排序方式: 共有34条查询结果,搜索用时 125 毫秒
1.
2.
5-(5-氯-2-吡啶偶氮)-2,4-二氨基甲苯分光光度法测定微量钌(Ⅲ) 总被引:4,自引:0,他引:4
研究了 5- ( 5-氯 - 2 -吡啶偶氮 ) - 2 .4-二氨基甲苯 ( 5- Cl- PADAT)与钌 ( )的显色反应。在 p H4.0~ 6.5HAc- Na Ac缓冲溶液中 ,在加热的条件下 ,5- Cl-PADAT与 Ru( )形成稳定的配合物 ,加入无机酸 ( HCl,HCl O4 ,H2 SO4 ,H3 PO4 )酸化后 ,其最大吸收波长位于 50 5nm处 ,表观摩尔吸光系数为 8.5×1 0 4 L· mol-1· cm-1,钌浓度在 0~ 6μg/ 1 0 m L范围内服从比耳定律 ,Ru( )与 5- Cl- PADAT配合物的摩尔比为 1∶ 2。以 EDTA为掩蔽剂 ,方法具有良好的选择性 ,已应用于合成样中钌的测定。 相似文献
3.
4.
利用金属有机气相外延方法研究了非故意掺杂GaN薄膜的方块电阻与高温GaN体材料生长时载气中N2比例的关系.研究发现,随着载气中N2比例的增加,GaN薄膜方块电阻急剧增加.当载气中N2比例为50%时,GaN薄膜方块电阻达1.1×108Ω/□,且GaN表面平整,均方根粗糙度为0.233nm.二次离子质谱分析发现,载气中N2比例不同的样品中碳、氧杂质含量无明显差别.随着载气中N2比
关键词:
半绝缘GaN薄膜
载气
金属有机气相外延
位错 相似文献
5.
转象光学系统有一对固定且同轴安装的透镜。本文提出的一般法则是用一对透镜替换转象系统中的任一元件。这一法则能够反复使用,从而使系统有多种变化形式。文中的典型用途说明了该系统的设计问题。 相似文献
6.
A dedicated breast CT system (DBCT) is a new method for breast cancer detection proposed in recent years. In this paper, the glandular dose in the DBCT is simulated using the Monte Carlo method. The phantom shape is half ellipsoid, and a series of phantoms with different sizes, shapes and compositions were constructed. In order to optimize the spectra, monoenergy X-ray beams of 5-80 keV were used in simulation. The dose distribution of a breast phantom was studied: a higher energy beam generated more uniform distribution, and the outer parts got more dose than the inner parts. For polyenergtic spectra, four spectra of Al filters with different thicknesses were simulated, and the polyenergtic glandular dose was calculated as a spectral weighted combination of the monoenergetic dose. 相似文献
7.
关于某些参数对原子吸收喷雾速率的影响,通常应用流体力学的Poiseuille公式(Q_1=πR~4ΔP/3ηL)来描述。但是目前的文献对公式中ΔP的解释尚欠具体和统一。诸如压力、有效压力差、引起液体流动的压力、溶液对毛细管内壁的有效压力等,这些解释都没有明确而具体地反映原子吸收雾化过程的实际情况。目前更无深入研究ΔP对喷雾速率Q_1影响的报导。本文根据流体力学的基本原理和原子吸收雾化过程的实 相似文献
8.
Beam hardening correction for a cone-beam CT system and its effect on spatial resolution 总被引:1,自引:0,他引:1
In this paper, we present a beam hardening correction (BHC) method in three-dimension space for a cone-beam computed tomography (CBCT) system in a mono-material case and investigate its effect on the spatial resolution. Due to the polychromatic character of the X-ray spectrum used, cupping and streak artifacts called beam hardening artifacts arise in the reconstructed CT images, causing reduced image quality. In addition, enhanced edges are introduced in the reconstructed CT images because of the beam hardening effect. The spatial resolution of the CBCT system is calculated from the edge response function (ERF) on different planes in space. Thus, in the CT images with beam hardening artifacts, enhanced ERFs will be extracted to calculate the modulation transfer function (MTF), obtaining a better spatial resolution that deviates from the real value. Reasonable spatial resolution can be obtained after reducing the artifacts. The 10% MTF value and the full width at half maximum (FWHM) of the point spread function with and without BHC are presented. 相似文献
9.
Luminescence properties of InxGa1-xN(x~0.04) films grown by metal organic vapour phase epitaxy 下载免费PDF全文
In x Ga 1-x N (x ~ 0.04) films are grown by metal organic vapour phase epitaxy.For the samples grown on GaN directly,the relaxation of InGaN happens when its thickness is beyond a critical value.A broad band is observed in the luminescence spectrum,and its intensity increases with the increasing degree of relaxation.Secondary ion mass spectrometry measurement rules out the possibility of the broad band originating from impurities in InGaN.The combination of the energy-dispersive X-ray spectra and the cathodeluminescence measurements shows that the origin of the broad band is attributed to the indium composition inhomogeneity caused by the phase separation effect.The measurement results of the tensile-strained sample further demonstrate the conclusions. 相似文献
10.
利用金属有机气相外延方法研究了非故意掺杂GaN薄膜的方块电阻与高温GaN体材料生长时载气中N2比例的关系.研究发现,随着载气中N2比例的增加,GaN薄膜方块电阻急剧增加.当载气中N2比例为50%时,GaN薄膜方块电阻达1.1×108Ω/□,且GaN表面平整,均方根粗糙度为0.233 nm.二次离子质谱分析发现,载气中N2比例不同的样品中碳、氧杂质含量无明显差别.随着载气中N2比例的增加,GaN材料中螺型位错相关缺陷密度无明显变化,而刃型位错相关缺陷密度明显增加.结果表明,刃型位错的受主补偿作用是导致GaN薄膜方块电阻变化的主要原因. 相似文献