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排序方式: 共有813条查询结果,搜索用时 31 毫秒
31.
D R Thielen G Olsen A Davis E Bajor J Stefanovski J Chodkowski 《Journal of chromatographic science》1987,25(1):12-16
Microextraction and capillary-column gas chromatography techniques are applied to plant discharge streams for repetitive wastewater discharge permit analyses. This combination allows the analyst to reduce sample preparation since microextraction replaces both purge-and-trap for volatiles and microextraction for semi-volatiles. An additional advantage is the elimination of a concentration step, which is often a major contributor to low method recoveries. The overall procedure is shown to be more precise than purge-and-trap but slightly less precise than conventional extraction. The results of each method are shown to be equivalent. 相似文献
32.
H. Schmalfuß H. Werner G. Curli T. P. Hilditch H. E. Longenecker Fr. Kiermeier Fr. X. Maier C. I. Kruisheer P. C. den Herder G. Roeder B. Segal A. Romeo V. Crupi G. Dorta G. Lunde H. Kringstad E. Mathiesen A. Olsen F. N. Woodward S. R. Hoover S. Schmidt-Nielsen und J. Stone 《Fresenius' Journal of Analytical Chemistry》1941,121(1-2):55-59
Ohne Zusammenfassung 相似文献
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35.
Benjamin Debrus Pierre Lebrun Attilio Ceccato Gabriel Caliaro Bernadette Govaerts Bernard A. Olsen Eric Rozet Bruno Boulanger Philippe Hubert 《Talanta》2009,79(1):77-85
One of the major issues within the context of the fully automated development of chromatographic methods consists of the automated detection and identification of peaks coming from complex samples such as multi-component pharmaceutical formulations or stability studies of these formulations. The same problem can also occur with plant materials or biological matrices. This step is thus critical and time-consuming, especially when a Design of Experiments (DOE) approach is used to generate chromatograms. The use of DOE will often maximize the changes of the analytical conditions in order to explore an experimental domain. Unfortunately, this generally provides very different and “unpredictable” chromatograms which can be difficult to interpret, thus complicating peak detection and peak tracking (i.e. matching peaks among all the chromatograms). In this context, Independent Components Analysis (ICA), a new statistically based signal processing methods was investigated to solve this problem. The ICA principle assumes that the observed signal is the resultant of several phenomena (known as sources) and that all these sources are statistically independent. Under those assumptions, ICA is able to recover the sources which will have a high probability of representing the constitutive components of a chromatogram. In the present study, ICA was successfully applied for the first time to HPLC–UV-DAD chromatograms and it was shown that ICA allows differentiation of noise and artifact components from those of interest by applying clustering methods based on high-order statistics computed on these components. Furthermore, on the basis of the described numerical strategy, it was also possible to reconstruct a cleaned chromatogram with minimum influence of noise and baseline artifacts. This can present a significant advance towards the objective of providing helpful tools for the automated development of liquid chromatography (LC) methods. It seems that analytical investigations could be shortened when using this type of methodologies. 相似文献
36.
Min Wen Gilbert Laporte Oli B G Madsen Anders V Nørrelund Allan Olsen 《The Journal of the Operational Research Society》2014,65(10):1555-1561
Environment-friendly electric vehicles have gained popularity and increased attention in recent years. The deployment of a network of recharging stations is essential given their limited travel range. This paper considers the problem of locating electronic replenishment stations for electric vehicles on a traffic network with flow-based demand. The objective is to optimize the network performance, for example to maximize the flow covered by a prefixed number of stations or to minimize the number of stations needed to cover traffic flows. Two integer linear programming formulations are proposed to model the problem. These models are tested on real-life traffic data collected in Denmark. 相似文献
37.
The VF3-type compounds MF3 with M = Fe and Ga have been studied by high-pressure energy-dispersive X-ray diffraction. The compression mechanism was found to be highly anisotropic for both compounds, with the c-axis showing little pressure dependence. The volume reduction is mainly achieved through coupled rotations of the MF6 octahedra around the c-axis, which reduces the length of the a-axis. The compression mechanism of both compounds is reasonably well described in terms of deformation of an 8/3/c2 sphere-packing model up to the pressures where the fluorine atoms become hexagonally close-packed. It is proposed that both compounds enter a phase with the fluorine atom arranged in a “super-dense” sphere packing at higher pressures. The zero pressure bulk modulus of FeF3 and GaF3 was determined as 12(2) and 37(3) GPa, respectively, and a scaling relation between the zero pressure bulk modulus and unit cell volumes was found for TiF3, CrF3, FeF3 and GaF3. 相似文献
38.
Abstract High—pressure crystal structure studies have been performed on Sm up to 100 GPa using synchrotron x-radiation and a diamond anvil cell. The structural sequence Sm-dhcp-fcc-dist.fcc has been confirmed. There is no evidence of any volume collapse. The bulk modulus and its pressure derivative have been determined (B0 = 30.7 GPa, B0’ = 2.5). 相似文献
39.
Abstract The high-pressure crystal structures of the compounds UX, where X = N, P, As and Sb, have been studied using X-ray diffraction in the pressure range up to about 60 GPa Rhornbohedral distortions are observed for UN and Up above 29 GPa and lO GPa, respectively. In Up a further transformation to an orthorhombic phase occurs at 28 GPa. UAs and USb transform to the CsCl structure at 20 GPa and 9 GPa, respectively. The latter transformations show a considerable hysteresis when the pressure is released. The scaling behaviour of the bulk modulus has been studied. It is confirmed that a log-log plot of bulk modulus versus specific volume for the cubic phases gives a straight line with a slope near ? 5/3. 相似文献
40.
Yoichi Sakai Ryo Omatsuzawa Iwao Sakazaki Sayaka Suzuki Hayato Hashino Takanobu Saito Takahiko Iriyama 《Hyperfine Interactions》2005,166(1-4):483-487
Samarium–iron intermetallic compounds were prepared by a melt spinning method with low and high wheel speeds, which resulted in a Th2Zn17-type and a TbCu7-type structure, respectively. Structure comparison between these types was investigated for Sm–Fe intermetallic compounds and their nitrides by 57Fe-Mössbauer spectroscopy. 相似文献