• ETRI Journal
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• v.32 no.6
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• pp.932-939
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• 2010

In this paper, a fast migration method is proposed. Our method executes local relocation on a model placement where an additional module is added to it for modification with a minimum number of displacements. This method is based on mean-field annealing (MFA), which produces a solution as reliable as a previously used method called simulated annealing. The proposed method requires substantially less time and hardware, and it is less sensitive to the initial and final temperatures. In addition, the solution runtime is mostly independent of the size and complexity of the input model placement. Our proposed MFA algorithm is optimized by enabling module rotation inside an energy function called permissible distances preservation energy. This, in turn, allows more options in moving the engaged modules. Finally, a three-phase cooling process governs the convergence of problem variables called neurons or spins.

• Bulletin of the Korean Chemical Society
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• v.33 no.3
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• pp.980-986
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• 2012

In this paper we develop a minimalist model of single molecule spectroscopy in a dynamic environment. Our model is based upon a lattice system consisting of a probe molecule embedded in an Ising-model like environment. We assume that the probe molecule interacts with the Ising spins via a dipole-dipole potential, and calculate free energy curves and lineshapes of the system. To investigate fluctuation behavior of the system we exploit the metadynamics sampling method. In particular, using the method, we calculate the free energy curve of magnetization of the lattice and that of the transition energy of the probe molecule. Furthermore, we compare efficiencies of three different sampling methods used; unbiased, umbrella, and metadynamics sampling methods. Finally, we explore the lineshape behavior of the probe molecule as the system undergoes a phase transition from a sub-critical and to a super-critical temperature. We show that the transition energy of a probe molecule is broadly distributed due to the heterogeneous, local environments.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.343-346
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• 2005

In this study, a basic concept of wavelet encoding and its advantages over Fourier based phase encoding application. Wavelet encoding has been proposed as an alternative way to Fourier based phase encoding in magnetic resonance imaging. In wavelet encoding, the RF pulse is designed to generate wavelet-shaped excitation profile of spins. From the resulting echo signals, the wavelet transform coefficients of spin distribution are acquired and an original spin density is reconstructed from wavelet expansion. Wavelet encoding has several advantages over phase encoding. By minimizing redundancy of the data acquisition in a dynamic series of images, we can avoid some encoding steps without serious loss of quality in reconstructed image. This strategy may be regarded as data compression during imaging. Although there are some limitations in wavelet encoding, it is a promising scheme in a dynamic imaging.

• Proceedings of the IEEK Conference
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• 2005.11a
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• pp.1079-1082
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• 2005

In this paper, a secure system is studied and designed for omenetworking middleware based on sensor network security algorithm. Many sensor networks have mission-critical tasks, so it is clear that security needs to be taken into account at design procedure. First, We study homenetworking middleware model in Jini. And we design a security system is applied by SPINS algorithm for moddleware model. Then we firgure out proper secrecy, authentication, broadcast authentication mechanisms in this model.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.05a
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• pp.1007-1010
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• 2006

무선 센서네트워크 환경에서 대칭형 암호화 알고리즘을 적용하는 경우에 제한된 자원과 키 길이로 인하여 다양한 보안 공격에 취약하다. 이러한 문제해결을 위해 온라인상에서 중앙 키 관리 센터를 통해 정기적으로 사용 중인 키를 갱신하는 메커니즘이 필요하다. 여기서 제안된 프로토콜은 정기적인 키 갱신 및 키 정보 인증을 실시하며, 송신자는 키 정보를 암호화하지 않고 공개된 하나의 랜덤 비트 패턴으로 방송한다. 또한 간단하고 빠른 비트위주 XOR 연산을 사용한다. 제안된 키 관리 프로토콜이 네트워크의 성능 측면에서 다른 프로토콜보다 우수함을 보이기 위해 기존의 대칭키 암호화 프로토콜, 마스터 키 기반 SPINS 프로토콜과 비교분석한다.

• Investigative Magnetic Resonance Imaging
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• v.3 no.1
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• pp.13-19
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• 1999

MRI imaging provides many benefits such as noninvasive, 3-dimensional imaging capabilities. But it has relatively serious drawback that is the long data collection time, compared with other imaging modality. Many studies have been performed for fast MR imaging. But EPI and SEPI (4-6) are required to expensive hardware. In this paper, we introduce to Burst imaging technique. It can reduce imaging time by use of a mulitple RF excitation technique. Further it is easily implemented to the normal MRI system. But a pixel profile in the conventional burst sequence is so poor that excited area by burst sequence is a small portion of a pixel. This causes poor signal to noise ratio in burst image. therefore frequency sweeping of RF pulse for burst imaging sequence is proposed to improve pixel profile. A burst pulse train is shaped by liner or nonlinear frequency sweeping function so that all the spins within a pixel are excited, thereby improving the signal to noise ratio. It also shows that the pixel profiles are dependent on how frequency sweep is made. Computer simulations with Bloch equation and experimental results obtained using a 1.0 T NMR imaging system are presented.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.1466-1469
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• 2004

Micro spherical lens mold processing method based on mechanical one completes a spherical shape by setting a diamond tool of hundreds $\mu$m radius on spins with high speed and then using Z-axis vertical feeding motion like the fabrication of micro drilling. In this method, we can see unprocessed parts shaped like cylinder and cone and check increasing chatter marks and burrs by setting errors of the central axis of rotation on the edge of the tool. That is why this method doesn't suit for the optical lens mold. In this paper presents unprocessed parts are disappeared and chatter marks and burrs are decreased from centre of the lens after using Run-out measuring and setting system on run-out occurred from setting tool. Also the fabrication characteristics of 6：4 Brass, A1601, PMMA are compared and analyzed, establishing the optimum machining condition on each material.

• Journal of the Korean Magnetic Resonance Society
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• v.12 no.2
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• pp.81-88
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• 2008

Solid HETCOR (Hetero-Correlation) requires homo-dipolar decoupling between proton spins during the evolution and the mixing period in 2D-NMR. There are two different ways of achieving it with pulse sequences. One is based on the multiple pulse (MP) sequence where thousands of intense radio frequency (rf) pulses are used to remove the homo-dipolar interaction between protons. The other is utilizing the so-called Lee-Goldburg (LG) off-resonance scheme where a continuous rf-irradiation is used. In this report, the advantage of one technique to the other, is analyzed. LG version is evaluated better in S/N and easier in setup procedure with the same experimental time.

• Journal of the Korean Magnetic Resonance Society
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• v.12 no.2
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• pp.89-95
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• 2008

Function of protein is frequently related with tautomeric states of histidine sidechains. Thus, several NMR experiments were developed to determine the tautomeric states of histidines. However, poor sensitivity of these experiments caused by long duration of magnetization transfer periods is unavoidable. Here, we alleviate the sensitivity of HCN experiment for determining the tautomeric states of histidine residues using TROSY principle to suppress transverse relaxation of $^{13}C$ spins during long polarization transfer delays involving $^{13}C-^{15}N$ scalar couplings. In addition, this experiment was used to assign the sidechain resonances of histidines. These assignments can be used to follow the pH-titration of histidine sidechains.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.19-19
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• 2003

The injection of spins into nonmagnetic semiconductors has recently attracted great interest due to the potential to create new classes of spin-dependent electronic devices. A recent strategy to achieve control over the spin degree of freedom is based on dilute ferromagnetic semiconductors. Ferromagnetism has been reported in various semiconductor groups including II-Ⅵ, III-V, IV and II-IV,-V$_2$, which will be reviewed. On the other hand, to date the low solubility of magnetic ions in non-magnetic semiconductor hosts and/or low Curie temperature have limited the opportunities. Therefore the search for other promising ferromagnetic semiconducting materials, with high magnetic moments and high Curie temperatures (Tc), is of the utmost importance. In this talk, we also introduce new pure ferromagnetic semiconductors, MnGeP$_2$ and MnGeAs$_2$, exhibiting ferromagnetism and a magnetic moment per Mn at 5K larger than 2.40 ${\mu}$B. The calculated electronic structures using the FLAPW method show an indirect energy gap of 0.24 and 0.06 eV, respectively. We have observed spin injection in MnGeP$_2$ and MnGeAs$_2$ magnetic tunnel junctions through semiconducting barriers.