This paper proposes a novel and efficient algorithm to obtain the optimal power flow in power system operation and planning phases by solving a multiobjective optimization problem. In deciding the optimal system operation, various objectives, such as economy, reliability and minimum influence on environments, should simultaneously be attained. However, these objectives are contradictory to each other and are in trade-off relations, thus making it difficult to handle this class of problem by conventional approaches which optimizes a single performance index.the optimal load flow problem is first formulated as a multi-objective optimization problem. €-constrained technique is used to obtain a set of non-inferiority solutions. Then, we introduce the idea of a preference index to decide the optimum solution. In this particular study, security index is chosen as the preference index.The proposed algorithm has made it possible to treat the optimal dispatch problems with multiple performance indices and to grasp trade-off relations between selected indices. The effect of uncertain factors pertaining to power systems can also be taken into account.The validity and effectiveness of the proposed approach is verified through numerical examples on the IEEE 30 node, 6 generator system.In the proposed algorithm,
Purpose:To determine the optimal b values required for diffusion-weighted (DW) imaging of the liver in the detection and characterization of benign and malignant hepatic lesions.
Materials and Methods:MR images obtained in 76 patients including 28 malignant hepatic lesions (21 hepatocellular carcinomas and 7 metastases) and 27 benign lesions (12 hemangiomas and 15 cysts) were reviewed. DWecho planner images (EPIs; b values with100, 200, 400, and 800 s/mm 2 ) were reviewed solely first, and then with T2-weighted EPIs (b ϭ 0 s/mm 2 ).Results: Sensitivity for malignant lesions (74%) was highest on DW-EPIs with b value of 100 s/mm 2 and T2-weighted EPIs combined (P Ͻ 0.05), and sensitivity for benign lesions (87%) was highest on DW-EPIs with b value of 800 s/mm 2 and T2-weighted EPIs (P Ͻ 0.05). Specificities were comparably high for all sequences. The Az values for malignant lesions were 0.94, 0.90, 0.87, and 0.89, and those for benign lesions were 0.91, 0.89, 0.87, and 0.94 on DW-EPIs with b values of 100, 200, 400, and 800 and T2-weighted EPIs combined, respectively. Hepatic cysts were clearly distinguished with the cutoff ADC value of 2.5 ϫ10 Ϫ3 mm 2 /s using a b value of 400 s/mm 2 or greater.Conclusion: DW-EPIs with middle b values were not required in the detection and characterization of benign and malignant hepatic lesions.
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