黄河改道以来黄河三角洲演变过程及其驱动机制.

基于1976--2009年的23期遥感影像,并结合1976--2008年利津站水沙数据以及黄河流域年均降水量数据,定量分析黄河入海水沙特征以及黄河三角洲演变过程及其驱动机制.结果表明:1976--2008年间,黄河入海年径流量和年输沙量呈现出年际变化大和丰枯水(沙)年交替的特征,但总体均呈下降趋势;清水沟流路河口三角洲岸线和面积变化总体呈淤积增长趋势,三角洲的发育过程大致分1976--1985年,1986--1995年和1996--2009年3个阶段,3个阶段的增长速率逐阶段递减;黄河三角洲岸线和面积与利津站累积输沙量之间均呈显著的指数函数关系;黄河流域降水量的年际波动与利津站入海输沙量年际波动基本同步,并具有相关性,说明黄河流域降水量的年际波动是引起入海径流量和输沙量波动的重要原

高性能医用钴基合金强化机理的研究进展

MP35N合金是一种高性能医用钴基合金,具有优良力学性能、耐腐蚀和良好的生物相容性等优点,在医疗器械和航天航空具有广阔的应用前景。综述MP35N合金的力学性能和两种强化工艺冷变形和时效处理对其性能的影响,将MP35N合金强化机理分为4类并加以详细阐述,描述不同强化机理的发展历程和现状。分析MP35N合金不同强化机理的优缺点和未来关于MP35N合金的研究思路

山东半岛北部黑松海防林幼龄植株更新动态及其影响因素

<正>海防林是人工林生态网络系统的重要组成部分,也是海岸带地区典型的生态系统类型。印度洋海啸发生后,中国更加重视沿海防护林体系建设,制定了《全国沿海防护林体系建设工程规划(2006—2015年)》,规划土地总面积为4 471万hm2,占国土 &nbsp

一种钴基合金丝的时效处理方法

本发明公开了一种钴基合金丝的时效处理方法，包括以下步骤：(1)将装有粒径小于500um的砂子的加热炉加热至所需的时效温度；(2)将加工到所需直径的钴基合金丝插入步骤(1)的砂子中保温所需的时效时长；本发明的时效处理方法保证钴基合金丝加热温度恒定，还可以避免钴基合金丝直接接触空气，防止氧化；快速升温到时效温度以及缩短保温时间，可以有利于缺陷消除和原子偏析，同时还可以避免晶粒粗大，有利于提高钴基合金丝的强度同时保证其韧性不下降；可以避免真空加热条件下要求的严格的密封性、操作复杂性和抽放真空的长时性等问题，操作方便效率高；解决钴基合金丝组织不均匀问题，可以有利于扩大用于线圈热处理

Effects of simulated precipitation changes on plant community characteristics of wetland in the Yellow River Delta, China

Under the changing climate scenario, changes in precipitation regimes are expected to alter soil water and salinity conditions, with consequences on the characteristics of plant community in estuarine wetland. Here, we used a six-year (2015-2020) precipitation manipulation experiment to examine how plant community characteristics responded to precipitation changes in the Yellow River Delta. The results showed that soil electrical conductivity significantly decreased, while soil moisture significantly increased with increasing precipitation. Precipitation changes altered plant community composition. Increased precipitation reduced the absolute dominance of Suaeda glauca and Suaeda salsa, but increased that of Triarrhena sacchariflora and Imperata cylindrica. Shannon index and Margalef richness index of plant community significantly increased with increasing precipitation. Compared with the control, both decreased and increased precipitation decreased the plant community abundance, frequency and coverage. The treatment of 60% increased precipitation significantly decreased plant community frequency by 54.9%, while the 60% decreased precipitation, 40% decreased precipitation, 40% increased precipitation and 60% increased precipitation treatment significantly decreased plant abundance by 38.9%, 33.8%, 35.8% and 45.7%, respectively. The aboveground biomass significantly increased with increasing precipitation, but aboveground plant biomass under 60% increased precipitation treatment being lower than that reducing under 40% increased precipitation treatment, probably due to the negative effects of flooding stress. In addition, Margalef richness index had a significantly positive relationship with aboveground biomass. Aboveground biomass, Shannon diversity index, Margalef richness index, and Simpson diversity index were negatively related to soil electrical conductivity, and aboveground plant biomass was positively related to soil moisture. Our results revealed that precipitation changes regulate growth characteristics, species composition, and diversity of plant community by altering soil water and salinity conditions in a coastal wetland

一种可实现定位调姿的多自由度冗余机械臂

本发明涉及一种可实现定位调姿的多自由度冗余机械臂，包括机械臂定位调姿机构和机械臂末端调姿机构，其中机械臂末端调姿机构包括关节连接板、末端移动关节和末端调姿关节，所述关节连接板安装于所述机械臂定位调姿机构末端，所述末端移动关节包括移动驱动装置、关节架体和移动传动组件，所述关节架体与所述关节连接板滑动连接并通过所述移动驱动装置驱动移动，并且所述移动驱动装置通过所述移动传动组件传递转矩，所述关节架体下端设有末端调姿关节，且所述末端调姿关节与末端设备连接。本发明通过自由度的合理配置以及通过添加冗余自由度实现了机械臂大空间范围调姿运动，同时还可以在确定末端设备中心的条件下实现设备调整，从而实现定位调姿

豫西祁雨沟矿区189矿体流体包裹体研究及其对找矿的指示意义

祁雨沟矿区地处华北板块南缘,区内金属矿产资源丰富。区域出露地层从下到上分别是太古宇-元古宇太华群、中元古界长城系熊耳群和新生界的古近系、新近系、第四系沉积物。太华群为一套长英质片麻岩和表壳岩系夹超基性-基性变质岩系组成,主要岩性有黑云斜长片麻岩、混合片麻岩和斜长角闪岩,是区内爆破角砾岩型矿体的主要围岩。熊耳群展布于区域东部和南部,整合于太华群之上

黑松海岸防护林径级分布及其与球果和种子特性的关系

为探讨黑松种群的结实规律,调查了烟台海防林中黑松的径级结构,采集了不同大小植株上的球果,分析了球果和种子特性.结果表明:黑松种群径级结构为金字塔形,35.84%的植株具有生殖能力.随径级增加,球果大小(球果质量,球果长,球果宽)逐渐增加;总种鳞数逐渐增加,可育种鳞数,可育种鳞率和总种子数变化为凹形,在径级Sc6(胸径12.5~15.5cm)处最低;在径级Sc6(胸径12.5~15.5cm)处,球果结种率和胚珠败育率分别为最低和最高.球果大小与总种子数成显著正相关,与胚珠败育率成显著负相关.种子发芽率,发芽指数和活力指数随径级增加呈波浪形变化,在径级Sc3(胸径3.5~6.5cm)和Sc6(胸径12.5~15.5cm)处显著高于径级Sc4(胸径6.5~9.5cm)和Sc7(胸径15.5~18.5cm).对球果胚珠败育率的调节是黑松保证种子质量的重要途