The cutter head will be stuck when the shield machine pass through the area existing anchor left by foundation construction of surrounding high-rise building.Subsurface excavation method is an efficient way to remove ...The cutter head will be stuck when the shield machine pass through the area existing anchor left by foundation construction of surrounding high-rise building.Subsurface excavation method is an efficient way to remove the existed anchor.In this paper,a three-dimensional finite element model is developed to study stability of cross-channel excavation.The time-spatial effects of arch crown settlement,intrados uplift and side wall horizontal convergence are analyzed according to different excavation size,lining thickness and lining order.The results show that the excavation size is the main factor to control the deformation of the surrounding soil,especially in arch crown settlement;The influence of lining thickness on the spatial effect of surrounding soil deformation is obvious when the excavation size is large,but little on the time effect;The influence of the lining order on the deformation of the surrounding soil is obvious,in particular,the larger the excavation size,the more obvious advantages of the lining order.Finally,based on the time-spatial effects comparison of nine excavation schemes of the cross-channel,an optimum excavation scheme is adopted in the actual project.展开更多
A new cross-channel interference suppression method is proposed to decrease the cross-channel interference in beat signals based on the short time Fourier transform （STY3＂） and the inverse short time Fourier transf...A new cross-channel interference suppression method is proposed to decrease the cross-channel interference in beat signals based on the short time Fourier transform （STY3＂） and the inverse short time Fourier transform （ISTFT） when the dual-orthogonal polarimetric frequency-modulated continu- ous wave （FMCW） radar adopts the opposite-slope linear frequency modulation signal pair in the simultaneous measurement mode. The STFT is applied only on the signals in the cross-interference intervals in the four polarimetric channels to decrease the computation complexity. A mask matrix for suppressing the interference is constructed using the constant false alarm ratio （CFAR） detection on the spectrograms by the STFY. The simulative results show that the cross-channel interference is effi- ciently suppressed by the proposed method. The comparison between the proposed method and the rejection method verifies the improved performance of the proposed method.展开更多
A metallic interconnect plate with a flow channel array is one of the most important elements in a solid oxide fuel cell(SOFC). Electrochemical machining(ECM) is considered to be an adoptable technology for fabricatin...A metallic interconnect plate with a flow channel array is one of the most important elements in a solid oxide fuel cell(SOFC). Electrochemical machining(ECM) is considered to be an adoptable technology for fabricating flow channels in an interconnect plate on account of its efficiency and low cost. With respect to the traditional electrolyte flow mode in ECM cross-channel array, the electrolyte usually flows from one side to the opposite side of the rectangular processing area. However, obvious flow marks are typically formed at the bottom of channels perpendicular to the flow. According to multiphysical simulation analysis, the low electrolyte velocity in the channels perpendicular to the flow leads to uneven distribution of electrolyte products. To improve the uniformity of the flow field, two new electrolyte flow modes, “two-in and two-out” and “three-in and one-out”, are proposed. By adding one or two additional electrolyte inlets to the sides of the traditional flow field, the electrolyte flow velocity in the channels perpendicular to the traditional flow will be increased. Corresponding simulations and experiments were performed and the results showed that the “three-in and one-out” flow mode can produce a flatter bottom surface for the cross-channel array. Parameter optimization experiments for the preferred flow mode were undertaken and the optimal flow field parameters were determined.展开更多
基金The National Natural Science Foundation of China(No.41404096,51678536,51509224)The Scientific and Technological Research Program of Henan Province(No.152102310066)Outstanding Young Talent Research Fund of Zhengzhou University(1621323001)for which the authors are grateful.
文摘The cutter head will be stuck when the shield machine pass through the area existing anchor left by foundation construction of surrounding high-rise building.Subsurface excavation method is an efficient way to remove the existed anchor.In this paper,a three-dimensional finite element model is developed to study stability of cross-channel excavation.The time-spatial effects of arch crown settlement,intrados uplift and side wall horizontal convergence are analyzed according to different excavation size,lining thickness and lining order.The results show that the excavation size is the main factor to control the deformation of the surrounding soil,especially in arch crown settlement;The influence of lining thickness on the spatial effect of surrounding soil deformation is obvious when the excavation size is large,but little on the time effect;The influence of the lining order on the deformation of the surrounding soil is obvious,in particular,the larger the excavation size,the more obvious advantages of the lining order.Finally,based on the time-spatial effects comparison of nine excavation schemes of the cross-channel,an optimum excavation scheme is adopted in the actual project.
基金Supported by the National Natural Science Foundation of China for Youth(No.41301397)
文摘A new cross-channel interference suppression method is proposed to decrease the cross-channel interference in beat signals based on the short time Fourier transform （STY3＂） and the inverse short time Fourier transform （ISTFT） when the dual-orthogonal polarimetric frequency-modulated continu- ous wave （FMCW） radar adopts the opposite-slope linear frequency modulation signal pair in the simultaneous measurement mode. The STFT is applied only on the signals in the cross-interference intervals in the four polarimetric channels to decrease the computation complexity. A mask matrix for suppressing the interference is constructed using the constant false alarm ratio （CFAR） detection on the spectrograms by the STFY. The simulative results show that the cross-channel interference is effi- ciently suppressed by the proposed method. The comparison between the proposed method and the rejection method verifies the improved performance of the proposed method.
基金co-supported by the Joint Funds of the Natural Science Foundation of China and Guangdong Province(No.U1601201)the Natural Science Foundation of Jiangsu Province(No.BK20192007)the National Natural Science Foundation of China for Creative Research Groups(No.51921003)。
文摘A metallic interconnect plate with a flow channel array is one of the most important elements in a solid oxide fuel cell(SOFC). Electrochemical machining(ECM) is considered to be an adoptable technology for fabricating flow channels in an interconnect plate on account of its efficiency and low cost. With respect to the traditional electrolyte flow mode in ECM cross-channel array, the electrolyte usually flows from one side to the opposite side of the rectangular processing area. However, obvious flow marks are typically formed at the bottom of channels perpendicular to the flow. According to multiphysical simulation analysis, the low electrolyte velocity in the channels perpendicular to the flow leads to uneven distribution of electrolyte products. To improve the uniformity of the flow field, two new electrolyte flow modes, “two-in and two-out” and “three-in and one-out”, are proposed. By adding one or two additional electrolyte inlets to the sides of the traditional flow field, the electrolyte flow velocity in the channels perpendicular to the traditional flow will be increased. Corresponding simulations and experiments were performed and the results showed that the “three-in and one-out” flow mode can produce a flatter bottom surface for the cross-channel array. Parameter optimization experiments for the preferred flow mode were undertaken and the optimal flow field parameters were determined.
文摘物联网设备的爆发式增长推进了异构无线设备互联互通的进程,跨网通信技术(Cross-Technology Communication,CTC)允许同一频段下遵循不同底层协议的无线设备在无需网关的前提下实现直联,但移动状态下的双向跨网通信方法仍缺乏系统的研究.本文提出了一种基于能量感知的跨网通信方案——MobiCTC,它支持WiFi与Zig‑Bee设备移动状态下的双向跨网通信.WiFi到ZigBee方向,该方案利用RSSI(Received Signal Strength Indicator)作为解码信息,基于能级映射实现信息解码;ZigBee到WiFi方向,该方案采用CSI(Channel State Information)作为解码信息,充分挖掘CSI的幅度与相位信息,利用机器学习方法实现分类解码.最后,本文使用TelosB节点和USRP X310平台对MobiCTC方案进行了实验验证.实验结果表明,移动状态下WiFi到ZigBee方向的系统吞吐量为139.535 bps,较WiZig提高了1.82倍,符号错误率为0.016,与WiZig基本持平;ZigBee到WiFi方向的系统吞吐量为250 bps,较FreeBee提高了15.7%,符号错误率为0.0516,较ZigFi下降了23.21%.
