Aiming at the potential presence of mixing automatic identification system(AIS) signals,a new demodulation scheme was proposed for separating other interfering signals in satellite systems.The combined iterative cross...Aiming at the potential presence of mixing automatic identification system(AIS) signals,a new demodulation scheme was proposed for separating other interfering signals in satellite systems.The combined iterative cross-correlation demodulation scheme,referred to as CICCD,yielded a set of single short signals based on the prior information of AIS,after the frequency,code rate and modulation index were estimated.It demodulates the corresponding short codes according to the maximum peak of cross-correlation,which is simple and easy to implement.Numerical simulations show that the bit error rate of proposed algorithm improves by about 40% compared with existing ones,and about 3 dB beyond the standard AIS receiver.In addition,the proposed demodulation scheme shows the satisfying performance and engineering value in mixing AIS environment and can also perform well in low signal-to-noise conditions.展开更多
An analytical model for the propagation of combined stress waves in a functionally graded thin-walled tube subjected to combined longitudinal and torsional impact loading is established.The material properties of the ...An analytical model for the propagation of combined stress waves in a functionally graded thin-walled tube subjected to combined longitudinal and torsional impact loading is established.The material properties of the tube are assumed to be continuously graded along the length according to a power law function with respect to the volume fractions of the constituents.The generalized characteristic theory is used to analyze the main features of the characteristic wave speeds and simple wave solutions in the functionally graded thin-walled tube.The finite difference method is used to discretize the governing equations.Two types of typical solutions are obtained for the functionally graded tube and the homogeneous tube subjected to combined longitudinal and torsional step loading.The numerical results reveal some abnormal phenomena in the stress path and wave process of the functionally graded thin-walled tube.展开更多
Mine rescue capsule is a typical emergency equipment in a coal mine.It provides a safe and confined space for miners when mining disasters occurred.The length of the passenger survival cell is suitable to be adjusted ...Mine rescue capsule is a typical emergency equipment in a coal mine.It provides a safe and confined space for miners when mining disasters occurred.The length of the passenger survival cell is suitable to be adjusted with several predefined modular cells according to various numbers of passengers.Aiming at the shortage of guidance rules for the modular combination design of mine rescue capsule,the configuration situations of survival cells are experimented with static and impact load analysis in ANSYS Workbench.The length range of a single cell,the combination schemes of miner survival section,and the effectiveness proof of assembled rescue capsules were solved sequentially by simulated load analysis on constructed structural models.The modular combination rules of the survival section are developed for variant passenger number ranging from 8 to 20.It also provides a reference for the optimal selection of rescue capsules with the same capacity.The proposed modular rules are effective for the rapid configuration design for mine rescue capsule driven by the number of passengers.展开更多
为合理地解决环境敏感区铁路线路方案综合优选问题,研究顾及环境敏感特征的铁路线路方案优选方法 .首先,基于文献调研和环境敏感区特征探析,分析总结影响线路方案的因素,构建涵盖4大方面18项指标的顾及环境敏感特征的铁路线路方案优选...为合理地解决环境敏感区铁路线路方案综合优选问题,研究顾及环境敏感特征的铁路线路方案优选方法 .首先,基于文献调研和环境敏感区特征探析,分析总结影响线路方案的因素,构建涵盖4大方面18项指标的顾及环境敏感特征的铁路线路方案优选指标体系.其次,在专家经验主观赋权和工程信息客观赋权的基础上,运用灰色关联分析理论进行组合赋权.然后,结合改进优劣解距离法(Technique for Order Preference by Similarity to an Ideal Solution, TOPSIS)确定各线路方案的相对贴近度,进而实现线路方案优选.最后,以新建铁路西宁至成都线合作至郎木寺段线路方案选择为例进行优选方法验证.研究结果表明:该区段线路的4个备选方案的相对贴近度依次为0.527 9,0.523 6,0.508 7,0.522 7,方案一的相对贴近度最大为最优方案,基于本方法的优选结果与实际专家论证结果一致;与传统TOPSIS比较,基于改进TOPSIS的运算结果避免了计算结果受单方面优势指标影响的弊端,在运算过程中将线路方案涉及的极端优劣指标进行综合权衡考量,得到的运算结果更贴近实际情况.研究成果可为未来环境敏感区线路方案优选问题提供一种新的优选思路.展开更多
Based on the 1983~2011 CMAP data,the precipitation anomaly in East Asia and its nearby sea regions（hereafter called East Asia for short） demonstrates the ＂＋-＋＂ pattern before 1999 and the ＂-＋-＂ pattern afterw...Based on the 1983~2011 CMAP data,the precipitation anomaly in East Asia and its nearby sea regions（hereafter called East Asia for short） demonstrates the ＂＋-＋＂ pattern before 1999 and the ＂-＋-＂ pattern afterwards; this decadal change is contained principally in the corresponding EOF3 component.However,the NCC_CGCM forecast results are quite different,which reveal the ＂＋-＋-＂ pattern before 1999 and the ＂-＋-＋＂ pattern afterwards.Meanwhile,the probability of improving NCC_CGCM＇s forecast accuracy based on these key SST areas is discussed,and the dynamic-statistics combined forecast scheme is constructed for increasing the information of decadal change contained in the summer precipitation in East Asia.The independent sample forecast results indicate that this forecasting scheme can effectively modify the NCC_CGCM＇s decadal change information contained in the summer precipitation in East Asia（especially in the area of 30°N–55°N）.The ACC is 0.25 and ACR is 61% for the forecasting result based on the V SST area,and the mean ACC is 0.03 and ACR is 51% for the seven key areas,which are better than NCC_CGCM＇s system error correction results（ACC is -0.01 and ACR is 49%）.Besides,the modified forecast results also provide the information that the precipitation anomaly in East Asia mainly shows the ＂＋-＋＂ pattern before 1999 and the ＂-＋-＂ pattern afterwards.展开更多
基金Project(9140C860304) supported by the National Defense Key Laboratory Foundation of China
文摘Aiming at the potential presence of mixing automatic identification system(AIS) signals,a new demodulation scheme was proposed for separating other interfering signals in satellite systems.The combined iterative cross-correlation demodulation scheme,referred to as CICCD,yielded a set of single short signals based on the prior information of AIS,after the frequency,code rate and modulation index were estimated.It demodulates the corresponding short codes according to the maximum peak of cross-correlation,which is simple and easy to implement.Numerical simulations show that the bit error rate of proposed algorithm improves by about 40% compared with existing ones,and about 3 dB beyond the standard AIS receiver.In addition,the proposed demodulation scheme shows the satisfying performance and engineering value in mixing AIS environment and can also perform well in low signal-to-noise conditions.
文摘An analytical model for the propagation of combined stress waves in a functionally graded thin-walled tube subjected to combined longitudinal and torsional impact loading is established.The material properties of the tube are assumed to be continuously graded along the length according to a power law function with respect to the volume fractions of the constituents.The generalized characteristic theory is used to analyze the main features of the characteristic wave speeds and simple wave solutions in the functionally graded thin-walled tube.The finite difference method is used to discretize the governing equations.Two types of typical solutions are obtained for the functionally graded tube and the homogeneous tube subjected to combined longitudinal and torsional step loading.The numerical results reveal some abnormal phenomena in the stress path and wave process of the functionally graded thin-walled tube.
基金National Natural Science Foundation of China(No.51475459)Fundamental Research Funds for the Central Universities of China(No.2017XKQY040)Priority Academic Program Development of Jiangsu Higher Education Institutions of China(No.PAPD)
文摘Mine rescue capsule is a typical emergency equipment in a coal mine.It provides a safe and confined space for miners when mining disasters occurred.The length of the passenger survival cell is suitable to be adjusted with several predefined modular cells according to various numbers of passengers.Aiming at the shortage of guidance rules for the modular combination design of mine rescue capsule,the configuration situations of survival cells are experimented with static and impact load analysis in ANSYS Workbench.The length range of a single cell,the combination schemes of miner survival section,and the effectiveness proof of assembled rescue capsules were solved sequentially by simulated load analysis on constructed structural models.The modular combination rules of the survival section are developed for variant passenger number ranging from 8 to 20.It also provides a reference for the optimal selection of rescue capsules with the same capacity.The proposed modular rules are effective for the rapid configuration design for mine rescue capsule driven by the number of passengers.
文摘为合理地解决环境敏感区铁路线路方案综合优选问题,研究顾及环境敏感特征的铁路线路方案优选方法 .首先,基于文献调研和环境敏感区特征探析,分析总结影响线路方案的因素,构建涵盖4大方面18项指标的顾及环境敏感特征的铁路线路方案优选指标体系.其次,在专家经验主观赋权和工程信息客观赋权的基础上,运用灰色关联分析理论进行组合赋权.然后,结合改进优劣解距离法(Technique for Order Preference by Similarity to an Ideal Solution, TOPSIS)确定各线路方案的相对贴近度,进而实现线路方案优选.最后,以新建铁路西宁至成都线合作至郎木寺段线路方案选择为例进行优选方法验证.研究结果表明:该区段线路的4个备选方案的相对贴近度依次为0.527 9,0.523 6,0.508 7,0.522 7,方案一的相对贴近度最大为最优方案,基于本方法的优选结果与实际专家论证结果一致;与传统TOPSIS比较,基于改进TOPSIS的运算结果避免了计算结果受单方面优势指标影响的弊端,在运算过程中将线路方案涉及的极端优劣指标进行综合权衡考量,得到的运算结果更贴近实际情况.研究成果可为未来环境敏感区线路方案优选问题提供一种新的优选思路.
基金supported by the National Basic Research Program of China(Grant No.2012CB955203)the National Natural Science Foundation of China(Grant Nos.41205040,41105055)the Special Scientific Research Project for Public Interest(Grant No.GYHY201306021)
文摘Based on the 1983~2011 CMAP data,the precipitation anomaly in East Asia and its nearby sea regions（hereafter called East Asia for short） demonstrates the ＂＋-＋＂ pattern before 1999 and the ＂-＋-＂ pattern afterwards; this decadal change is contained principally in the corresponding EOF3 component.However,the NCC_CGCM forecast results are quite different,which reveal the ＂＋-＋-＂ pattern before 1999 and the ＂-＋-＋＂ pattern afterwards.Meanwhile,the probability of improving NCC_CGCM＇s forecast accuracy based on these key SST areas is discussed,and the dynamic-statistics combined forecast scheme is constructed for increasing the information of decadal change contained in the summer precipitation in East Asia.The independent sample forecast results indicate that this forecasting scheme can effectively modify the NCC_CGCM＇s decadal change information contained in the summer precipitation in East Asia（especially in the area of 30°N–55°N）.The ACC is 0.25 and ACR is 61% for the forecasting result based on the V SST area,and the mean ACC is 0.03 and ACR is 51% for the seven key areas,which are better than NCC_CGCM＇s system error correction results（ACC is -0.01 and ACR is 49%）.Besides,the modified forecast results also provide the information that the precipitation anomaly in East Asia mainly shows the ＂＋-＋＂ pattern before 1999 and the ＂-＋-＂ pattern afterwards.
