波浪循环荷载作用下盾构穿越海堤过程中下卧软土的弱化响应研究#br#

 During the sub-sea tunnelling through a seawall, the soil adjacent to the tunnel may simultaneously bear tunneling-induced stress relief and wave-induced cyclic shearing. To investigate the coupling effects of stress relief and repeated loading on the mechanical behaviors of soft clay, a series of experiments were carried out using a hollow cylinder apparatus, which imposed undrained cyclic shearing to the soil samples under a reducing confining stress, followed by undrained shearing. The cyclic stresses simulated in the tests were estimated using elastic solution for a seabed subjected to the wave loadings. The test results show that the variation of each stress component under the coupled loading follows a sine or cosine relationship. The coupled loading plays a more significant role in affecting the radial strain (εr) and hoop strain (εθ) than the vertical strain (εr) and the torsional shear strain (εzθ) of the soft clay. The shear modulus of the soil experiences more degradation under the coupled loading than that under the single action of cyclic shearing. The pore pressure of the soil reduces under the disturbance of shield construction and begins to increase slowly under the wave loading after construction. At a given cyclic magnitude, the reduction of soil strength significantly depends on the magnitude of stress relief. A larger stress relief leads to a more reduction in the post-cyclic shear strength of the soil. Based on the experimental findings presented above, it is suggested that coupling effect between the cyclic shearing and the stress relief should be taken into account while designing sub-sea tunneling through a seawall.     

当前企业网络安全管理应用初探

随着经济的快速发展,我国企业规模和数量不断增加,而21世纪是科学技术快速发展的世纪,随着我国信息技术的快速发展,企业网络的安全管理问题成为了企业密切关注的热点话题。接下来我就根据我自身从事多年信息工作的经验,来具体的对企业网络安全管理的问题进行详细的探讨和分析,并根据当前的安全网络问题提出相应的防范措施。     

一种应用于2.2GHz的射频功率放大器设计

采用Cree公司提供的CGH40010F GaN高电子迁移率晶体管(HEM T)作为有源器件,设计了一款工作在2.2 G Hz的射频功率放大器.利用ADS软件对功率管的偏置电路进行设计的仿真,利用阶跃式匹配方法扩展了带宽,通过对功率管寄生参数的仿真,有效地提高了功率附加效率(PA E).仿真结果表明,在2.1 GHz～2.3 GHz的频率范围内,小信号S21增益为12.03 dB～12.77 dB,大信号输出功率为40.17 dBm,功率附加效率达到61.3％.达到设计指标的要求.     

大型预制沉箱外海拖航稳性与耐波性分析

大型预制沉箱在复杂海况条件下的拖航安全是其在外海运输过程中需要关注的重点问题。该文利用AQWA构建了拖轮-缆绳-沉箱系统拖带动力学数值模型，并对风浪流作用下，大型沉箱的稳性和耐波性进行了模拟分析。结果表明：沉箱压载后可很好地满足浮游稳定性和大倾角稳性要求；沉箱运动响应受波向影响显著，顺浪与迎浪下纵摇运动剧烈，横向浪下，横摇与垂荡运动剧烈；缆力均值主要取决于流的作用，几乎与波浪无关；随着波高与波周期的增加，沉箱运动幅值和缆力最大值总体上也随之增大。综合考虑运动稳定和目前国内市场上拖轮的性能，建议大型沉箱外海拖航海况限制为四级，浪向角取135°，该值与施工单位的拖航经验值较为接近。该研究结果可为大型沉箱外海拖航方案的确定和作业窗口期的选择提供参考。     

大型煤炭企业网络信息安全体系建设实践

根据自身建设实践,对多层级大型煤炭企业网络信息安全体系建设进行了分析总结,构建覆盖互联网公有云平台、集团公司网络、二级公司网络、生产厂矿网络四个纵向层级,以及企业办公、生产制造两个横向业务场景的防护体系,在行业内具有一定的推广意义。