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Search Results: 1 - 10 of 21391 matches for " Eung-Bo Sim "
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Stability Enhancement in HVDC System with STATCOM  [PDF]
Chan-Ki Kim, Jin-Young Kim, Sung-Doo Lee, Eung-Bo Sim
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.311133
Abstract: This paper deals with the stability problem at the inverter end of a HVDC link with STATCOM (Static Compensator), when connected to a weak AC system which has the stability enhancement for power instability and commutation failures. The HVDC stability problem is tackled with a STATCOM which not only provides a rapid recovery from power, harmonic stability and commutation failures but also offers a lower cost filter design for the HVDC system. PSCAD/EMTDC simulations are presented to demonstrate the robust performance and to validate the proposed topology.
Identification of Acceptable Restoration Strategies
Seung-Tae Cha,Nam-Ho Lee,Eung-Bo Shim,Jeong-Hoon Shin
Journal of Systemics, Cybernetics and Informatics , 2008,
Abstract: In recent years, we have seen several catastrophic and cascading failures of power systems throughout the world. Power system breakup and blackouts are rare events. However, when they occur, the effects on utilities and general population can be quite severe. To prevent or reduce cascading sequences of events caused by the various reasons, KEPRI is researching ways to revolutionize innovative strategies that will significantly reduce the vulnerability of the power system and will ensure successful restoration of service to customers. This paper describes a restoration guidelines / recommendations for the KEPS simulator, which allows power system operator and planner to simulate and plan restoration events in an interactive mode. The KEPS simulator provides a list of restoration events according to the priority based on some restoration rules and list of priority loads. Further, the paper will draw on research using information from a Jeju case study.
Gauged R-symmetry, Fermion and Higgs Mass Problem
Eung Jin Chun
Physics , 1995, DOI: 10.1016/0370-2693(95)01486-1
Abstract: We consider the simplest model of $SU(3) \times SU(2) \times U(1)_Y \times U(1)_R$ gauge symmetry with one extra singlet field whose vacuum expectation value breaks the horizontal $R$-symmetry $U(1)_R$ and gives rise to Yukawa textures. The $U(1)_R$ symmetry is able to provide both acceptable fermion mass hierarchies and a natural solution to the $\mu$ problem only if its mixed anomalies are cancelled by the Green-Schwarz mechanism. When the canonical normalization $g_3^2=g_2^2={5\over3}g_1^2$ of the gauge coupling constants is assumed, the Higgs mass parameter $\mu \sim m_{3/2}$ can arise taking into acount the uncertainty in the ultraviolet relation $m_e m_\mu m_\tau/m_d m_s m_b \simeq \lambda^q$ with $q \neq 0$. When $q=0$ is taken only a suppressed value of $\mu \sim \lambda m_{3/2}$ can be obtained.
Axino-Neutrino Mixing in Gauge-Mediated Supersymmetry Breaking Models
Eung Jin Chun
Physics , 1999, DOI: 10.1016/S0370-2693(99)00351-2
Abstract: When the strong CP problem is solved by spontaneous breaking of an anomalous global symmetry in theories with gauge-mediated supersymmetry breaking, the pseudo Goldstone fermion (the axino) is a good candidate of a light sterile neutrino. Its mixing with neutrinos relevant for current neutrino experiments can arise in the presence of R-parity violation. The realistic four neutrino mass matrix is obtained when the see-saw mechanism is brought in, and an ansatz for the right-handed neutrino mass is constructed.
Minimal Dark Matter and Leptogenesis
Eung Jin Chun
Physics , 2011, DOI: 10.1007/JHEP03(2011)098
Abstract: A Dirac fermion carrying an integral weak isospin and the vanishing hypercharge is considered as its neutral component can be a promising dark matter candidate (called the minimal dark matter) whose mass is of order 100 GeV. While the symmetric population annihilates away due to a rapid gauge interaction, its asymmetric abundance is supposed to be produced by the decay of a right-handed neutrino superfield in the supersymmetric type I seesaw mechanism. The efficiencies for generating the dark matter and lepton asymmetries are calculated by solving a set of approximate Boltzmann equations. A spectacular feature of this scenario is the existence of a long-lived singly- or multiply-charged scalar and a shorter-lived singly-charged fermion whose tracks can be readily looked for at the LHC.
CP Violation, Sneutrino Oscillation and Neutrino Masses in R-parity Violating Supersymmetric Standard Model
Eung Jin Chun
Physics , 2001, DOI: 10.1016/S0370-2693(01)01436-8
Abstract: In supersymmetric theories, sneutrino--anti-sneutrino mixing can occur with the oscillation time $\sim 0.01$ ps corresponding the atmospheric neutrino mass scale $\sim 0.05$ eV. We explore the possibility of observing sneutrino oscillation phenomena and CP violation when R-parity violation explains the observed neutrino masses and mixing. It is shown for some parameter region in the bilinear model of R-parity violation that the tiny sneutrino mass splitting and time-dependent CP violating asymmetries could be measured in the future experiments if the tau sneutrino is the lightest supersymmetric particle.
Strong CP and Mu Problems in Theories with Gauge Mediated Supersymmetry Breaking
Eung Jin Chun
Physics , 1997, DOI: 10.1103/PhysRevD.59.015011
Abstract: We provide a simple solution to the $\mu$ and strong CP problems in the context of gauge mediated supersymmetry breaking. The generic appearance of R symmetry in dynamical supersymmetry breaking is used to implement Peccei-Quinn symmetry. Acceptable $\mu$ and $B$ terms as well as the large symmetry breaking scale are induced in the presence of nonrenormalizable interactions. Cosmological consequences of this scheme turn out to yield constraints on the PQ symmetry breaking scale and the number of the messenger/heavy quarks. Complexity in introducing non-R Peccei-Quinn symmetry is contrasted with the case of R symmetry.
R-parity Violation and Neutrino Masses
Eung Jin Chun
Physics , 2000,
Abstract: R-parity violation in the supersymmetric standard model could be the origin of neutrino masses and mixing accounting for the atmospheric and solar neutrino oscillations. More interestingly, this hypothesis may be tested in future colliders by detecting lepton number violating decays of the lightest supersymmetric particle. Here, we present a comprehensive analysis for the determination of sneutrino vacuum expectation values from the one-loop effective scalar potential, and also for the one-loop renormalization of neutrino masses and mixing. Applying our results to theories with gauge mediated supersymmetry breaking, we discuss the effects of the one-loop corrections and how the realistic neutrino mass matrices arise.
Leptogenesis origin of Dirac gaugino dark matter
Eung Jin Chun
Physics , 2010, DOI: 10.1103/PhysRevD.83.053004
Abstract: The Dirac nature of the gauginos (and also the Higgsinos) can be realized in $R$-symmetric supersymmetry models. In this class of models, the Dirac bino (or wino) with a small mixture of the Dirac Higgsinos is a good dark matter candidate. When the seesaw mechanism with Higgs triplet superfields is implemented to account for the neutrino masses and mixing, the leptogenesis driven by the heavy triplet decay is shown to produce not only the matter-antimatter asymmetry but also the asymmetric relic density of the Dirac gaugino dark matter. The dark matter mass turns out to be controlled by the Yukawa couplings of the heavy Higgs triplets, and it can be naturally at the weak scale for a mild hierarchy of the Yukawa couplings.
Minimal dark matter in type III seesaw
Eung Jin Chun
Physics , 2009, DOI: 10.1088/1126-6708/2009/12/055
Abstract: We explore the possibility of a new dark matter candidate in the supersymmetric type III seesaw mechanism where a neutral scalar component of the Y=0 triplet can be the lightest supersymmetric particle. Its thermal abundance can be in the right range if non-standard cosmology such as kination domination is assumed. The enhanced cross-section of the dark matter annihilation to W+W- can leave detectable astrophysical and cosmological signals whose current observational data puts a lower bound on the dark matter mass. The model predicts the existence of a charged scalar almost degenerate with the dark matter scalar and its lifetime lies between 5.5 cm and 6.3 m. It provides a novel opportunity of the dark mater mass measurement by identifying slowly-moving and highly-ionizing tracks in the LHC experiments. If the ordinary lightest supersymmetric particle is the usual Bino, its decay leads to clean signatures of same-sign di-lepton and di-charged-scalar associated with observable displaced vertices which are essentially background-free and can be fully reconstructed.
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