湿地中的藻类生态学研究进展

从湿地中藻类的种群结构、藻类在湿地中的功能、湿地中的藻类生产力及其影响因素等方面综述了天然湿地中的藻类生态学研究进展 .湿地植物区系主要有附泥藻类、附植藻类、后周丛藻类和浮游植物4种类型 ,其中常见的是附泥藻类的硅藻、绿藻和蓝藻 .藻类最显著的作用是作为湿地食物网中的初级生产者 ,也作为湿地环境污染的生物指示物 .影响藻类生产力的因素有水力学因素、营养、温度、光、大型植物及草食动物和其它动物 .未来对藻类的研究应侧重于湿地藻类生物多样性、藻类生物量、生产力、种群组成的环境控制及其相互关系 ,以及藻类作为

四川永兴汉墓出土染色绢分析

通过对四川绵阳市东郊永兴汉墓出土染色绢的现代检测分析,对其纤维属性、织物组织、染料品种进行了判定,指出其在研究四川蚕桑丝绸史及中国古代染色史上具有重要意义

一种激光表面改性的图像评价方法

本发明提供了一种激光表面改性的图像评价方法，包括如下步骤：将待评价的零件置于数控移动平台上；以零件最外边沿为侧边，设置一个矩形取景区，根据取景镜头的焦距和矩形取景区的尺寸，将矩形取景区划分成多个采集区域；控制取景镜头自动获取每个采集区域的子图像，并拼接成完整的矩形取景区图像，对获取的矩形取景区图像进行裁剪，以得到零件图像；确定零件图像的灰度值范围，根据零件改性后其表面不同状态在零件图像中所对应的灰度信息，计算出每个子范围所占的面积，以不同子范围对应的面积与零件的改性总面积进行比较，根据比较结果，即可得到零件改性后其表面的改性效果

脉冲激光热疲劳实验时温度的闭环控制方法

本发明提供了脉冲激光热疲劳实验时温度的闭环控制方法，先预设一个试样实验时的目标温度值，再获取试样表面在一定时间段内的温度值；计算出该时间段内的实时平均温度值、最高温度和最低温度、实时温度震荡值；然后利用预设的目标温度平均值和目标温度震荡值分别与实时温度平均值和实时温度震荡值进行偏差计算，将偏差结果代入BP神经网络PID控制模块，经过计算后得到实时工作参数；最后根据实时工作参数去调整下一时间段脉冲激光的工作状态；重复前述步骤，直至当前试样表面的实际温度值符合目标温度值的要求。本发明实现了热疲劳实验过程中脉冲激光作用区域温度的准确动态控制。为脉冲激光热疲劳实验提供了很大的便捷，大大提高了实验的可操作性与准确性

纯镍与304不锈钢激光异种焊接的工艺及其接头的组织性能

采用高密度Nd：YAG固态连续激光器对N6纯镍和304奥氏体不锈钢进行了焊接工艺实验,探究了激光功率和离焦量对焊缝成形的影响。对接头进行了拉伸强度和硬度的测试,并结合光学显微镜（OM）、扫描电镜（SEM）、能谱分析仪（EDS）等手段分析了接头的微观组织。结果表明：N6纯镍一侧热影响区晶粒长大明显,焊缝区靠近两侧熔合线附近为向焊缝中心区域生长的柱状晶,焊缝中心区域存在细小的胞晶区域;N6热影响区的显微硬度最低,焊缝的显微硬度介于N6镍母材和304不锈钢母材之间;接头拉伸断裂位置在焊缝区,抗拉强度达到N6纯镍母材的90%以上,可以满足实际情况下的使用要求。拉伸断口表现为准解理断裂

Application of millisecond pulsed laser for thermal fatigue property evaluation

An approach based on millisecond pulsed laser is proposed for thermal fatigue property evaluation in this paper. Cyclic thermal stresses and strains within millisecond interval are induced by complex and transient temperature gradients with pulsed laser heating. The influence of laser parameters on surface temperature is studied. The combination of low pulse repetition rate and high pulse energy produces small temperature oscillation, while high pulse repetition rate and low pulse energy introduces large temperature shock. The possibility of application is confirmed by two thermal fatigue tests of compacted graphite iron with different laser controlled modes. The developed approach is able to fulfill the preset temperature cycles and simulate thermal fatigue failure of engine components. (C) 2017 Elsevier Ltd. All rights reserved

Gasification Performance of Biomass in a Coupled Drafting Fixed Bed Gasifier

This paper evaluated the gasification performance of a 1.5 t/h coupled drafting fixed bed gasifier using eucalypt, and compared the operating parameters to other fixed bed gasifiers from literatures including updraft, downdraft and two-stage. The air wit

The effect of laser surface melting on grain refinement of phase separated Cu-Cr alloy

Grain refinement and homogenization of Cr phase were achieved by laser surface melting (LSM) method, and the properties of Cu-Cr alloy were significantly improved. In this study, LSM of Cu-50Cr alloy (wt.%) was conducted with a high power density (10(6) -10(7) W/cm(2)) laser beam, the microstructure and the properties of melt layer were investigated. The size of Cr phase was effectively refined from hundreds of micron scale to several micron scale, and the average size of Cr particles decreased to a few hundred nanometers. High cooling rate effectively inhibited coarsening effect on the Cr particles during liquid phase separation. Spherical Cr particles were dispersed in the melt layer with a thickness of 165 +/- 20 mu m. Microhardness was obviously enhanced and the maximum hardness was 232HV, which was 2.8 times that of the substrate. Arc duration of the LSM treated contacts increased up to 18%. The withstanding voltage of the fixed and the moving contact increased to 28.7% and 35.4%, respectively. The results show that LSM is an effective method to refine the microstructure of Cu-Cr alloy, and it is a promising modification method for electrical Cu-Cr vacuum contacts.</p

罗布泊红柳沙包落叶阳离子含量及环境指示意义/Positive ion content in organic materials of Tamarix cones and its indication to environmental change in Lop Nur Region[J]

红柳沙包沉积纹层是恢复古环境序列的一种新方法.通过对罗布泊地区红柳沙包沉积纹层中红柳落叶阳离子含量以及与环境变化关系研究表明:K+、Na+、Ca2+、Mg2+等4种阳离子平均含量分别为3.70 mg/g、40.33 mg/g、13.67 mg/g和8.08 mg/g,变化幅度排序为Ca2+＞K+＞Mg2+＞Na+.4种阳离子含量年际变化都较为明显,且变化规律较为一致,4种阳离子含量变化间的相关系数为0.653 0～0.813 8,表现为良好的正相关关系；各种阳离子与4种阳离子总量变化的相关系数为0.8144～0.9599,其中Na+含量与4种阳离子总量变化的相关系数最高,表明可以用Na+含量的变化或阳离子总量的变化分析变化趋势.阳离子含量与气温变化呈良好的正相关、与年降水量和湖水面积变化呈负相关；地下水水位降低、水质变差时,土壤水质也变差,阳离子含量增加；反之,地下水水位升高、水质变好时,土壤水质变好,阳离子含量降低.红柳落叶有机质阳离子含量的变化进一步验证了利用红柳沙包沉积纹层计年的可靠性和对罗布泊环境变化的可行性