• The Transactions of the Korean Institute of Power Electronics
• /
• v.3 no.3
• /
• pp.214-221
• /
• 1998

A new control approach using neural network for the robust position control of a BRUSHLESS direct drive(BLDD) motor is presented. The linear quadratic controller plus feedforward neural network is employed to obtain the robust BLDD motor system approximately linearized using field-orientation method for an AC servo. The neural network is trained in on-line phases and this neural network is composed by a feedforward recall and error back-propagation training. Since the total number of nodes are only eight, this system will be easily realized by the general microprocessor. During the normal operation, the input-output response is sampled and the weighting value is trained by error back-propagation at each sample period to accommodate the possible variations in the parameters or load torque. And the state space analysis is performed to obtain the state feedback gains systematically. In addition, the robustness is also obtained without affecting overall system response.

• Journal of KIISE:Software and Applications
• /
• v.35 no.1
• /
• pp.12-21
• /
• 2008

As the usage of computer systems is increasing in our lives, the reliability and safely of these systems need to be thoroughly checked through the verification techniques. As a basic formalism for several modeling methods, the finite state machine (FSM) is widely used in specification and verification of system models. And there is a technique for ing internal events of FSM in order to effectively analyze the system. However, this technique does not handle the state explosion problem since it can be applied after completely generating all the state space of the system. In this research, we provide a new approach for efficiently representing concurrent properties of FSM, the slice model and provide an efficient transition reduction method based on the slice model. Our approach is effective in time and space perspective since it is peformed by partially generating the needed system states while the existing abstraction technique can be applied to all the system states.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2003.11a
• /
• pp.366-367
• /
• 2003

암모니아 가스는 무색의 기체이지만 자극성이 크면서 부식성이 있고 수용액이 알칼리성인 대표적인 악취물질이다. 보통의 경우는 굴뚝 등에서 배출가스의 형태로 대량 방출되기도 하지만 자연상태에서도 여러 가지 생물학적 또는 화학적 반응 등을 통하여 생성되므로, 일상적인 생활 공간에서도 쉽게 검출될 수 있는 물질이다. 대기 중 암모니아의 농도는 기체상 시료를 직접 분석하는 가스 크로마토그래피와 시료를 액체상으로 변환시킨 후 암모늄 양이온의 농도를 분광광도법이나 중화적정법으로 측정한다. (중략)

• Journal of the KSME
• /
• v.33 no.12
• /
• pp.1076-1085
• /
• 1993

레이저광이 가지는 지향성, 단색성, 공간적 집속성 등의 성질을 이용하는 각종 측정장치는 광섬 유의 발달과 새로운 신호처리계의 개발로 그 적용 범위가 점점 확대되고 있다. 레이저 도플러 신호의 위상차를 이용하여 운동상태의 입자의 크기와 속도를 동시에 측정할 수 있는 측정장치가 80년대에 실용화되어 캐비테이션, 분무노즐, 기름버너, 엔진연소 등 많은 분야에서 다양하게 사 용되고 있다. 이 측정방법은 Durst와 Zare에 의해 도플러 신호의 위상과 입자의 크기는 선형적인 함수 관계가 있음이 밝혀진 이래, Bachalo, Buchhave, Knuhfsen과 Olldag 등에 의해 급속히 발 전되었다. 현재 국내에도 덴마크의 단텍사, 미국의 에어로메트릭스사 등에서 개발한 장비가 3-4 기관에서 사용되고 있다. 이 글에서는 위상도플러법에 의한 입자의 크기측정에 관한 기초 이론을 참고문헌을 인용하여 설명하고, 단텍사에서 개발한 위상도플러 측정장치인 입자운동 해석장치 (PDA)를 사용하여 본 연구실에서 실험한 버너용 압력분사식 노즐에서 분사된 액적들의 국소부분 거동에 대해 소개하기로 한다.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.32 no.9
• /
• pp.297-304
• /
• 1983

This paper deals with the electric fileds calculation by combination of finite element method and charge simulation method. Since this method has the advantage of both F.E.M and C.S.M.the application of this method is more useful for the caleulation of non-enclosed fields, multi-dielectric fields, space charge fields and so on. On the basis of this method, computer programs for the calculation of two-demensional and axisymmetric fields were developed. This paper shows that the calculation results are accurately abtained through several examples.

• The Journal of Engineering Geology
• /
• v.15 no.3
• /
• pp.245-255
• /
• 2005

Three dimensional Monte-Carlo simulations of non-ergodic transport of a non-reactive solute plume by steady-state groundwater flow under a uniform mean velocity in isotropic heterogeneous aquifers were conducted. The log-normally distributed hydraulic conductivity, K(x), is modeled as a random field. Significant efforts are made to reduce the simulation uncertainties. Ensemble averages of the second spatial moments of the plume, $$lt;S_{ij}'(t',l')$gt;$ and plume centroid variances, $$lt;R_{ij}'(t',l')$gt;$ were simulated with 3200 Monte Carlo runs for three variances of log K, $\omega^2_y1.0,,2.5,$ and 5.0, and three dimensionless lengths of line plume sources ( l=,5 and 10) normal to the mean velocity. The simulated second spatial moment and the plume centroid variance in longitudinal direction fit well to the first order theoretical results while the simulated transverse moments are not fit well with the first order results. The first order theoretical results definitely underestimated the simulated transverse second spatial moments for the aquifers of large u: and small initial plume sources. The ergodic condition for the second spatial moments is far from reaching, and the first order theoretical results of the transverse second spatial moment of the ergodic plume slightly underestimated the simulated moments.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
• /
• v.19 no.4
• /
• pp.24-31
• /
• 2005

A plused laser ablation deposition(PLAD) technique has been used for producing fine particle as well as thin film at relatively low substrate temperatures. However, in order to manufacture and evaluate such materials in detail, motions of plume particles generated by laser ablation have to be understood and interactions between the particles by ablation and gas plasma have to be clarified. Therefore this paper was focused on the understanding of plume motion in laser ablation assisted by hi plasmas at 100[mTorr]. One-dimensional hybrid model consisting of fluid and particle models was developed and three kinds of plume particles which are carbon atom(C), $ion(C^+)$ and electron were considered in the calculation of particle method. It was obtained that ablated $C^+$ was electrically captured in Ar plasmas by strong electric field(E). The difference between motions of the ablated electrons and $C^+$ made E strong and the collisional processes active. The energies of plume particles were investigated on a substrate surface. In addition the plume motion in Ar gas was also calculated and discussed.

• KSBB Journal
• /
• v.11 no.4
• /
• pp.453-461
• /
• 1996

We compared the effects of two different systems of collagen matrix protein application on the survival and the biological functions of cultured primary hepatocytes. The rat liver primary hepatocytes were grown for approximately 40 days in vitro either on single collagen gel or between collagen sandwich gels. The morphological changes were observed for this culture period. While the hepatocytes grown on single gel began to die around at 7 days of culture, the cells grown between collagen gels still maintained their viability and began to die after 15 days. As markers for liver hepatic functions, we determined the biochemical activities of hepatocytes such as the secretions of albumin, fibronectin, fibrinogen, urea, and the reduction of secreted ammonia. We found that the rat hepatocytes cultured between collagen gels maintained fairly good biochemical functions than the hepatocytes cultured on single gel did. Therefore, the application of an extracellular matrix protein, collagen, in sandwich form was confirmed as a better choice for maintaining the functional hepatocytes culture for long term in vitro.

• Journal of The Korean Association For Science Education
• /
• v.27 no.4
• /
• pp.346-353
• /
• 2007

In order to be efficient in teaching, a teacher should understand the current learner's level through diagnostic evaluation. This study has examined the major issues arising from the noble diagnostic assessment tool based on the theory of knowledge space. The knowledge state analysis method is actualizing the theory of knowledge space for practical use. The knowledge state analysis method is very advantageous when a certain group or individual student's knowledge structure is analyzed especially for strong hierarchical subjects such as mathematics, physics, chemistry, etc. Students' knowledge state helps design an efficient teaching plan by referring their hierarchical knowledge structure. The knowledge state analysis method can be enhanced by computer due to fast data processing. In addition, each student's knowledge can be improved effectively through individualistic feedback depending on individualized knowledge structure. In this study, we have developed a diagnostic assessment test for measuring student's learning outcome which is unattainable from the conventional examination. The diagnostic assessment test was administered to middle school students and analyzed by the knowledge state analysis method. The analyzed results show that students' knowledge structure after learning found to be more structured and well-defined than the knowledge structure before the learning.

• Journal of the Korean Geographical Society
• /
• v.43 no.3
• /
• pp.392-411
• /
• 2008

The purpose of this paper is to develop a method for exploring hotspot patterns of house price volatility where there is a high fluctuation in price and homogeneity of direction of price volatility. These patterns are formed when the majority of householders in an area show an adaptive tendency in their decision making. This paper suggests a method that consists of two analytical parts. The first part uses spatial scan statistics to detect spatial clusters of houses with a positive range of price volatility. The second part utilizes local Moran's I to evaluate the homogeneity of direction of price volatility within each cluster. The method is applied to the areas of Gangnam-Gu, Seocho-Gu, and Songpa-Gu in Seoul from August to November of 2003; the Participatory Government of Korea designated these areas and this period as the most speculative. The results of the analysis show that the area around Gaepo-Dong was as a hotspot before the Government's anti-speculative 10.29 policy in 2003; the house prices in the same area stabilized in October, 2003 and the area was identified as a coldspot in December, 2003. This case study shows that the suggested method enables exploration of hotspot of house price volatility at micro spatial scales which had not been detected by visual analysis.