多模态影像学检查在诊断早期强直性脊柱炎骶髂关节疾病中的效果

目的:探究在早期强直性脊柱炎骶髂关节疾病诊断中不同放射影像学检查方法的应用效果。方法:抽取2018年5月-2020年1月本院收治的早期强直性脊柱炎骶髂关节疾病患者65例作为研究对象,所有患者均开展X线、CT、MRI影像学检查,对比三种不同影像学检查方法的检出率、影像学特征。结果:X线、CT、MRI检出率分别为38.46%(25/65)、60.00%(39/65)、76.92%(50/65),检出率相比,MRI、CT明显高于X线,P<0.05;X线、CT、MRI影像学特征,发现关节间隙出现不同的异常,如关节面出现侵蚀、骨质囊变现象,关节面下骨质出现硬化与关节软骨出现肿胀,其中MRI、CT检查,阳性率高于X线,P<0.05。而对于软组织肿胀、骨髓水肿、滑膜炎症、关节滑膜增厚等现象,只能通过MRI检查才能诊断。结论:在早期强直性脊柱炎骶髂关节疾病诊断中,X线、CT、MRI影像学检查均具有一定的指导意义,而MRI不仅可以提高检出率,还能准确反映微小病灶及其软组织病变,对于早期发现骶髂关节炎值得推荐。     

Inconel 690传热管GTAW对接焊接头组织及力学性能研究

对Inconel 690传热管材进行钨极气体保护焊(GTAW)对接焊,采用拉伸试验机、压扁试验机和光学显微镜测试和分析传热管焊接接头,同时利用ANSYS软件开展焊接接头在设计工况失压时的一次应力强度校核。研究结果表明:焊缝中心为树枝胞状晶,熔合线附近为粗大柱状晶。室温时接头的平均抗拉强度为619 MPa,平均屈服强度为292 MPa,350℃时接头平均抗拉强度为475 MPa,平均屈服强度为206 MPa,拉伸接头断裂从熔合区开始贯穿整个焊缝组织,呈塑性断裂。压扁试验和反向压扁试验结果表明管接头完好。通过ANSYS分析可知,设计工况下传热管接头350℃许用应力强度150 MPa限值可满足其一次应力强度要求,且裕量较大。     

高应力软岩巷道锚注一体化联合支护技术应用

介绍了国家专利注锚剂、中空注浆锚索等产品,以国家能源麦朵山煤矿11采区2煤辅助运输巷为研究对象,采用数值模拟、理论分析、现场测试及井下试验相结合的综合研究方法,对11采区2煤辅助运输巷采用锚注一体联合支护技术,来实现对岩体裂隙注浆,使浆料与岩体结为一体,在围岩与支护体共同作用过程中,实现强岩增荷的作用,维护巷道的稳定性,实现工作面的安全生产。     

智能假肢膝关节的研发要点及其研究进展综述

目的 介绍国内外智能假肢膝关节研究的主要进展,为相关领域的研发提供可借鉴的思路.方法 基于机械结构、调控方式、驱动方式,对典型假肢膝关节进行了分类比较,并从假肢穿戴者的运动意图识别、驱动控制、人机协调控制等方面做了分析.此外,对假肢膝关节在智能化研究与安全性、个性化与通用性、人机共融技术、科学伦理、关键技术等方面需要注意的问题,提出了研发要点和技术思路.结论 智能假肢膝关节应注重安全性与稳定性,规避用户在使用过程中的潜在危险因素;实现假肢控制参数的自整定和灵活适配,在个性化与通用性上达到平衡;综合考虑人—机—环境因素,实现协调控制;坚持"以人为本",在技术方法和科学伦理两个方面开展医工结合的研究;突破关键技术限制,建立完善的社会医疗康复保障服务体系.     

Stress wave propagation in adhesively bonded functionally graded cylinders: an improved model

This study presents an improved mathematical model to analyse the stress wave propagation in adhesively bonded functionally graded (FG) circular cylinders (butt joint) under an axial impulsive load. The volume fractions of the material constituents in the upper and lower cylinders were functionally tailored through the thickness of each cylinder using a power-law. The effective material properties of both cylinders, which are made of aluminum (Al) and silicon carbide (SiC), at any point were predicted by using the Mori–Tanaka homogenization scheme. In this improved model, the governing equations of the wave propagation include the spatial derivatives of local mechanical properties and were discretized by means of the finite difference method. The influence of these spatial derivatives and the compositional gradient exponent on the displacement and stress distributions of the joint was investigated. The material composition variations of both cylinders affected the displacement and stress fields whereas the compositional gradient exponent had a minor effect. The stress concentrations were alleviated in time, the displacement and stress distributions/variations around/along the upper and lower cylinder-adhesive interfaces were significantly affected by the adhesive layer. The spatial derivatives also affected the temporal histories of the displacement and stress components evaluated at the selected critical points of the upper cylinder, adhesive layer and lower cylinder. The consideration of the spatial local material derivatives provided a more accurate mathematical model of wave propagations through the graded layered structures.     

New insights into microstructural changes during transient liquid phase bonding of GTD-111 superalloy

The effects of joining temperature (T_J) and time (t_J) on microstructure of the transient liquid phase (TLP) bonding of GTD-111 superalloy were investigated. The bonding process was applied using BNi-3 filler at temperatures of 1080, 1120, and 1160 °C for isothermal solidification time of 195, 135, and 90 min, respectively. Homogenization heat treatment was also applied to all of the joints. The results show that intermetallic and eutectic compounds such as Ni-rich borides, Ni−B−Si ternary compound and eutectic-γ continuously are formed in the joint region during cooling. By increasing t_J, intermetallic phases are firstly reduced and eventually eliminated and isothermal solidification is completed as well. With the increase of the holding time at all of the three bonding temperatures, the thickness of the athermally solidified zone (ASZ) and the volume fraction of precipitates in the bonding area decrease and the width of the diffusion affected zone (DAZ) increases. Similar results are also obtained by increasing T_J from 1080 to 1160 °C at t_J=90 min. Furthermore, increasing the T_J from 1080 to 1160 °C leads to the faster elimination of intermetallic phases from the ASZ. However, these phases are again observed in the joint region at 1180 °C. It is observed that by increasing the bonding temperature, the bonding width and the rate of dissolution of the base metal increase. Based on these results, increasing the homogenization time from 180 to 300 min leads to the elimination of boride precipitates in the DAZ and a high uniformity of the concentration of alloying elements in the joint region and the base metal.     

奥钢联板坯铸机驱动力报警问题的分析及改进

浇铸过程中，驱动力报警会导致紧急停浇甚至滞坯事故发生。为防止事故发生，通常采用降速、强冷等措施，但降速造成成本浪费，强冷又产生裂纹等质量缺陷，两者都难以满足生产需要。通过对铸机的各项参数对比分析，找到影响驱动力报警的主要原因为辊缝异常，轻压下模型参数、冷却工艺设置不合理等，通过调整二冷工艺、优化模型参数、加强轻压下区域扇形段辊缝维护，可以达到明显降低驱动力、消除报警的目的，从而保证连铸生产稳定。     

超深高温高压气井完井含伸缩管测试管柱的应力与变形特征

塔里木盆地MJ4井测试管柱长6 617 m,测试时井底压力为101.63 MPa,完井作业过程中管柱出现了塑性变形问题,迫切需要准确地确定管柱塑性变形究竟发生在完井作业的哪个阶段。为此,采用三维有限元分析方法,结合MJ4井坐封、压裂和试油3个典型的载荷工况,对管柱的变形和轴向应力分布进行了数值计算,总结了含伸缩管的完井测试管柱力学行为计算流程。研究内容主要包括:①提出了具有伸缩管的油管柱系统中伸缩管的伸长与闭合状态的判断依据,并给出了相应的计算原理和计算公式,计算了MJ4井油管柱伸缩管的伸长—闭合状态;②给出了水力锚咬合不良产生的封隔器环空附加压差载荷的分析计算方法,模拟了其对管柱系统变形行为的影响,指出了附加压差载荷对管柱的塑性屈曲变形有着重要的影响;③计算模型引入了侧向屈曲变形的限制,从而间接考虑了接箍刚度对屈曲变形的影响,计算分析了油管柱在各种载荷共同作用下的变形情况,得到的数值结果显示与观察到的变形现象相同。研究结果表明,MJ4井管柱的塑性变形发生在压裂改造施工阶段,各种形式的液体压力载荷及重力载荷是塑性变形的主要原因。结论认为,含伸缩管测试管柱的力学计算模型可作为优化施工和管柱系统结构设计的重要理论工具和分析手段。     

一种5G分布式联合传输策略研究

在5G超密集网络UDN部署的低功率节点覆盖下,小区覆盖重叠严重导致了小区间存在较大的同层干扰,由用户话务在时间和空间上分布不均匀而产生的小区负载不均衡造成了小区网络资源的严重浪费,小区用户体验大幅度降低。基于5G网络和TDD-CoMP技术的新特征,构建了一种以用户为中心的5G分布式联合传输模型,对模型中的干扰、功耗以及速率解决方案进行了分析,最后得出一种可有效降低系统能耗,提升用户整体的速率的5G分布式联合传输策略研究方案。