• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2001년도 합동 추계학술대회 논문집 정보 및 제어부문
• /
• pp.42-45
• /
• 2001

In the speed-sensorless induction motor control systems, only a few percents of error in current measurement badly deteriorates the control performance. And early detection and accomodation of the faults of current sensor is very important to enhance the reliability of the induction motor control system. In this paper, we propose two sensor fault detection schemes having desired functions; fault detection, isolation of failed sensor and compensation of fault effect. The two schemes operate in real-time and employ EKFs (Extended Kalman Filter) for residual generation. Simulation results show that the proposed schemes are very useful in maintaining the control performance of the induction motor driven servo systems even in the face of sensor faults.

• 소성∙가공
• /
• 제12권5호
• /
• pp.457-464
• /
• 2003

In the powder compact melting technique, proper precursor fabrication is very important because density distribution after foaming and foamability are determined during precursor fabrication process. The fabrication of the precursor has to be performed very carefully because any residual porosity or other defects will lead to poor results in further processing. In order to evaluate the effect of the compaction parameters on the kinetics of the foaming process, a series of experiments were performed. In this study, aluminium foams with a closed cell structure were fabricated by using both the powder compact method and the induction heating process. A proper induction coil was designed to obtain a uniform temperature distribution over the entire cross sectional area of precursor. To establish the foamable precursor fabrication conditions, effects of process parameters such as the titanium hydride content (0.3∼1.5 wt.%), pressing pressure of the foamable precursor (50∼150kN) on the pore morphology were investigated.

• 한국해양공학회지
• /
• 제23권2호
• /
• pp.74-80
• /
• 2009

Surface hardening treatments, such as using the high-frequency induction hardening method, are widely used to increase the fatigue life and prevent the failure of materials by locally increasing the surface hardness. This method, in particular, brings an improvement in static strength by compressive residual surface stress due to the hardening. In this study, the mechanical properties of high-frequency induction hardened SCM440 steel were investigated. These results were also compared with those for base metal and a Q/T (tempering after quenching) treatment specimen. The test results showed that partially high-frequency induction hardened SCM440 steel specimens were more improved in static strength, surface hardness, fatigue limit, and anti-wear than the base metal and Q/T treatment specimens. In particular, the fatigue limit of the high-frequency induction hardened SCM440 steel increased by more than about 52% compared to that of base metal and by about 25% compared to that of the Q/T specimen.

• 대한조선학회논문집
• /
• 제37권3호
• /
• pp.110-121
• /
• 2000

선상가열의 열원으로는 가스 가열법, 고주파 유도 가열법, 그리고 레이저 가열법 등이 사용될 수 있다. 가스 가열법은 많은 조선소등에서 사용되고 있으나 가열 후 얻어지는 잔류변형을 제어하는데 많은 어려움이 있다. 고주파 유도 가열법은 비교적 정확한 변형량 제어가 가능하다는 장점을 가지고 있어서 새로운 선상가열 열원으로서 활용될 수 있을 것이다. 본 연구에서는 고주파 유도가 열법을 이용한 선상 가열의 변형 특성 및 가열장치의 특성을 파악하기 위한 기본단계로써 고주파 유도가열에 의한 열변형 과정에 대한 해석을 시도하였다. 전자장 해석과 와전류 해석, 와전류에 의하여 판에 발생하는 온도 분포, 그리고 열탄소성 변형 해석을 수행하였다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2009년도 춘계학술대회 논문집 전기설비전문위원
• /
• pp.77-79
• /
• 2009

Nonlinear system fault detection and isolation of this paper is about the failure of unknown function approximation using neural network for fault detection and isolation techniques of induction motors were applied. observer-based fault signal residual value was used. Induction motor using the speed controller of the backstepping controller. Proposed fault detection and isolation to prove the performance of the simulation was applied to and the actual system.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제53권3호
• /
• pp.145-153
• /
• 2004

A nonlinear adaptive speed observer is designed for the sensorless control of induction motors. In order to design the speed observer, the measurements of the stator currents and the estimates of the rotor fluxes are used. The sliding mode cascade observer is designed to estimate the time derivatives of the stator currents. The open-loop observer is designed to estimate the rotor fluxes and its time derivatives using the stator current derivatives. The adaptive observer is also designed to estimate the rotor resistance. Sequentially, the rotor speed is calculated using these estimated values. It is shown that the estimation errors of the corresponding states and the parameters converge to the specified residual set. It is also shown that the speed controller using these estimates is performed well. The simulation examples are represented to investigate the validity of the proposed observers for the sensorless control of induction motors.

• 전기의세계
• /
• 제21권6호
• /
• pp.17-20
• /
• 1972

The magnetic properties of Ba-Ferrite ( $M^{+2}$O.nF $e_{2}$ $O_{3}$ is highly improved under the condition of composition ratio n=4.4 when B $i_{2}$ $O_{3}$ is added to Ferrite, the adding amount and sintering temperature which affect the magnetic properties were investigated and the following results; were obtained; 1. Magnetic properties are varied with B $i_{2}$ $O_{3}$ content and singering temperature, and coercive force and residual induction can be improved with B $i_{2}$ $O_{3}$. 2. The optimal content of B $i_{2}$ $O_{3}$ amount is about 4 mol %, 3. Without the addition of B $i_{2}$ $O_{3}$, the optimal sintering temperature is about 1300.deg. C, but when 4 mol % of B $i_{2}$ $O_{3}$ is added, the optimal sintering temperature falls to the range of 900.deg. C to 1100.deg. C and it also improves magnetic properties. 4. Residual induction increases as the singering temperature is raised to 1100.deg. C. Coercive force also increased as the sintering temperature is raised to 1000.deg. C, but it rapidly decreases when sintering temperature goes beyond 1000.deg. C. 5. Only a negligible change may be noticed in the decrease of Curie temperature by the addition of about 4 mol % of B $i_{2}$ $O_{3}$.

• Clinical and Experimental Pediatrics
• /
• 제53권11호
• /
• pp.957-964
• /
• 2010

Purpose: Our study attempted to determine the prognostic significance of minimal residual disease (MRD) detected by a simplified flow cytometric assay during induction chemotherapy in children with B-cell acute lymphoblastic leukemia (B-ALL). Methods: A total of 98 patients were newly diagnosed with precursor B-ALL from June 2004 to December 2008 at the Asan Medical Center (Seoul, Korea). Of those, 37 were eligible for flow cytometric MRD study analysis on day 14 of their induction treatment. The flow cytometric MRD assay was based on the expression intensity of CD19/CD10/CD34 or aberrant expression of myeloid antigens by bone marrow nucleated cells. Results: Thirty-five patients (94.6%) had CD19-positive leukemic cells that also expressed CD10 and/or CD34, and 18 (48.6%) had leukemic cells with aberrant expression of myeloid antigens. Seven patients with ${\geq}1%$ leukemic cells on day 14 had a significantly lower relapse-free survival (RFS) compared to the 30 patients with lower levels (42.9 % [18.7%] vs. 92.0% [5.4%], $P$=0.004). Stratification into 3 MRD groups (${\geq}1%$, 0.1-1%, and <0.1%) also showed a statistically significant difference in RFS (42.9% [18.7%] vs. 86.9% [8.7%] vs. 100%, $P$=0.013). However, the MRD status had no significant influence on overall survival. Multivariate analysis demonstrated that the MRD level on day 14 was an independent prognostic factor with borderline significance. Conclusion: An MRD assay using simplified flow cytometry during induction chemotherapy may help to identify patients with B-ALL who have an excellent outcome and patients who are at higher risk for relapse.

• Journal of Microbiology and Biotechnology
• /
• 제14권2호
• /
• pp.225-230
• /
• 2004

A plasminogen kringle domain 1 to 3, rKl-3, was expressed in Escherichia coli under the control of T7 promoter. For the cost-effective production of rKl-3, the induction process was analyzed and optimized. Induction characteristics with lactose were analyzed in terms of induction time and inducer concentration in various culture conditions including batch and high-cell-density fed-batch cultures. In the fed-batch culture, the induction around 6 h after initiation of the DO-stat fed-batch culture resulted in the highest expression level of rKI-3 among the induction points examined. The highest demand of oxygen at this point was crucial for the maximum expression level of rKI-3. As the lactose concentration increased, the expression level also increased, though the expression level showed a plateau above a concentration of 14 mM of lactose. Lactose acted less specifically than IPTG since most of it was hydrolyzed to glucose and galactose. However, using lactose, the cell growth and the maximum expression level of rKl-3 increased by 20% and 24%, respectively, compared with those using IPTG in the fed-batch culture. The lactose seemed to be hydrolyzed by intracellular and extracellular $\beta$-galactosidase liberated by cell lysis at the same time. Residual concentration of glucose was maintained to a a limit of detection by high performance liquid chromatography, and galactose was not consumed by the host strain Escherichia coli BL2l(DE3).

• 한국항행학회논문지
• /
• 제14권6호
• /
• pp.831-837
• /
• 2010

광 시간 분할 다중/파장 분할 다중 (OTDM/WDM; optical time division multiplexing/wavelength division multiplexing) 전송 시스템의 구현을 위한 40 Gbps RZ 형식의 최적 조건을 충격 계수 (duty cycle)와 소광비 (ER; extinction ratio)에 따른 성능 분석과 비교를 통해 도출하였다. 광전송 링크에는 광섬유의 색 분산과 비선형에 의한 신호 왜곡을 보상하기 위해 광 위상 공액기 (OPC; optical phase conjugator)와 inline 분산 제어 (DM; dispersion management)가 적용되었다. ER에 따른 시스템 성능 변화의 영향이 적으면서 동시에 OTDM에 의한 160 Gbps 신호로의 다중화에 적합한 충격 계수는 0.25이라는 것을 확인하였다. 또한 DM의 적용에 있어 중계 거리 당 잉여 분산 (RDPS; residual dispersion per span)을 크게 할수록 동일한 전체 잉여 분산 (NRD; net residual dispersion)에 의해 결정되는 RZ 형식의 성능 개선 정도를 증가시킬 수 있는 것을 알 수 있었다.