双向循环荷载作用下砾石-格栅界面动力剪切特性

在动荷载作用下,加筋土结构中筋土界面不仅会受到水平循环剪切作用,还会受到循环荷载的压缩作用。采用大型直剪仪对双向循环作用筋土界面动力剪切特性进行研究,探究不同循环法向荷载频率、水平循环剪切频率和法向荷载波形对界面剪切强度的影响。结果表明:当循环法向荷载频率和水平循环剪切频率一致时,峰值剪切应力和最大竖向位移随着频率的增加而增加,前后半周期剪切应力和位移曲线时间差均相同;反之,滞回圈应力-位移关系和竖向位移会由于双向循环荷载频率的不同呈现两种不同形态特性;正弦波法向荷载作用下剪切应力和竖向位移最大,而斜波和方波荷载作用下,滞回圈和竖向位移变化曲线较三角波和正弦波差别较明显;剪切刚度随着双向循环荷载频率的增大而增大,正弦波作用下界面剪切刚度最大,斜波作用下界面剪切刚度最小。

考虑筋土界面软化的三明治形加筋土挡墙地震响应分析

三明治形加筋土挡墙作为一种新型的加筋土结构具有黏土的廉价、取材较方便、砂土界面剪切强度较高等优点。基于室内大型直剪仪研究了地震荷载作用下砂土与格栅界面的动力特性,通过回归分析得到了加筋土挡墙中筋土界面剪切刚度在动荷载作用下呈现剪切软化的变化规律经验公式;然后编制fish语言将该公式导入FLAC^3D软件中,建立了考虑筋土界面剪切刚度变化规律的三维计算模型,分析了加筋土挡墙的各种设计参数(挡墙的高度、筋材的长度、筋材的弹性模量、筋材的间距、面板的类型)对三明治形加筋土挡墙动力特性的影响。结果表明:加筋土挡墙的高度越高,面板的侧向位移越大;当峰值加速度为0.2 g(g为重力加速度)时,潜在破裂面交于墙顶接近0.36 H(H为挡土墙高),峰值加速度为0.4 g时,潜在破裂面交于墙顶接近0.47 H;筋材弹性模量的增大和筋材间距的减小能够增加挡墙的抗变形能力,且随着筋材长度的增加,面板最大水平位移逐渐减小;在两种峰值加速度下,模块式面板加筋土挡墙容易发生局部面板鼓胀破坏,而整体式面板加筋土挡墙容易发生整体倾倒破坏。

Enterprise innovation, corporate social responsibility and their interactive relationship: A review

Under the new normal economic growth, lack of motivation, structural imbalances in the economy, the shortage of resources, resource utilization inefficiency, environmental damage and other issues have become increasingly prominent, enterprises as the carrier of economy is one of the root of the problem. Research on enterprise innovation and corporate social responsibility issues, it is conducive to the development of enterprise itself and the transformation of Chinese economy. This paper reviewed the research status of relationships between innovation and corporate social responsibility, through comb the aspects of the definitions and evolution of enterprise innovation and social responsibility, also include both the relationship and the new way(responsible innovation) of combination of them, we found the presence of index system is not perfect, and lack of in-depth comprehensive study and opportunities for future research is prospected.

Influence of government subsidies on western enterprise technology innovation

With the deepening of the western development,supports of the country for the western region of China continued to increase.It also includes the support for enterprise innovation activities,by reducing the tax,exemption,subsidies and other means.Due to the effect of government subsidies on enterprise innovation activities is different in different regions,industries and so on,there is a big controversy.Therefore,we use the panel data of listed companies in manufacturing industry of western region as samples for empirical research,to research the effect of government subsidies on enterprise innovation activities in the western of China,the study found that overall,the current government subsidies has a positive effect on Enterprise R&D investment,whereas the last year's government subsidy has a negative effect on R&D investment,but it's incentive effect is greater than the crowding out effect.The study also found there are different effects between the state-owned enterprises and private enterprises,the crowding out effect of private enterprises is very small and not significant.

基于多任务学习的膝关节MRI半月板损伤智能诊断模型研究

目的构建一个用于诊断膝关节MRI半月板损伤的多任务学习的智能诊断模型MCSNetatt,并将模型诊断结果与临床医师在有无模型辅助条件下的诊断结果进行对比分析,评估模型在临床应用中的实际效果。方法回顾分析2021年1月至2022年12月,我院接受膝关节MRI检查及随后行关节镜手术的259例患者诊疗资料,将患者资料按照159∶50∶50进行模型训练、验证及测试。使构建的单任务学习模型CNetatt、未增加注意力机制的多任务学习模型MCSNet和增加注意力机制的多任务学习模型MCSNetatt 3个模型分别评估内、外侧半月板损伤情况,同时让2位临床医师在有无模型辅助条件下分别对内、外侧半月板损伤进行诊断。研究以关节镜检查结果为金标准,对比分析准确率、精确度、召回率、F1评分、接受者工作特征曲线下面积(area under the receiver operating characteristic curve,AUC)和接受者工作特征曲线(receiver operating characteristic curve,ROC)等评估指标。结果MCSNetatt模型诊断内、外侧半月板损伤的F1评分分别为0.930和0.900,优于CNetatt模型和MCSNet模型。MCSNetatt模型在诊断内、外侧半月板损伤时的准确率分别为0.940和0.920,精确度分别为0.947和0.909,均优于2位临床医师。在MCSNetatt模型辅助下,2位医师对内、外侧半月板损伤诊断结果均有明显提升。结论基于多任务学习的模型MCSNetatt可辅助临床医师高效且准确诊断膝关节半月板损伤。

位移幅值对砾石-格栅界面循环剪切特性的影响

由于加筋土结构经常受到动荷载的作用,因此筋土界面的动力剪切性能也越来越受到重视;但目前筋土界面的动力剪切试验往往循环次数很少,一般只有10多次,不能充分反映筋土界面的动力相互作用。采用大型动态直剪仪,在剪切位移幅值分别为1、2、4、6 mm时,对砾石-格栅界面进行了2000次水平循环直剪试验,分析了剪切位移幅值对筋土界面剪切应力、竖向位移以及颗粒破碎的影响,揭示了筋土界面相互作用的机理。结果表明:在循环剪切过程中,界面平均峰值剪切应力先增加后减小;剪切位移幅值越大,达到界面峰值强度所需的循环次数越少,而达到界面残余强度所需的循环次数越多,较大的剪切位移幅值会使得砾石-格栅界面的剪切应力衰减现象更显著;随着剪切位移幅值的增大,试样最终剪缩量增大,但试样最终剪缩量增量逐渐减小;随着剪切位移幅值增大,界面剪切刚度逐渐减小,界面阻尼比却逐渐增大;通过对循环剪切试验后的砾石颗粒各粒组含量进行分析,发现剪切位移幅值越大,颗粒的相对破碎率也越大,相对颗粒破碎率与剪切位移幅值呈较好的对数关系,并与试验结果吻合较好。