排序方式: 共有20条查询结果,搜索用时 0 毫秒
1.
An indirect laser-induced method for selective removal of large copper areas from a printed circuit board is theoretically and experimentally investigated. The results show that the threshold condition for the process involves phase transition of the epoxy-based substrate resin. Optimal parameters for maximizing process speed are found and discussed. 相似文献
2.
B. Podobnik D. F. Fu H. E. Stanley P. Ch. Ivanov 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(1):47-52
We develop a stochastic process with two coupled variables where
the absolute values of each variable exhibit long-range power-law
autocorrelations and are also long-range cross-correlated. We investigate how
the scaling exponents characterizing power-law autocorrelation and long-range
cross-correlation behavior in the absolute values of the generated variables
depend on the two parameters in our model. In particular, if the
autocorrelation is stronger, the cross-correlation is also stronger. We test
the utility of our approach by comparing the autocorrelation and
cross-correlation properties of the time series generated by our model with
data on daily returns over ten years for two major financial indices, the
Dow Jones and the S&P500, and on daily returns of two well-known
company stocks, IBM and Microsoft, over five years. 相似文献
3.
Podobnik Boris Jusup Marko Wang Zhen Stanley H. Eugene 《Journal of statistical physics》2017,167(3-4):1007-1019
Journal of Statistical Physics - Mutualistic relationships among the different species are ubiquitous in nature. To prevent mutualism from slipping into antagonism, a host often invokes a... 相似文献
4.
Vid Agrež Ferdinand Bammer Boštjan Podobnik Rok Petkovšek 《Applied physics. B, Lasers and optics》2013,112(1):73-81
We present an experimental and numerical analysis, how deviations of the multiplexer-retardation influence the output power of a time-multiplexed dual channel laser. The laser has two different channels, each one with its own gain medium. The channels are time-multiplexed by a single crystal photo-elastic modulator. It enables to double the repetition rate and output power of the laser. However, as multiplexing is based on polarization-switching, the retardation of the modulator should be kept within certain limits. By experimental measurement and theoretical analysis, we determine the operational window within which the retardation should be kept to avoid additional losses into the resonator. The analysis was done for two configurations of the laser setup, namely with and without a quarter-wave plate. 相似文献
5.
A direct spectrographic method for tlic determination of some impurities in UF4 is described. The sample in the graphite electrode was covered with a layer of alumina before the arc was struck; alumina prevents the volatilization of UF4 and thus avoids high spectral and background interferences. To stabilize the discharge, a controlled atmosphere of argon and oxygen was used. The impurity elements were divided into 3 categories according to their volatility: high (B, Si), medium (Co, Mn, V, Mo, Ti, etc.), and low (Ni, Pb, alkaline earths, etc.). Impurities of high and medium volatility could be determined with germanium or aluminum as internal standard. The sensitivities found for this method generally agreed with those of the carrier distillation method. The coefficients of variation varied from 8 to 25% at the 25 p.p.m. level. 相似文献
6.
Summary A method, which involves prior chemical separation of uranium from impurities by tributylphosphate extraction, is described for the determination of alkali metals, alkaline earths and copper in nuclear grade uranium. The characteristic emission lines, excited in hydrogen-oxygen flame, are isolated by a small monochromator and recorded photoelectrically.Using 3 g samples 0.005 ppm of Li, 0.001 ppm of Na, 0.05 ppm of K, 1 ppm of Mg, 1.5 ppm of Ba and 2 ppm of Cu can be determined in uranium, with reproducibilities better than ± 3%.Some interelemental interferences are discussed, and the possibilities of their elimination are described.The method can be used without modification for the analysis of uranium containing up to 100ppm of impurities.
On leave to the IAEA Vienna, Austria. 相似文献
Zusammenfassung Es wird ein Verfahren zur flammenphotometrischen Bestimmung von Alkalien, Erdalkalien und Kupfer in Uran von nuklearem Reinheitsgrad beschrieben, das eine vorherige Extraktion des Urans mit Tributylphosphat verwendet. Die charakteristischen Emissionslinien werden durch eine Wasserstoff-Sauerstoff-Flamme angeregt, durch einen kleinen Monochromator isoliert und photoelektrisch registriert. Mit einer Probe von 3 g können noch 0,005 ppm Li, 0,001 ppm Na, 0,05 ppm K, 1 ppm Mg, 1,5 ppm Ba und 2 ppm Cu mit einer Reproduzierbarkeit von <± 3% bestimmt werden. Störungen durch andere Elemente sowie Möglichkeiten zu ihrer Ausschaltung werden diskutiert. Das Verfahren kann bis zu einem Gehalt von 100 ppm an Verunreinigungen in Uran angewendet werden.
On leave to the IAEA Vienna, Austria. 相似文献
7.
B. Podobnik I. Grosse D. Horvati? S. Ilic P. Ch. Ivanov H. E. Stanley 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,71(2):243-250
In order to quantify the long-range cross-correlations between two time series qualitatively, we introduce a new cross-correlations test QCC(m), where m is the number of degrees of freedom. If there are no cross-correlations between two time series, the cross-correlation
test agrees well with the χ2(m) distribution. If the cross-correlations test exceeds the critical value of the χ2(m) distribution, then we say that the cross-correlations are significant. We show that if a Fourier phase-randomization procedure
is carried out on a power-law cross-correlated time series, the cross-correlations test is substantially reduced compared
to the case before Fourier phase randomization. We also study the effect of periodic trends on systems with power-law cross-correlations.
We find that periodic trends can severely affect the quantitative analysis of long-range correlations, leading to crossovers
and other spurious deviations from power laws, implying both local and global detrending approaches should be applied to properly uncover long-range power-law auto-correlations and cross-correlations
in the random part of the underlying stochastic process. 相似文献
8.
Boris Podobnik Jia Shao Djuro Njavro Plamen Ch. Ivanov H. E. Stanley 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,63(4):547-550
We analyze the dependence of the Gross Domestic Product (GDP) per capita growth rates on changes in the Corruption Perceptions Index (CPI). For the period 1999–2004 for all countries in the world, we find on average that an increase of CPI by one unit leads to an increase of the annual GDP per capita growth rate by 1.7%. By regressing only the European countries with transition economies, we find that an increase
of CPI by one unit generates an increase of the annual GDP per capita growth rate by 2.4%. We also analyze the relation between foreign direct investments received by different countries
and CPI, and we find a statistically significant power-law functional dependence between foreign direct investment per capita and
the country corruption level measured by the CPI. We introduce a new measure to quantify the relative corruption between countries based on their respective wealth as measured
by GDP per capita. 相似文献
9.
How much different genders contribute to citations and whether we see different gender patterns between STEM and non-STEM researchers are questions that have long been studied in academia. Here we analyze the research output in terms of citations collected from the Web of Science of males and females from the largest Croatian university, University of Zagreb. Applying the Mann–Whitney statistical test, for most faculties, we demonstrate no gender difference in research output except for seven faculties, where males are significantly better than females on six faculties. We find that female STEM full professors are significantly more cited than male colleagues, while male non-STEM assistant professors are significantly more cited than their female colleagues. There are ten faculties where females have the larger average citations than their male colleagues and eleven faculties where the most cited researcher is woman. For the most cited researchers, our Zipf plot analyses demonstrate that both genders follow power laws, where the exponent calculated for male researchers is moderately larger than the exponent for females. The exponent for STEM citations is slightly larger than the exponent obtained for non-STEM citations, implying that compared to non-STEM, STEM research output leads to fatter tails and so larger citations inequality than non-STEM. 相似文献
10.
Summary A method for the flame photometric determination of Fe, Ni, Co, Cu, Mn, Al, and Cr in various waters is described. Samples can be analysed directly after removal of interfering anions or after separation (and concentration) of the elements to be determined from any interfering cations. Fe, Ni, Co, and Cu are extracted as carbamates, Al as cupferronate, and Cr as the ion-association complex HCrO3Cl. The extractant used for all is hexone.The elimination of the interference of Mg with Fe is discussed. The variation of the relative error of the emission measurement with the concentration of the elements was investigated.
Paper presented at the Symposium on Analytical Chemistry, Graz, 29th September–1st October 1965. 相似文献
Zusammenfassung Eine Methode zur flammenphotometrischen Bestimmung von Fe, Ni, Co, Cu, Mn, Al und Cr in Wässern wurde beschrieben. Nach Entfernung der störenden Anionen oder nach Abtrennung (und Anreicherung) der zu bestimmenden Elemente von etwa störenden Kationen können die Proben direkt analysiert werden. Fe, Ni, Co und Cu werden als Carbamate extrahiert, Al als Cupferronat und Cr in Form des Ionen-Assotiationskomplexes HCrO3Cl. Als Extraktionsmittel dient in allen Fällen Hexon.Die Beseitigung des störenden Einflusses von Magnesium bei der Eisenbestimmung wurde diskutiert. Die Variation des relativen Fehlers der Emissionsmessung mit der Konzentration der Elemente wurde untersucht.
Résumé On décrit une méthode pour le dosage par photométrie de flamme du Fe, Ni, Co, Cu, Mn, Al et Cr dans des eaux variées. On peut faire l'analyse directe après élimination des anions qui interfèrent ou après séparation (et concentration) des éléments à doser d'avec les cations gênants. On extrait Fe, Ni, Co et Cu sous forme de carbamates, Al en cupferronate, et Cr à l'état de complexe par association ionique, HCrO3Cl. Dans tous les cas, on utilise l'hexone comme agent d'extraction.On discute l'élimination de l'interférence du Mg par le Fe. On a suivi la variation de l'erreur relative dans la mesure de l'émission en fonction de la concentration des éléments.
Paper presented at the Symposium on Analytical Chemistry, Graz, 29th September–1st October 1965. 相似文献