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负染色电镜标本制备技术是一项快速简便、效果良好、应用普遍的技术。然而,负染色操作虽然简便快速,但却不轻易就会取得满意结果。其中最重要的成功条件之一,就是要解决标本中物颗粒的均匀散布问题。为此,我们设计、制作和使用了载样环。载样环的制作如下: 1.取长约100mm、直径1μ的铜漆包线一段。 2.将该线段两端环到一起,用胶布裹在竹签的一端,形成了以竹签为柄的漆包线套。 3.一手拿一根直径3mm的玻璃棒,一手拿着漆包线套,套住该玻璃棒,以棒为模子,单方向转动竹签就形成 相似文献
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A diode laser spectrometer at 634nm and absolute frequency measurements using optical frequency comb 下载免费PDF全文
This paper reports that two identical external-cavity-diode-laser
(ECDL) based spectrometers are constructed at 634 nm referencing on
the hyperfine B-X transition R(80)8-4 of 127I2. The lasers
are stabilized on the Doppler-free absorption signals using the
third-harmonic detection technique. The instability of the
stabilized laser is measured to be 2.8×10-12 (after
1000 s) by counting the beat note between the two lasers. The
absolute optical frequency of the transition is, for the first time,
determined to be 472851936189.5 kHz by using an optical frequency
comb referenced on the microwave caesium atomic clock. The
uncertainty of the measurement is less than 4.9 kHz. 相似文献
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伴随我国社会经济的持续发展,国家对木材品质的要求越来越高,对木材的需求量也不断提升,木材安全问题已经影响到经济安全。文章结合云南省元谋县国家储备林建设项目,探讨加强国家储备林建设的重要意义,并对加强国家储备林建设的路关径键进词行:设计,在设计路径通过可行性论证后进行实施,从而使国家储备林建设得到有效加强,实现现代林业的高质量发展。 相似文献
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为了提高多模复合导引头跟踪模式复杂逻辑决策的适应性,采用随机森林构建模式决策网络、结合误差补偿的方法,对传统的人工条件判读流程进行了优化,提高了模型的分类准确率,并将该方法应用到复合导引头中进行理论分析和仿真验证。结果表明,得到的跟踪模式的分类正确率达100%,运行速度提升16%,代码量减少3倍; 基于随机森林和误差补偿的跟踪模式决策方法对导引头跟踪模式决策具有较好的适应性,可以高效实现跟踪模式的自主决策。此研究算法为高效率地实现导引头跟踪模式决策提供了参考。 相似文献
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椭圆面积公式S=πab,其中π为圆周率,a、b分别是椭圆半短轴、半长轴的长.关于椭圆面积公式的证法有多种,文献[1]利用仿射变换与仿射不变量推导出椭圆面积公式,文献[2]通过对单位正方形的拉伸(压缩)变换前后面积关系的讨论,给出了椭圆面积公式的又一证法.文献[3]利用初等数学的方法,推导出椭圆面积的计算公式.本文利用投影和定积分知识相结合的方法,给出了任意曲边形面积公式,进而给出椭圆面积公式的一种新的证法. 相似文献
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Thermoelectrics has long been considered as a promising way of power generation for the next decades. So far,extensive efforts have been devoted to the search of ideal thermoelectric materials, which require both high electrical conductivity and low thermal conductivity. Recently, the emerging Dirac semimetal Cd3As2, a three-dimensional analogue of graphene, has been reported to host ultra-high mobility and good electrical conductivity as metals. Here, we report the observation of unexpected low thermal conductivity in Cd3As2, one order of magnitude lower than the conventional metals or semimetals with a similar electrical conductivity, despite the semimetal band structure and high electron mobility. The power factor also reaches a large value of 1.58 m W·m-1·K-2at room temperature and remains non-saturated up to 400 K.Corroborating with the first-principles calculations, we find that the thermoelectric performance can be well-modulated by the carrier concentration in a wide range. This work demonstrates the Dirac semimetal Cd3As2 as a potential candidate of thermoelectric materials. 相似文献