End-member characteristics of sediment grain size of modern Yellow River Delta sediments and their response to channel shifts and human activities

Yellow River Delta sediments record environmental changes in the Yellow River basin at long time scales, and respond sensitively to natural and human activities such as river diversions and reservoir construction in the basin. We analyzed the grain size distribution of core YDC from onshore delta since 1976 near the river mouth were analyzed using a parametric end-member analysis model. Results show that EM1 and EM2 are composed of fine-grained clay and fine powder sand, deposited under weak hydrodynamic conditions for long distance transport in the Yellow River, while EM3 and EM4 are coarse powder sand fractions, deposited by wave and tidal action under stronger dynamic conditions. By comparing the data on channel alteration and human activities, and combining data from previous studies on sedimentation rates in the Yellow River estuary, we found that significant changes in grain size characteristics could be used as reference points for sediment age determination. The grain size parameters and end element data reflect the natural and human activities since 1976, such as the diversion of the Yellow River from Qingshuigou to the sea, the construction of the Longyangxia Reservoir, and the diversion of the Yellow River from Qingbacha to the sea. This study provide a reference for the management of the Yellow River Delta estuary and coastal engineering construction, and a scientific basis for ecological protection and high-quality development of the Yellow River basin

两种实现方式的改进型光双二进制性能分析

文章仿真研究了两种改进型光双二进制调制格式。首先对比分析了产生两种改进型光双二进制调制格式的发射机结构及两种调制格式的码型和频谱特性,随后进行了系统的传输性能仿真。仿真结果表明:当残留色散较大时,改进Ⅱ型光双二进制调制格式性能较为优异;而在-13.22.8dBm入纤光功率范围内,与改进Ⅱ型光双二进制和NRZ（非归零）码调制格式相比,改进Ⅰ型光双二进制的Q值最高,抗非线性效应能力最强

石墨表面镀Si对石墨/Al复合材料热物理性能的影响

研究了石墨粒径及表面镀Si处理对石墨/Al复合材料热物理性能的影响。结果表明:在盐浴过程中石墨表面形成了SiC层,这不仅增强了石墨-Si/Al复合材料的界面结合力,而且抑制了Al4C3相的产生。随着石墨鳞片体积分数从50%增加到70%,复合材料X-Y方向的热导率从492 W/(m·K)增加到654 W/(m·K),而且体积分数为50%的镀Si石墨/Al复合材料抗弯强度达到了81 MPa,相比未镀覆的提高了53%,是理想的定向导热电子封装材料。随着石墨粒径从500μm减小到150μm,石墨-Si/Al复合材料X-Y面方向的热导率由654 W/(m·K)降低到445 W/(m·K),但Z方向的热导率和复合材料抗弯强度变化不明显