Quantitative Determination of phosphatidylcholine by an HPLC-RI system

The following describes the quantitative determining method for phosphatidylcholine (PC) using the HPLC-RI system which we have developed. It uses Lichromsorb, Si 60 (10 μm), 4.6 mm × 250 mm as the column and a mobile phase consisting of n-hexane/isopropanol/water =1:4:1. In this report, we compared data from selected high-purity (60–100 wt%) samples using the HPLC-RI, HPLC-UV and conventional TLC-P methods. Under the conditions we described, the HPLC-UV method was somewhat affected by fatty acid compositions. As a result, there were some inconsistencies in the measured values. However, the HPLC-RI method we propose was applicable to PC from both egg yolk and soybeans. In addition, the HPLC-RI method produced data which correlated well with data from the TLC-P method, and this data was highly accurate and exhibited satisfac-tory reproductibility.     

Eigenvalue estimation of dominant electromechanical modes based on synchronous measurement and generator grouping technique

The authors have been studying a new approach for modal analysis of large power systems that utilizes GPS‐based synchronous measurement technology. The approach is based on the identification of a linearized multi‐input multi‐output model of power system. Since the identified model expresses approximately the electromechanical dynamics of an actual power system, modal frequencies, dampings, and mode shapes corresponding to electromechanical modes can be estimated as eigenvalues and eigenvectors of the identified model. In the paper, in order to advance our approach to a practical technique, it is mainly discussed how to select a small number of machines suitable for measurement locations to estimate eigenvalues associated with dominant slow modes. Such machines can be detected by identifying coherent groups related to the slow modes. The reference generators that behave representatively in each coherent group are the optimal ones to be measured. Therefore, the slow modes can be obtained by observing one generator from each group. The verification of the new modal analysis and coherency‐based machine selection is done through simulation studies using the IEEJ EAST 10‐machine system model. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 164(4): 24–32, 2008; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20428