to DNA with its partner MCM1 and activates transcription of α-specific genes. These models will also aid in future biophysical studies of MATα1 including the crystallization and structure determination.
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。
