• Journal of Korean Ophthalmic Optics Society
• /
• v.3 no.1
• /
• pp.15-19
• /
• 1998

The purpose of this study, when one prepared lead zirconate thin films by sol-gel method, was to find the preferred direction of crystal growth and dielectric characteristics for ratio of Pb and Zr. We used the Pt/Ti/$SiO_2$/Si substrate, and annealing condition was $800^{\circ}C$ for lminute. When Pb was deficient, preferred direction was <221>. And when it was stoichiometric ratio, they were grown <200> and <221> direction. But they have antiferroelectric properties, they don't appear distinct domain switching.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
• /
• v.6 no.1
• /
• pp.48-65
• /
• 1995

This paper deals with the analysis of the unintentional radiation from the TDX-1B subscriber Board. According to the demand of digital systems and developement of high speed switching devices, electro- magnetic noise intensity and it's bandwidth occupancy in spectrum are increasing and so there is a serious possibility causing the various EMI phenomena. More accurate radiation model was established by using the Finite Difference Time Domain (FDTD) analysis, and the EMI probabilistic analysis of the digital switching system was performed. For validating the proposed model and its calculated results, on-promises test was performed and compared with the calculated results. These results may be applicable to be used for EMI model in large digital system, and prediction of EMI effect from a large digital system, and the EMI control design when designing digital system to meet inter- national EMI regulation.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.9 no.8
• /
• pp.1774-1779
• /
• 2005

This paper propose the design method of the constructing the digital logic systems over galois fields using by the galois field decision diagram(GFDD) that is based on the graph theory. The proposed design method is as following. First of all, we discuss the mathematical properties of the galois fields and the basic properties of the graph theory. After we discuss the operational domain and the functional domain, we obtain the transformation matrixes, $\psi$GF(P)(1) and $\xi$GF(P)(1), in the case of one variable, that easily manipulate the relationship between two domains. And we extend above transformation matrixes to n-variable case, we obtain $\psi$GF(P)(1) and $\xi$GF(P)(1). We discuss the Reed-Muller expansion in order to obtain the digital switching functions of the P-valued single variable. And for the purpose of the extend above Reed-Muller expansion to more two variables, we describe the Kronecker product arithmetic operation.

• Journal of Power Electronics
• /
• v.18 no.3
• /
• pp.892-901
• /
• 2018

SiC MOSFETs have been used to improve system efficiency in high frequency converters due to their extremely high switching speed. However, this can result in undesirable parasitic oscillations in practical systems. In this paper, models of the key components are introduced first. Then, theoretical formulas are derived to calculate the switching oscillation frequencies after full turn-on and turn-off in clamped inductive circuits. Analysis indicates that the turn-on oscillation frequency depends on the power loop parasitic inductance and parasitic capacitances of the freewheeling diode and load inductor. On the other hand, the turn-off oscillation frequency is found to be determined by the output parasitic capacitance of the SiC MOSFET and power loop parasitic inductance. Moreover, the shifting regularity of the turn-off maximum peak voltage with a varying switching speed is investigated on the basis of time domain simulation. The distortion of the turn-on current is theoretically analyzed. Finally, experimental results verifying the above calculations and analyses are presented.

• Journal of Magnetics
• /
• v.6 no.4
• /
• pp.132-141
• /
• 2001

The switching characteristics and the magnetization-flop behavior in magnetic tunnel junctions exchange biased by synthetic antiferromagnets (SyAFs) are investigated by using a computer simulations based on a single-domain multilayer model. The bias field acting on the free layer is found to be sensitive to the thickness of neighboring layers, and the thickness dependence of the bias field is greater at smaller cell dimensions due to larger magnetostatic interactions. The resistance to magnetization flop increases with decreasing cell size due to increased shape anisotropy. When the cell dimensions are small and the synthetic antiferromagnet is weakly, or not pinned, the magnetization directions of the two layers sandwiching the insulating layer are aligned antiparallel due to a strong magnetostatic interaction, resulting in an abnormal magneto resistance (MR) change from the high-MR state to zero, irrespective of the direction of the free-layer switching. The threshold field for magnetization-flop is found to increase linearly with increasing antiferromagnetic exchange coupling in the synthetic antiferromagnet. Irrespective of the magnetic parameters and cell sizes, magnetization flop does not exist near zero applied field, indicating that magnetization flop is driven by the Zeeman energy.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2011.08a
• /
• pp.186-186
• /
• 2011

[100] 방향으로 4$^{\circ}$ 기울어진 Si(001)-2${\times}$1(vicinal surface)을 초고진공하(UHV)에서 청결하게 하고 열처리하면 rebonded-atom을 가진 DB double step과 이 step에 나란한 아홉 개의 dimer를 가진 평균 폭이 4.0 nm인 single-domain의 (001)-2${\times}$1 테라스의 면으로 재구조된다 [그림 a]. 본 연구에서는 이 표면 위에 Sb을 상온에서 증착하여 덮고 후열처리하면(2 ML, 500$^{\circ}C$ 10 분), Sb-dimer가 Si 표면을 한 층 덮고 (001) 테라스의 Sb-dimer 방향이 DA double-step과 수직을 이루는 1${\times}$2 구조를 이룬다는 사실을 STM으로 확인하였다 [그림 b]. 이러한 Sb-passivation의 효과는 표면 Si-dimer의 부분적으로 채워진 dangling-bond를 Sb-dimer의 완전히 채워진 고립쌍(lone-pair)으로 바꿈으로써 표면 자유 에너지를 줄이고, 나아가 계면 Si 층은 bulk에 유사하게 되는 데에 있다. 이 passivation 된 표면은 Ge/Si 등의 heteroepitaxy에 사용할 수 있고, 특히 single-domain을 유지하며 step 방향에 대해 평행인 dimer-row로 이루어져 있어서 원자나 전자의 이동에 비등방적 효과를 증가시킬 것이 예측된다.

• Journal of Magnetics
• /
• v.13 no.4
• /
• pp.120-123
• /
• 2008

Magnetization ringing following domain wall collision on a ferromagnetic nanowire has been investigated by micromagnetic simulation. Suppressed magnetization ringing is observed with the introduction of a small ribbon to the nanowire. Magnetization ringing has been analyzed in a frequency space by a fast Fourier transform. With the introduction of a small ribbon and/or taping of the wire, the amplitude of ringing is reduced with a shifted frequency peak.

• Journal of Magnetics
• /
• v.10 no.2
• /
• pp.58-62
• /
• 2005

Periodic magnetic nanodot arrays were successfully produced on glass substrates by interference laser lithography and electron beam lithography methods. Magnetic force microscopy (MFM) observation was carried out on fabricated nanodot arrays. MFM tip induced magnetization effects were clearly observed in ferromagnetic elliptical nanodots varying in material and aspect ratio. Fe-Cr dots with a high aspect ratio show reversible switching of the single domain magnetization state. At the same time, Co nanomagnets with a low aspect ratio exhibit tip induced transitions between the single domain and the vortex state of magnetization. The simple nanolithography is potentially an efficient method for fabrication of patterned magnetic arrays.

• Journal of Institute of Control, Robotics and Systems
• /
• v.14 no.2
• /
• pp.111-117
• /
• 2008

This paper presents a new continuation-based quasi-steady-state(CQSS) time-domain simulation algorithm incorporating a multiplicative aggregated load model for power systems. The authors' previous paper introduced a CQSS algorithm, which has the robust convergent characteristic near the singularity point due to the application of a continuation method. The previous CQSS algorithm implemented the load restoration in power systems using the exponent-based load recovery model that is derived from the additive dynamic load model. However, the reformulated exponent-based model causes the inappropriate variation of short-term load characteristics when switching actions occur, during time-domain simulation. This paper depicts how to incorporate a multiplicative load restoration model, which does not have the problem of deforming short-term load characteristics, into the time simulation algorithm, and shows an illustrative example with a 39-bus test system.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.21 no.3
• /
• pp.57-66
• /
• 2011

The current trend of the handover authentication delay time is gradually increased according to the interworking between 3G cellular network and WLANs. Therefore, authentication mechanism minimized in delay is required to perform the seamless handover and support the inter-subnet and inter-domain handover. In this paper, we propose a novel pre-authentication scheme based on the fast channel switching which directly performs the authentication with the next access point in advance. In addition, the proposed scheme is efficient in the inter-domain handover and can be easily implemented in current WLANs since it just modifies the client side of user. To analysis and evaluate our scheme, we compare the packet loss ratio and the delay time with the two standard 802.11 authentication schemes. The analytical results show that our scheme is approximate 10 times more effective than the standard schemes in packet loss and the delay time is minimized down to 0.16 msec.