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111.
112.
旋转对称非球面自动加工控制算法研究 总被引:1,自引:0,他引:1
介绍了计算机控制光学表面成型(CCOS) 技术的基本原理,对双旋转磨头的去除函数进行研究,研究了不同形状的磨头的去除函数特性,并在多次实验的基础上得到了最优的加工参数,在去除函数的基础上提出了模板函数的概念及算法。根据加工旋转对称非球面光学表面的特点,结合模板函数提出了一种基于同心圆磨头运动轨迹的控制算法。运用该算法对神光Ⅲ号打靶非球面透镜的一种工艺试样( Φ300m m ,F5-9 ,最大非球面度为46μm) 进行自动加工,面型精度达到1λ(RMS,λ= 632-8nm),取得了满意的结果。 相似文献
113.
马来酸酐溶液法接枝无规聚丙烯的研究 总被引:10,自引:0,他引:10
采用溶液法选用极性单体马来酸酐,在非隔氧条件下,对无规聚丙烯进行接枝改性。考察了不同温度、引发剂浓度、反应时间等因素对产物接枝率的影响,并用正交法指出影响因素的显著性,确定了控制MAPP接枝率的主要参数,找出了合成马来酸酐接枝无规聚丙烯(MAPP)的方法、体系与条件。采用红外及化学滴定等方法对聚合物的接枝率和结构进行了表征,证实了实验结果及相关理论的解释。 相似文献
114.
铑(Ⅲ)—碱性染料—高碘酸钾催化光度法测定痕量铑 总被引:3,自引:0,他引:3
在氯化钠-磷酸溶液中,铑(Ⅲ)催化高碘酸钾氧化碱性染料(乙基罗丹明B,丁基罗丹明B,耐尔蓝)褪色,反应速率与铑浓度呈线性的范围依次为02~40,0~45和0~60μg/25mL,检出限依次为224×10-10,284×10-10和380×10-10g/mL.本催化反应对铑(Ⅲ)或碱性染料均为一级反应.催化反应的表观活化能分别为6521,6341和6101kJ/mol.考察了40多种共存离子的影响,Os,Ru,Ir干扰,其它贵金属、有色金属和铁不干扰.题示体系已用于某些催化剂和冶金产品中痕量铑的测定,结果满意 相似文献
115.
Uwe Schning 《Random Structures and Algorithms》2000,17(1):64-77
We show the existence of various versions of expander graphs using Kolmogorov complexity. This method seems superior to the usual probabilistic construction. It turns out that the best known bounds on the size of expanders and superconcentrators can be attained based on this method. In the case of (acyclic) superconcentrators we attain a density of about 34 edges/vertices. Furthermore, related graph properties are reviewed, like magnification, edge‐magnification, and isolation, and we develop bounds based on the Kolmogorov approach. © 2000 John Wiley & Sons, Inc. Random Struct. Alg., 17: 64–77, 2000 相似文献
116.
Reactions at the Metallic Substrate: Single Crystals of Ni(NH3)2V2F8 Except for the main product (NH4)2[TaF7] and some [Ni(NH3)6][TaF6]2, the new light green Ni(NH3)2V2F8 is obtained by the reaction of (NH4)F with tantalum and vanadium (molar ratio of (NH4)F : Ta : V = 36 : 6 : 1) at 400 °C in a sealed Monel ampoule (Cu32Ni68). The crystal structure (orthorhombic, Fmmm, Z = 4, a = 752.9(1), b = 762.9(1), c = 1307.6(2) pm) is related to that of (NH4)[VF4]. According to {Ni(NH3)2}0,5[VF4], corrugated layers of vertex-connected octahedra [VF4/2F2/1] are stacked in the [001] direction. Between these layers trans-{Ni(NH3)2} units are inserted so that Ni2+ enhances its coordination number to 6 by two times two F– from the layers above and below. 相似文献
117.
加速溶剂萃取-GPC纯化-气相色谱-质谱法测定油区土壤中的种多环芳烃 《山东科学》2015,28(2):81-86
为了排除背景干扰,使测定数据更加准确,先通过加速溶剂萃取和GPC纯化方法富集油区土壤中约16种多环芳烃, 再借助于气相色谱 质谱建立了高效、准确的分析方法。该方法对16种多环芳烃的相关系数在0.997以上,检出限为0.8~7.3 ng/mL,回收率为82.8%~94.2%,相对标准偏差为1.38%~8.86%。对实际样品的分析检测结果表明,本方法在油区土壤中的多环芳烃分析方面值得推广。 相似文献
118.
Willi A. Brand Tyler B. Coplen Anita T. Aerts‐Bijma J. K. Böhlke Matthias Gehre Heike Geilmann Manfred Gröning Henk G. Jansen Harro A. J. Meijer Stanley J. Mroczkowski Haiping Qi Karin Soergel Hilary Stuart‐Williams Stephan M. Weise Roland A. Werner 《Rapid communications in mass spectrometry : RCM》2009,23(7):999-1019
Internationally distributed organic and inorganic oxygen isotopic reference materials have been calibrated by six laboratories carrying out more than 5300 measurements using a variety of high‐temperature conversion techniques (HTC) a in an evaluation sponsored by the International Union of Pure and Applied Chemistry (IUPAC). To aid in the calibration of these reference materials, which span more than 125‰, an artificially enriched reference water (δ18O of +78.91‰) and two barium sulfates (one depleted and one enriched in 18O) were prepared and calibrated relative to VSMOW2 b and SLAP reference waters. These materials were used to calibrate the other isotopic reference materials in this study, which yielded:
The seemingly large estimated combined uncertainties arise from differences in instrumentation and methodology and difficulty in accounting for all measurement bias. They are composed of the 3‐fold standard errors directly calculated from the measurements and provision for systematic errors discussed in this paper. A primary conclusion of this study is that nitrate samples analyzed for δ18O should be analyzed with internationally distributed isotopic nitrates, and likewise for sulfates and organics. Authors reporting relative differences of oxygen‐isotope ratios (δ18O) of nitrates, sulfates, or organic material should explicitly state in their reports the δ18O values of two or more internationally distributed nitrates (USGS34, IAEA‐NO‐3, and USGS35), sulfates (IAEA‐SO‐5, IAEA‐SO‐6, and NBS 127), or organic material (IAEA‐601 benzoic acid, IAEA‐602 benzoic acid, and IAEA‐600 caffeine), as appropriate to the material being analyzed, had these reference materials been analyzed with unknowns. This procedure ensures that readers will be able to normalize the δ18O values at a later time should it become necessary. The high‐temperature reduction technique for analyzing δ18O and δ2H is not as widely applicable as the well‐established combustion technique for carbon and nitrogen stable isotope determination. To obtain the most reliable stable isotope data, materials should be treated in an identical fashion; within the same sequence of analyses, samples should be compared with working reference materials that are as similar in nature and in isotopic composition as feasible. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
Reference material | δ18O and estimated combined uncertainty c |
---|---|
IAEA‐602 benzoic acid | +71.28 ± 0.36‰ |
USGS35 sodium nitrate | +56.81 ± 0.31‰ |
IAEA‐NO‐3 potassium nitrate | +25.32 ± 0.29‰ |
IAEA‐601 benzoic acid | +23.14 ± 0.19‰ |
IAEA‐SO‐5 barium sulfate | +12.13 ± 0.33‰ |
NBS 127 barium sulfate | +8.59 ± 0.26‰ |
VSMOW2 water | 0‰ |
IAEA‐600 caffeine | ?3.48 ± 0.53‰ |
IAEA‐SO‐6 barium sulfate | ?11.35 ± 0.31‰ |
USGS34 potassium nitrate | ?27.78 ± 0.37‰ |
SLAP water | ?55.5‰ |
119.
Auwärter W Weber-Bargioni A Riemann A Schiffrin A Gröning O Fasel R Barth JV 《The Journal of chemical physics》2006,124(19):194708
We present a low-temperature scanning tunneling microscopy (STM) study on the supramolecular ordering of tetrapyridyl-porphyrin (TPyP) molecules on Ag(111). Vapor deposition in a wide substrate temperature range reveals that TPyP molecules easily diffuse and self-assemble into large, highly ordered chiral domains. We identify two mirror-symmetric unit cells, each containing two differently oriented molecules. From an analysis of the respective arrangement it is concluded that lateral intermolecular interactions control the packing of the layer, while its orientation is induced by the coupling to the substrate. This finding is corroborated by molecular mechanics calculations. High-resolution STM images recorded at 15 K allow a direct identification of intramolecular features. This makes it possible to determine the molecular conformation of TPyP on Ag(111). The pyridyl groups are alternately rotated out of the porphyrin plane by an angle of 60 degrees. 相似文献
120.
J. Brüning S. Yu. Dobrokhotov D. S. Minenkov 《Russian Journal of Mathematical Physics》2014,21(1):1-8
As in the first part (J. Brüning, S.Yu. Dobrokhotov, D.S. Minenkov, 2011), we construct a family of special solutions of the Dirichlet problem for the Laplace equation in a domain with fast changing boundary. Using these solutions, we construct an analytic model of cold field electron emission from surfaces simulating arrays of vertically aligned nanotubes. Explicit analytic formulas lead to fast computations and also allow us to study the case of random arrays of tubes with stochastic distribution of parameters. We present these results and compare them with numerical approximations given in [1]. 相似文献