• Bulletin of the Korean Chemical Society
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• v.24 no.6
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• pp.864-880
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• 2003

A unified picture for magnetism, superconductivity, quantum optics and other properties of molecule-based materials has been presented on the basis of effective model Hamiltonians, where necessary parameter values have been determined by the first principle calculations of cluster models and/or band models. These properties of the matetials are qualitatively discussed on the basis of the spin and pseudo-spin Hamiltonian models, where several quantum operators are expressed by spin variables under the two level approximation. As an example, ab initio broken-symmetry DFT calculations are performed for cyclic magnetic ring constructed of 34 hydrogen atoms in order to obtain effective exchange integrals in the spin Hamiltonian model. The natural orbital analysis of the DFT solution was performed to obtain symmetry-adapted molecular orbitals and their occupation numbers. Several chemical indices such as information entropy and unpaired electron density were calculated on the basis of the occupation numbers to elucidate the spin and pair correlations, and bonding characteristic (kinetic correlation) of this mesoscopic magnetic ring. Both classical and quantum effects for spin alignments and singlet spin-pair formations are discussed on the basis of the true spin Hamiltonian model in detail. Quantum effects are also discussed in the case of superconductivity, atom optics and quantum optics based on the pseudo spin Hamiltonian models. The coherent and squeezed states of spins, atoms and quantum field are discussed to obtain a unified picture for correlation, coherence and decoherence in future materials. Implications of theoretical results are examined in relation to recent experiments on molecule-based materials and molecular design of future molecular soft materials in the intersection area between molecular and biomolecular materials.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.360-360
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• 2012

Graphene shows diverse novel physical properties arising from its peculiar electronic states, so called Dirac electrons. Especially, effect of magnetic field is very unique, exhibiting exotic Landau level (LL) splitting. LLs are substantially modified by spins of Dirac electrons and pseudo-spins. The degeneracy of LLs is lifted to show splitting by electron-electron interaction and by the Zeeman effect. We investigated the magneto-optical absorption of graphene subjected to ultra-high magnetic field. Samples were prepared by the CVD method deposited on GaAs and Quart substrate. We have confirmed existence of graphene on each substrate by the micro-Raman spectroscopy. Next, we conducted magneto-absorption measurements in magnetic field up to 120 T by the single-turn coil (STC) method. We could observe absorption peak at 65 T and 100 T, respectively, probably arising from the LL inter-band transitions.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.5
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• pp.863-869
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• 2008

In this paper, a system with sensor network security mechanism which can be applied to home network structure is designed and it is implemented on a virtual network of a home network middleware. The basic structure of home networking middleware supports one-to-one (unicast) or broadcast communication mode between the lookup server and service nodes on the network. Confidentiality and authentication are key security factors of the one-to-one communication and user authentication is crucial for broadcasting mode. One of the sensor network's security techniques SPINS consists of SNEP and ${\mu}TESLA$. The SNEP ensures confidentiality and authentication, and ${\mu}TESLA$ provides broadcast authentication. We propose a SPIN based home network middleware and it is implemented by using the CBC-MAC for MAC generation, the counter mode (CTR) for message freshness, the pseudo random function (PRF) and RC5 as encryption algorithm. The implementation result shows that an attacker cannot decrypt the message though he gets the secure key because of CTR mode. In addition, we confirmed that a received message of the server is authenticated using MAC.