A new direction synthetic method for monostatic multiple input multiple output (MIMO) radar is presented based on synthetic impulse and aperture radar (SIAR) system. Concerned with the monostatic MIMO radar which simu...A new direction synthetic method for monostatic multiple input multiple output (MIMO) radar is presented based on synthetic impulse and aperture radar (SIAR) system. Concerned with the monostatic MIMO radar which simultaneously emits orthogonal signals with multi-carrier-frequency and possesses sparsely distributed transmitting and receiving arrays with respective location, as well as the situation for the presence of multipath propagation in the low flying target’s echo, the method integrates the aperture of the transmitting arrays with the receiving arrays to form the digital beam-forming (DBF) in azimuth and elevation dimensions. And a study has been made of planar general MUSIC algorithm based on decorrelating the multipath signals of multi-carrier-frequency MIMO radar. Through compensat-ing the phase delay of both the transmitting and the receiving arrays and synthe-sizing the transmitting beam in two dimensions at the receiver, the angular resolu-tion and measurement accuracy are improved and the computational complexity is reduced after transforming the three-dimensional (3D) parameter estimation prob-lem into a two-dimensional (2D) one. Finally, the Cramer-Rao Bounds (CRBs) of DOA estimation for azimuth and elevation is put forward with the exsiting multipath propagation. Results of computer simulation demonstrate the validity of the new method.展开更多
为研究岩溶与非岩溶小流域水循环和氮循环的差异,该研究选取漓江流域青狮潭水库灌区内以农业为主的睦洞岩溶小流域和金龟非岩溶小流域为研究对象,利用水的氢氧同位素和硝酸盐的氮氧同位素结合贝叶斯同位素混合模型(Bayesian Model Stabl...为研究岩溶与非岩溶小流域水循环和氮循环的差异,该研究选取漓江流域青狮潭水库灌区内以农业为主的睦洞岩溶小流域和金龟非岩溶小流域为研究对象,利用水的氢氧同位素和硝酸盐的氮氧同位素结合贝叶斯同位素混合模型(Bayesian Model Stable Isotope Analysis in R,SIAR),对比两个小流域水体硝酸盐的污染源以及迁移过程。结果表明:水体硝酸盐污染的时空分布受流域水文地质及其伴生的地形地貌、土壤特性和土地利用类型的影响,以耕地为主且土壤层分布不连续的睦洞小流域水体硝酸盐的浓度均值(0.19~15.84 mg/L)、水的氢氧同位素(分别为-44.08‰~-19.63‰和-7.24‰~-1.55‰)以及硝酸盐的氮氧同位素(-1.65‰~53.98‰和0.04‰~13.74‰)值域都宽于以林地为主且土壤层相对较深厚的金龟非岩溶小流域;空间分布上,睦洞小流域北部补给区裸露岩溶石山果园下渗的氮肥和中部密集村庄下渗的动物粪便/生活污水在中部构造盆地区分散排泄不畅,造成G4~G7采样点井水的NO_(3)^(¯)浓度均值(11.96~15.84 mg/L)以及氮氧同位素丰度值(分别为0.65‰~28.23‰和2.46‰~14.43‰)偏高;时间尺度上,睦洞小流域碳酸盐岩风化形成的浅薄土壤层持水能力差且渗透性强,导致旱季土壤N和雨季动物粪便/生活污水对水体NO_(3)^(¯)的贡献率小于同季节的金龟小流域。研究结果可为岩溶与非岩溶区水环境治理提供科学依据。展开更多
掌握沉积物-水界面氮的循环过程,对有效控制地表水氮污染具有关键的作用.通过采集西湖不同季节的柱状芯样,利用氮、氧同位素技术及稳定同位素源解析模型(stable isotope analysis in R,SIAR)并结合乙炔抑制法研究沉积物-水界面氮的来源...掌握沉积物-水界面氮的循环过程,对有效控制地表水氮污染具有关键的作用.通过采集西湖不同季节的柱状芯样,利用氮、氧同位素技术及稳定同位素源解析模型(stable isotope analysis in R,SIAR)并结合乙炔抑制法研究沉积物-水界面氮的来源及迁移转化.结果表明,硝酸盐(NO_3^-)和氨氮(NH_4^+)在沉积物-水界面均存在浓度梯度,NO_3^-自底层水向间隙水扩散,是为沉积物累积;NH_4^+自间隙水向底层水扩散,是为沉积物释放.西湖底层水硝化作用明显,硝酸盐来源包括生活污水(粪肥)、土壤氮、化肥和降雨,生活污水(粪肥)是主要来源,其在夏季贡献率高达60.8%.间隙水中特别高的δ15N值反映西湖沉积物-水界面存在强烈的反硝化作用.西湖沉积物-水界面硝化速率和反硝化速率的平均值分别为2.85 mmol·(m^2·d)^(-1)和23.51μmol·(m^2·d)^(-1),沉积物-水界面在水体氮素去除过程中作用显著.硝化速率和反硝化速率时空变化显著.温度和溶解氧是影响西湖沉积物-水界面氮迁移转化的主要因素.展开更多
基金Supported by Program for New Century Excellent Talents in University (Grant No. NCET-06-0856) the National Natural Science Foundation of China (Grant No. 60772068)
文摘A new direction synthetic method for monostatic multiple input multiple output (MIMO) radar is presented based on synthetic impulse and aperture radar (SIAR) system. Concerned with the monostatic MIMO radar which simultaneously emits orthogonal signals with multi-carrier-frequency and possesses sparsely distributed transmitting and receiving arrays with respective location, as well as the situation for the presence of multipath propagation in the low flying target’s echo, the method integrates the aperture of the transmitting arrays with the receiving arrays to form the digital beam-forming (DBF) in azimuth and elevation dimensions. And a study has been made of planar general MUSIC algorithm based on decorrelating the multipath signals of multi-carrier-frequency MIMO radar. Through compensat-ing the phase delay of both the transmitting and the receiving arrays and synthe-sizing the transmitting beam in two dimensions at the receiver, the angular resolu-tion and measurement accuracy are improved and the computational complexity is reduced after transforming the three-dimensional (3D) parameter estimation prob-lem into a two-dimensional (2D) one. Finally, the Cramer-Rao Bounds (CRBs) of DOA estimation for azimuth and elevation is put forward with the exsiting multipath propagation. Results of computer simulation demonstrate the validity of the new method.
文摘为研究岩溶与非岩溶小流域水循环和氮循环的差异,该研究选取漓江流域青狮潭水库灌区内以农业为主的睦洞岩溶小流域和金龟非岩溶小流域为研究对象,利用水的氢氧同位素和硝酸盐的氮氧同位素结合贝叶斯同位素混合模型(Bayesian Model Stable Isotope Analysis in R,SIAR),对比两个小流域水体硝酸盐的污染源以及迁移过程。结果表明:水体硝酸盐污染的时空分布受流域水文地质及其伴生的地形地貌、土壤特性和土地利用类型的影响,以耕地为主且土壤层分布不连续的睦洞小流域水体硝酸盐的浓度均值(0.19~15.84 mg/L)、水的氢氧同位素(分别为-44.08‰~-19.63‰和-7.24‰~-1.55‰)以及硝酸盐的氮氧同位素(-1.65‰~53.98‰和0.04‰~13.74‰)值域都宽于以林地为主且土壤层相对较深厚的金龟非岩溶小流域;空间分布上,睦洞小流域北部补给区裸露岩溶石山果园下渗的氮肥和中部密集村庄下渗的动物粪便/生活污水在中部构造盆地区分散排泄不畅,造成G4~G7采样点井水的NO_(3)^(¯)浓度均值(11.96~15.84 mg/L)以及氮氧同位素丰度值(分别为0.65‰~28.23‰和2.46‰~14.43‰)偏高;时间尺度上,睦洞小流域碳酸盐岩风化形成的浅薄土壤层持水能力差且渗透性强,导致旱季土壤N和雨季动物粪便/生活污水对水体NO_(3)^(¯)的贡献率小于同季节的金龟小流域。研究结果可为岩溶与非岩溶区水环境治理提供科学依据。
