Inclusion agglomeration in electrified molten metal: thermodynamic consideration

The effect of electric current on inclusion agglomeration in molten metal has been investigated. It is found that the agglomeration is dependent on the electric current density, distance between inclusions and orientation of electric field. Electric current retards the agglomeration unless two inclusions are aligned along or closely to the current flow streamlines and the distance between inclusions is less than a critical value. The mechanism is also validated in the computation of cluster agglomeration. The numerical results provide a comprehensive indication for the current-induced inclusion removal and current-induced inclusion elongation. When the inclusions are in long-thin shape, the calculation predicts the current-induced microstructure alignment and current-induced microstructure refinement phenomena

A Body-Nonlinear Green's Function Method with Viscous Dissipation Effects for Large-Amplitude Roll of Floating Bodies

A novel time-domain body-nonlinear Green’s function method is developed for evaluating large-amplitude roll damping of two-dimensional floating bodies with consideration of viscous dissipation effects. In the method, the instantaneous wetted surface of floating bodies is accurately considered, and the viscous dissipation effects are taken into account based on the “fairly perfect fluid” model. As compared to the method based on the existing inviscid body-nonlinear Green’s function, the newly proposed method can give a more accurate damping coefficient of floating bodies rolling on the free surface with large amplitudes according to the numerical tests and comparison with experimental data for a few cases related to ship hull sections with bilge keels

Virtual synchroscope: a novel application of PMU for system restoration

Power system restoration is well recognized as one of the key technologies to improve the reliability of power systems. Generally, the restoration process is divided into several stages as preparation, system restoration, load restoration, synchronization and inter-connection. Currently, re-closure of breakers is done by field crews with synchroscope. A novel methodology, entitled as 'virtual synchroscope', is proposed in this paper. By utilizing Phasor Measurement Units (PMUs), the proposed methodology compares phasors of voltages at connection points from the two islands with the accurately time-stamped measurements. By adjusting voltage magnitude, frequency, and phase angle in the control center, all the requirements for synchronization are satisfied and the synchronization can be implemented. A case study on a power system is presented to validate the feasibility of the proposed method. It is proved that the proposed method can meet the requirements of all standards and resulting in smooth synchronization. © 2011 IEEE.published_or_final_versionThe 2011 International Conference on Advanced Power System Automation and Protection (APAP 2011), Beijing, China, 16-20 October 2011. In Proceedings of APAP, 2011, v. 1, p. 193-19

Construction of system restoration strategy with PMU measurements

This journal issue is the Proceedings of International Conference on Smart Grid and Clean Energy Technologies (ICSGCE 2011)Power system restoration is well-recognized as one of the major technologies to improve system reliability. A high efficient restoration strategy is established and implemented with accurate information acquisition. Phasor measurement unit (PMU) provides a state-of-the-art information monitoring technology. In this paper, with PMU measurements, several algorithms are proposed to ensure complete observability of systems under regular operating conditions and during system restoration process. Case studies on IEEE 14, 30, 57, 118 and 300 - bus systems validate efficiency of the proposed algorithms. © 2011 Published by Elsevier Ltd.postprintThe 2011 IEEE International Conference on Smart Grid and Clean Energy Technologies (IEEE ICSGCE 2011), Chengdu, China, 27-30 September 2011. In Energy Procedia, 2011, v. 12, p. 377-38

Combined fit to BaBar and Belle data on e+e- to pi+pi- psi(2S)

A combined fit is performed to the BaBar and Belle measurements of the e+e- to pi+pi-psi(2S) cross sections for center-of-mass energy between threshold and 5.5 GeV. The resonant parameters of the Y(4360) and Y(4660) are determined. The mass is 4355^{+9}_{-10}\pm 9 MeV/c^2 and the width is 103^{+17}_{-15}\pm 11 MeV/c^2 for the Y(4360), and the mass is 4661^{+9}_{-8}\pm 6 MeV/c^2 and the width is 42^{+17}_{-12}\pm 6 MeV/c^2 for the Y(4660). The production of the Y(4260) in pi+pi-psi(2S) mode is found to be at 2\sigma level, and B(Y(4260) to pi+pi-psi(2S))\Gamma_{e+e-} is found to be less than 4.3 eV/c^2 at the 90% confidence level, or equal to 7.4^{+2.1}_{-1.7} eV/c^2 depending on it interferes with the Y(4360) constructively or destructively. These information will shed light on the understanding of the nature of the Y states observed in initial state radiation processes.Comment: 8 pages, 4 figure

Quantification of Intra-hour Security-constrained Flexibility Region

Rapid growth of renewable energy sources (RES) in the generation capacity mix poses substantial challenges on the operation of power systems in various time scales. Particularly in the intra-hour time scale, the interplay among variability and uncertainty of RES, unexpected transmission/generation outages, and short dispatch lead time cause difficulties in generation-load balancing. This paper proposes a method to quantify the intra-hour flexibility region. A robust security-constrained multi-period optimal power flow (RSC-OPF) model is first constructed to quantify the frequency, magnitude, and intensity of insufficient flexibility. The randomness of RES is captured by uncertainty sets in this model. The N-k contingency, spinning reserve, and corrective control limit constraints are included. This model is then cast into a two-stage robust optimization (RO) model and solved by the column-and-constraint generation (C&CG) method. The emergency measures with a least number of affected buses are derived and subsequently assessed by the post-optimization sensitivity analysis. Finally, the operational flexibility region is determined by continuous perturbation on the RES penetration level and the forecast error. The IEEE 14-bus system and a realistic Chinese 157-bus system are used to demonstrate the proposed method.postprin