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121.
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123.
S. A. Soliman S. E. A. Eman G. S. Christensen 《Journal of Optimization Theory and Applications》1990,65(2):305-319
Loads on electric utility systems have two components: active power (measured in kilowatts) and reactive power (measured in kilovars). Active power has to be generated at the power plant, whereas reactive power can be provided by either power plants or capacitors. It is a well-known fact that shunt power capacitors are the most economical source to meet the reactive power requirements of inductive loads and transmission lines operating at a lagging power factor.This paper describes new contributions to the problem of optimization of size and control setting of shunt capacitors on distribution feeders, so that the losses along the feeder are minimized. The variation of the KVAR of the load on the feeder with the distance from the substation is assumed to be linear. The parameters of this function are estimated from the available KVAR loading on the feeder first by using least-square techniques and then by using least-absolute-value parameter estimation techniques. The results obtained are compared with that obtained if the current profile is assumed to be uniformly distributed on the feeder. Our results show that the optimum size of the capacitor bank as well as its optimum location depend on the parameters of the model used for the load. Also, our results show a large saving in the size of the capacitor banks used with a considerable per-unit-loss reduction along the feeder.This work was supported by the National Science and Engineering Research Council of Canada, Grant No. A4146. The first author acknowledges the help received from Engineer Samy Soliman for reviewing all the mathematical expressions in this paper. 相似文献
124.
A high-performance liquid chromatographic method for the determination of 2-naphthylamine in urine using fluorescence detection was developed. The method validation analysis showed the method to be in analytical control, i.e. the distribution of the difference between the observed and true values of the method evaluation samples did not deviate significantly from the normal distribution. The recovery of the method was 85%. The entire run time of chromatography was 10 min using isocratic elution (acetonitrile-water, 35:65), and the retention time for 2-naphthylamine was 5.8 min. The relative short time of analysis in combination with the low limit of detection (0.272 nmol/l) makes the method potentially applicable for surveillance of occupational and environmental exposure to 2-nitronaphthalene. The developed method is presently used for measurement of 2-naphthylamine in urine samples from workers employed at factories, characterized by a low airborne exposure level of polycyclic aromatic hydrocarbons, i.e. in general less than 25 micrograms/m3. The urine samples of exposed workers (n = 95) showed a 2-naphthylamine range of up to 9.4 nmol/l, whereas unexposed control individuals (n = 114) showed a range of up to 0.87 nmol/l. 相似文献
125.
J. Molin Christensen 《Fresenius' Journal of Analytical Chemistry》1987,326(7):656-657
Summary Valuable information can be obtained at little expenses from quality control samples prepared in-house to monitor the determination of blood lead by atomic absorption spectrophotometry. Commercially manufactured control materials can also be used for this purpose. These materials are compared to standard reference materials which at present are available.The relative standard deviations for analysis of NBS standard reference materials were 15.4–2.8% (range 60–754 g/l) and in agreement with the relative standard deviation estimated for the analytical method. The corresponding figures for BCR control reference materials were lower: 1.1–1.4% (range 134–795 g/l).The average analytical bias demonstrated by analysis of NBS standard reference material and BCR control reference material were 3–6% (range 795–60 g/l) and in agreement with bias estimated by analysis of commercially manufactured and in-house prepared control materials. 相似文献
126.
Reed M. Izatt Don W. McBride James J. Christensen Jerald S. Bradshaw Glen A. Clark 《Journal of membrane science》1985,22(1):31-46
Carrier-mediated cation fluxes were determined using a H2OCHC13H2O liquid merebrane system for TlNO3 and for binary mixtures of either TlNO3 or KNO3 with alkali metal ions, alkaline earth metal ions, and Pb2+ (in the case of TlNO3). Both macrocyclic polyether and cryptand ligands were used as carriers. In Tl+Mn+ mixtures, selective transport of Tl+ was found over all cations studied, except in the cases of Ag+ by 2.2 and of Pb2+ by 18C6, DC18C6, ClDKP18C6, and 2.2. Generally, K+ was transported selectively from K+Mn+ mixtures, except in the cases of K+Tl+ mixtures in which Tl+ was transported selectively in all cases. A model relating cation flux to log K(CH3OH) for Mn+—macrocycle interaction and to ion-partitioning between the organic and aqueous phases was successful in rationalizing selective cation transport in most of the systems studied. 相似文献
127.
Niels M. Christensen 《manuscripta mathematica》1977,20(3):255-262
Let f be a C∞-function satisfying a Lojasiewicz-inequality. Is it possible that the Taylor series of f is the zero-series in some point? We will show here that this is not possible. 相似文献
128.
P. A. P. Lindberg L. I. Johansson A. N. Christensen 《Zeitschrift für Physik B Condensed Matter》1988,69(4):521-527
Angle-resolved photoemission measurements have been performed on the (110) face of a VC0.80 single crystal using resonance radiation. A vacancy-induced peak is identified at about 1.7 eV below the Fermi energy. Comparison of the experimental peak dispersions with direct transitions between energy bands of VC1.0 is also made. 相似文献
129.
Total syntheses of 1α- and 1β-methyl thienamycin are reported. 1β-Methyl thienamycin retains the antibacterial activity of thienamycin and is highly resistant to hydrolysis by DHP-I enzyme. 相似文献
130.
Erik Christensen 《Journal of Functional Analysis》1978,27(2):234-247
Any derivation of a properly infinite von Neumann algebra on a Hilbert space into the algebra of bounded operators on this space is implemented by a bounded operator. 相似文献