Different geophysical exploration methods have significant differences in terms of exploration depth,especially in frequency domain electromagnetic(EM)exploration.According to the definition of skin depth,this differe...Different geophysical exploration methods have significant differences in terms of exploration depth,especially in frequency domain electromagnetic(EM)exploration.According to the definition of skin depth,this difference will increase with the effective detection frequency of the method.As a result,when performing three-dimensional inversion on single type of EM data,it is not possible to effectively distinguish the subsurface geoelectric structure at the full scale.Therefore,it is necessary to perform joint inversion on different type of EM data.In this paper we combine the magnetotelluric method(MT)with the controlled-source audio-magnetotelluric method(CSAMT)to study the frequency-domain three-dimensional(3D)joint inversions,and we use the unstructured finite-element method to do the forward modeling for them,so that the numerical simulation accuracies of different electromagnetic methods can be satisfied.By combining the two sets of data,we can obtain the sensitivity of the electrical structure at different depths,and depict the full-scale subsurface geoelectric structures.In actual mineral exploration,the 3D joint inversion is more useful for identifying subsurface veins in the shallow part and blind mines in the deep part.It can delineate the morphological distribution of ore bodies more completely and provide reliable EM interpretations to guide the mining of minerals.展开更多
The existence of the relative radial and axial movements of a revolute joint’s journal and bearing is widely known.The three-dimensional(3D)revolute joint model considers relative radial and axial clearances;therefor...The existence of the relative radial and axial movements of a revolute joint’s journal and bearing is widely known.The three-dimensional(3D)revolute joint model considers relative radial and axial clearances;therefore,the freedoms of motion and contact scenarios are more realistic than those of the two-dimensional model.This paper proposes a wear model that integrates the modeling of a 3D revolute clearance joint and the contact force and wear depth calculations.Time-varying contact stiffness is first considered in the contact force model.Also,a cycle-update wear depth calculation strategy is presented.A digital image correlation(DIC)non-contact measurement and a cylindricity test are conducted.The measurement results are compared with the numerical simulation,and the proposed model’s correctness and the wear depth calculation strategy are verified.The results show that the wear amount distribution on the bearing’s inner surface is uneven in the axial and radial directions due to the journal’s stochastic oscillations.The maximum wear depth locates where at the bearing’s edges the motion direction of the follower shifts.These find-ings help to seek the revolute joints’wear-prone parts and enhance their durability and reliability through improved design.展开更多
Ultra-high molecular weight polyethylene（UHMWPE） fiber/epoxy composites were fabricated by a vacuum assisted resin infused（VARI） processing technology. The curing condition of composites was at a cure temperature ...Ultra-high molecular weight polyethylene（UHMWPE） fiber/epoxy composites were fabricated by a vacuum assisted resin infused（VARI） processing technology. The curing condition of composites was at a cure temperature of 80 ℃ for 3h in a drying oven. The characteristics of 2.5D（shallow bend-joint and deep straight-joint） structure and 3D orthogonal structure were compared. The failure behavior, flexural strength, and microstructures of both composites were investigated. It was found that the flexural property was closely related to undulation angle θ. The flexural strength of 3D orthogonal structure composite was superior to the other two structures composites with the same weave parameters and resin.展开更多
目的基于后交叉韧带(posterior cruciate ligament,PCL)3D模型技术建立低位胫骨隧道并测量其解剖参数。方法选取101例健康膝关节CT影像资料,利用Mimics21.0(Materialise,比利时)软件建立PCL 3D虚拟手术模型并建立前内侧与前外侧入路的...目的基于后交叉韧带(posterior cruciate ligament,PCL)3D模型技术建立低位胫骨隧道并测量其解剖参数。方法选取101例健康膝关节CT影像资料,利用Mimics21.0(Materialise,比利时)软件建立PCL 3D虚拟手术模型并建立前内侧与前外侧入路的低位胫骨隧道,测量胫骨隧道长度(length of the PCL tibial tunnel,LTT),胫骨隧道与胫骨平台3D夹角(3D included angle between tibial medial axis extension line and tibial plateau,3D ATPT)以及隧道入口点到胫骨平台距离(perpendicular distance of the tunnel’s entry point to the tibial plateau,PTT)。利用SPSS 25.0进行统计学分析。结果前内侧与前外侧胫骨隧道参数测量,LTT分别为(45.56±4.27)mm、(43.93±4.10)mm,差异有统计学意义(P<0.05);3D ATPT分别为(48.17±6.12)°、(54.49±5.81)°,差异有统计学意义(P<0.05);PTT分别为(61.86±6.80)mm、(63.51±6.32)mm,差异有统计学意义(P<0.05)。结论测量PCL的3D模型低位胫骨隧道相关参数,可为临床PCL重建手术提供理论参考。展开更多
目的:研究MRI 3D CUBE T_(2)序列检查在踝关节外伤患者韧带损伤诊断中的价值。方法:选择2020年4月—2023年4月于白银市第一人民医院就诊的226例踝关节外伤拟行手术术前患者作为研究对象,按照不同检查方式将患者分为观察组(n=126)与对照...目的:研究MRI 3D CUBE T_(2)序列检查在踝关节外伤患者韧带损伤诊断中的价值。方法:选择2020年4月—2023年4月于白银市第一人民医院就诊的226例踝关节外伤拟行手术术前患者作为研究对象,按照不同检查方式将患者分为观察组(n=126)与对照组(n=100)。观察组采用MRI 3D CUBE T_(2)序列检查,对照组采取常规MRI检查。比较两组患侧、健侧距腓前韧带测量结果、诊断效能。结果:两组患侧、健侧距腓前韧带宽度及厚度比较,差异无统计学意义(P>0.05)。观察组Ⅰ级踝关节外伤患者韧带损伤诊断准确度、敏感度、特异度、阳性预测值、阴性预测值高于对照组,Ⅱ级患者准确度、敏感度、阴性预测值高于对照组,Ⅲ级患者准确度、特异度、阳性预测值高于对照组,差异有统计学意义(P<0.05)。结论:MRI 3D CUBE T_(2)序列检查踝关节外伤患者韧带损伤诊断效能高于常规MRI检查,可作为治疗效果评价及康复治疗的重要依据。展开更多
基金Supported by the National Natural Science Foundation of China(No.42074120).
文摘Different geophysical exploration methods have significant differences in terms of exploration depth,especially in frequency domain electromagnetic(EM)exploration.According to the definition of skin depth,this difference will increase with the effective detection frequency of the method.As a result,when performing three-dimensional inversion on single type of EM data,it is not possible to effectively distinguish the subsurface geoelectric structure at the full scale.Therefore,it is necessary to perform joint inversion on different type of EM data.In this paper we combine the magnetotelluric method(MT)with the controlled-source audio-magnetotelluric method(CSAMT)to study the frequency-domain three-dimensional(3D)joint inversions,and we use the unstructured finite-element method to do the forward modeling for them,so that the numerical simulation accuracies of different electromagnetic methods can be satisfied.By combining the two sets of data,we can obtain the sensitivity of the electrical structure at different depths,and depict the full-scale subsurface geoelectric structures.In actual mineral exploration,the 3D joint inversion is more useful for identifying subsurface veins in the shallow part and blind mines in the deep part.It can delineate the morphological distribution of ore bodies more completely and provide reliable EM interpretations to guide the mining of minerals.
文摘The existence of the relative radial and axial movements of a revolute joint’s journal and bearing is widely known.The three-dimensional(3D)revolute joint model considers relative radial and axial clearances;therefore,the freedoms of motion and contact scenarios are more realistic than those of the two-dimensional model.This paper proposes a wear model that integrates the modeling of a 3D revolute clearance joint and the contact force and wear depth calculations.Time-varying contact stiffness is first considered in the contact force model.Also,a cycle-update wear depth calculation strategy is presented.A digital image correlation(DIC)non-contact measurement and a cylindricity test are conducted.The measurement results are compared with the numerical simulation,and the proposed model’s correctness and the wear depth calculation strategy are verified.The results show that the wear amount distribution on the bearing’s inner surface is uneven in the axial and radial directions due to the journal’s stochastic oscillations.The maximum wear depth locates where at the bearing’s edges the motion direction of the follower shifts.These find-ings help to seek the revolute joints’wear-prone parts and enhance their durability and reliability through improved design.
文摘目的 评价磁共振3D space序列在膝关节半月板放射状撕裂中的诊断价值,提高对此病的影像认识,为临床诊疗提供帮助。方法 回顾性分析29例经关节镜证实的膝关节半月板放射状撕裂患者的磁共振资料;对比常规磁共振2D序列与3D space序列在半月板放射状撕裂病变中的诊断效能,使用Fisher确切概率法对两种方法诊断半月板放射状撕裂的准确率进行比较。结果 3D space序列和常规2D序列诊断半月板放射状撕裂的准确率分别为96.7%(29/30)、80.0%(24/30),3D space序列诊断准确率高于常规2D序列,差异有统计学意义(P<0.05)。结论 3D space序列在半月板放射状撕裂的诊断中具有较高价值,其诊断效能优于2D序列。
基金Funded by the National Natural Science Foundation of China(No.51001117)
文摘Ultra-high molecular weight polyethylene（UHMWPE） fiber/epoxy composites were fabricated by a vacuum assisted resin infused（VARI） processing technology. The curing condition of composites was at a cure temperature of 80 ℃ for 3h in a drying oven. The characteristics of 2.5D（shallow bend-joint and deep straight-joint） structure and 3D orthogonal structure were compared. The failure behavior, flexural strength, and microstructures of both composites were investigated. It was found that the flexural property was closely related to undulation angle θ. The flexural strength of 3D orthogonal structure composite was superior to the other two structures composites with the same weave parameters and resin.
文摘目的基于后交叉韧带(posterior cruciate ligament,PCL)3D模型技术建立低位胫骨隧道并测量其解剖参数。方法选取101例健康膝关节CT影像资料,利用Mimics21.0(Materialise,比利时)软件建立PCL 3D虚拟手术模型并建立前内侧与前外侧入路的低位胫骨隧道,测量胫骨隧道长度(length of the PCL tibial tunnel,LTT),胫骨隧道与胫骨平台3D夹角(3D included angle between tibial medial axis extension line and tibial plateau,3D ATPT)以及隧道入口点到胫骨平台距离(perpendicular distance of the tunnel’s entry point to the tibial plateau,PTT)。利用SPSS 25.0进行统计学分析。结果前内侧与前外侧胫骨隧道参数测量,LTT分别为(45.56±4.27)mm、(43.93±4.10)mm,差异有统计学意义(P<0.05);3D ATPT分别为(48.17±6.12)°、(54.49±5.81)°,差异有统计学意义(P<0.05);PTT分别为(61.86±6.80)mm、(63.51±6.32)mm,差异有统计学意义(P<0.05)。结论测量PCL的3D模型低位胫骨隧道相关参数,可为临床PCL重建手术提供理论参考。
文摘目的:研究MRI 3D CUBE T_(2)序列检查在踝关节外伤患者韧带损伤诊断中的价值。方法:选择2020年4月—2023年4月于白银市第一人民医院就诊的226例踝关节外伤拟行手术术前患者作为研究对象,按照不同检查方式将患者分为观察组(n=126)与对照组(n=100)。观察组采用MRI 3D CUBE T_(2)序列检查,对照组采取常规MRI检查。比较两组患侧、健侧距腓前韧带测量结果、诊断效能。结果:两组患侧、健侧距腓前韧带宽度及厚度比较,差异无统计学意义(P>0.05)。观察组Ⅰ级踝关节外伤患者韧带损伤诊断准确度、敏感度、特异度、阳性预测值、阴性预测值高于对照组,Ⅱ级患者准确度、敏感度、阴性预测值高于对照组,Ⅲ级患者准确度、特异度、阳性预测值高于对照组,差异有统计学意义(P<0.05)。结论:MRI 3D CUBE T_(2)序列检查踝关节外伤患者韧带损伤诊断效能高于常规MRI检查,可作为治疗效果评价及康复治疗的重要依据。
文摘针对无线信号易受信道影响的难题,将智能反射面(Intelligent Reflecting Surface,IRS)被动波束赋形和基站(Base Station,BS)3D波束赋形进行联合设计。为最大化加权和速率,首先基于投影梯度下降法和加权均方误差等效原理,提出了一种多用户交替优化算法(Multi-User Alternative Optimization,MU-AO),其具有普适性。其次,基于高信噪比(Signal-to-Noise Ratio,SNR)近似原理,提出了一种多用户三级优化算法(Multi-User Three Stage Optimization,MUTSO),通过计算次优组合解来降低计算复杂度。最后,基于BS天线下倾角预定义策略,提出了一种多用户基于直射链路优化算法(Multi-User Direct-Link Based Optimization,MU-DLBO),能够实现复杂度与性能的均衡。实验表明,所提算法均能有效提升系统加权和速率,体现了联合波束赋形的有效性。
