The superplasticity of Al-6Mg-0.4Mn-0.25Sc-0.12Zr and Al-6Mg-0.4Mn-0.25Er-0.12Zr(mass fraction,%)alloys sheet was investigated,and the effect of Sc and Er was discussed.The results show that the superplastic ductiliti...The superplasticity of Al-6Mg-0.4Mn-0.25Sc-0.12Zr and Al-6Mg-0.4Mn-0.25Er-0.12Zr(mass fraction,%)alloys sheet was investigated,and the effect of Sc and Er was discussed.The results show that the superplastic ductilities of Al-Mg-Mn-Sc-Zr alloy was higher than that of Al-Mg-Mn-Er-Zr alloy at a wide temperature range of 400-540°C and high strain rate range of1.67×10-4-1.67×10-1 s-1.A maximum elongation 673%is obtained at 520°C and 1.67×10-3 s-1 in the Sc-containing alloy;while the Er-containing alloy only gets a maximum elongation 253%at 520°C and 1.67×10-3 s-1.Moreover,the average stress exponent of Sc-containing alloy is about 2.84,which is smaller than that of Er-containing alloy(3.64).Besides,the activation energies of the Sc-containing and Er-containing alloy are 84.8 k J/mol and 87.2 k J/mol,respectively.It is indicated that grain boundary sliding is the dominant mechanism during tensile deformation.According to microstructure examination,the better superplasticity of Sc-containing alloy may be attributed to the presence of Al3_(Sc,Zr)dispersoids,which can inhibit recrystallization and grain growth effectively.展开更多
The detection performance is evaluated for our proposed analog multiuser receiver in Ultra-WideBand (UWB) transmitted-reference system. In the presence of dense multipath and multi-access signals,the performance analy...The detection performance is evaluated for our proposed analog multiuser receiver in Ultra-WideBand (UWB) transmitted-reference system. In the presence of dense multipath and multi-access signals,the performance analysis is difficult due to the complicated waveform of received impulse. We develop an approach to analyze the steady-state Signal-to-Interference-plus-Noise (SINR) of the detector output. The multipath-spread impulse is fitted to an exponentially decaying profile in the analysis. A closed-form expression of steady-state SINR is further deduced for the proposed Least Minimum Square (LMS) detector. The analysis is validated by simulations in Line-Of-Sight (LOS) and Non-Line-Of-Sight (NLOS) channel respectively. Based on the theoretical results,the multipath delay spread is employed to determine the optimal width of the integration window of the detector.展开更多
With the help of the zero-curvature equation and the super trace identity, we derive a super extensionof the Kaup-Newell hierarchy associated with a 3×3 matrix spectral problem and establish its super bi-Hamilton...With the help of the zero-curvature equation and the super trace identity, we derive a super extensionof the Kaup-Newell hierarchy associated with a 3×3 matrix spectral problem and establish its super bi-Hamiltonianstructures.Furthermore, infinite conservation laws of the super Kaup-Newell equation are obtained by using spectralparameter expansions.展开更多
In this thesis,construction industries face with the major challenges are cost overruns and time delays, which have existed in most of projects, especially in developing countries. Construction projects and the enviro...In this thesis,construction industries face with the major challenges are cost overruns and time delays, which have existed in most of projects, especially in developing countries. Construction projects and the environment are increasingly complex, thus it has greater demands on project managers and cost managers that deliver processes on time. However the process of construction is limited to unforeseeable and variable factors, resulting from many sources. The aim of the report is to analyze determining factors about causing budget overrun and time delays by reviewing and identifying past cases. Furthermore, the construction process is made up of three critical phases, i.e. conception, design, construction. Generally, the majority of time delays and cost overrun happen in the period of construction, where many factors are always unforeseeable, and time delays usually associate with cost overruns. （Chan and Kumaraswamy, 1997）展开更多
基金Project(2014M552149) supported by the China Postdoctoral Science FoundationProject(CX2016B041) supported by the Hunan Provincial Innovation Foundation For Postgraduate,ChinaProject(CSUZC201614) supported by the Open-End Fund for the Valuable and Precision Instruments of Central South University,China
文摘The superplasticity of Al-6Mg-0.4Mn-0.25Sc-0.12Zr and Al-6Mg-0.4Mn-0.25Er-0.12Zr(mass fraction,%)alloys sheet was investigated,and the effect of Sc and Er was discussed.The results show that the superplastic ductilities of Al-Mg-Mn-Sc-Zr alloy was higher than that of Al-Mg-Mn-Er-Zr alloy at a wide temperature range of 400-540°C and high strain rate range of1.67×10-4-1.67×10-1 s-1.A maximum elongation 673%is obtained at 520°C and 1.67×10-3 s-1 in the Sc-containing alloy;while the Er-containing alloy only gets a maximum elongation 253%at 520°C and 1.67×10-3 s-1.Moreover,the average stress exponent of Sc-containing alloy is about 2.84,which is smaller than that of Er-containing alloy(3.64).Besides,the activation energies of the Sc-containing and Er-containing alloy are 84.8 k J/mol and 87.2 k J/mol,respectively.It is indicated that grain boundary sliding is the dominant mechanism during tensile deformation.According to microstructure examination,the better superplasticity of Sc-containing alloy may be attributed to the presence of Al3_(Sc,Zr)dispersoids,which can inhibit recrystallization and grain growth effectively.
基金Supported by the Guangxi Natural Science Foundation (No.0731025, No.0731026)the Established Project by Guangxi Education Department (No.200808LX117)
文摘The detection performance is evaluated for our proposed analog multiuser receiver in Ultra-WideBand (UWB) transmitted-reference system. In the presence of dense multipath and multi-access signals,the performance analysis is difficult due to the complicated waveform of received impulse. We develop an approach to analyze the steady-state Signal-to-Interference-plus-Noise (SINR) of the detector output. The multipath-spread impulse is fitted to an exponentially decaying profile in the analysis. A closed-form expression of steady-state SINR is further deduced for the proposed Least Minimum Square (LMS) detector. The analysis is validated by simulations in Line-Of-Sight (LOS) and Non-Line-Of-Sight (NLOS) channel respectively. Based on the theoretical results,the multipath delay spread is employed to determine the optimal width of the integration window of the detector.
基金Supported by National Natural Science Foundation of China under Grant No.10871182 Innovation Scientists and Technicians Troop Construction Projects of Henan Province (084200410019)SRFDP (200804590008)
文摘With the help of the zero-curvature equation and the super trace identity, we derive a super extensionof the Kaup-Newell hierarchy associated with a 3×3 matrix spectral problem and establish its super bi-Hamiltonianstructures.Furthermore, infinite conservation laws of the super Kaup-Newell equation are obtained by using spectralparameter expansions.
文摘In this thesis,construction industries face with the major challenges are cost overruns and time delays, which have existed in most of projects, especially in developing countries. Construction projects and the environment are increasingly complex, thus it has greater demands on project managers and cost managers that deliver processes on time. However the process of construction is limited to unforeseeable and variable factors, resulting from many sources. The aim of the report is to analyze determining factors about causing budget overrun and time delays by reviewing and identifying past cases. Furthermore, the construction process is made up of three critical phases, i.e. conception, design, construction. Generally, the majority of time delays and cost overrun happen in the period of construction, where many factors are always unforeseeable, and time delays usually associate with cost overruns. （Chan and Kumaraswamy, 1997）
