• 한국대기환경학회지
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• 제16권5호
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• pp.445-451
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• 2000

To estimate dry deposition flux of 12 elements in aerosols, aerosol particles were sampled by a low-pressure impactor(LPI) and a dust jar. The concentrations of 12 elements in aerosol particle and dry deposition were analyzed by a PIXE analysis using as a 2.0 MeV-proton beam. The mean dry deposition velocities of 12 elements were estimated by ranges of 0.74∼2.62 cm/sec. The results showed that the highest value was 3.26 cm/sec for Ca and the lowest value 0.74 cm/sec for Fe. The dry deposition flux for elements was calculated as a function of particle size by 1-step method and 12-step method. In this work, dry deposition velocities were computed with the two existing models; the coarse-particle fraction(4∼30 mm diameter) using the dry deposition velocity model of the Noll and Fang(1998) and the fine-particle fraction (0.05∼4mm diameter) using the Shemel and Hodgson(1980) model. The ratios of the mean calculated/measured fluxes were 3.59 for 1-step method and 0.60 for 12-step method respectively.

• 전기전자학회논문지
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• 제23권1호
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• pp.9-13
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• 2019

본 논문에서는 원가 절감을 위한 개선된 $165^{\circ}$ 12 스텝 제어를 고려한 브러시리스 DC 전동기의 최적화 설계에 대하여 논한다. 개선된 12 스텝 제어는 기존 제어의 도통각 $150^{\circ}$을 확장시켜 전동기의 출력을 향상 시킬 수 있다. 향상된 전동기 출력을 고려한 반응 표면법을 이용한 최적화 설계를 통해서 회전자, 고정자 및 영구자석의 부피를 감소시켜 원가절감이 가능한 설계를 제시한다. 제안된 설계는 기존 전동기의 요구 사양 및 효율 향상을 만족하고 기존 전동기 중량의 약 3.5%를 저감하였다. 유한요소법을 이용한 전자계 해석을 통해 최적화 설계의 타당성을 입증하였다.

• 대한기계학회논문집A
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• 제27권12호
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• pp.2047-2054
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• 2003

In this paper, an approach of automatically finding and modifying the most appropriate orthogonal array (GO) is suggested and applied to a new structural optimization procedure with two steps. GO is motivated by the situation where finding a proper orthogonal array from the tables in the literature is difficult or impossible. Now the Taguchi method is made available for various numbers of variables and levels. In the two-step structural optimization, the Taguchi method equipped with GO and a shape optimization using the finite differencing method is consecutively applied. The existence or non-existence of an element can be taken as a factor level and this feature is utilized finding the best topology from a set of potential topologies suggested from the user's expertise. This greatly enhances applicability and one can expect a better result than the case in which each step is applied independently because these steps are complementary each other.

• 대한기계학회논문집A
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• 제21권12호
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• pp.2055-2067
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• 1997

Values of process parameters in sheet metal forming can be estimated by various one-step inverse methods. One-step inverse methods based on deformation theory, however, cause some amount of error. The amount of error is generally increased as the deformation path becomes more complex. As a remedy, a new three dimensional multi-step inverse method is introduced for optimum design of blank shapes and strain distributions from desired final shapes. The approach extends a one-step inverse method to a multi-step inverse method in order to reduce the amount of error. The algorithm developed is applied to square cup drawing to confirm its validity by demonstrating reasonably accurate numerical results. Rapid calculation with this algorithm enables easy determination of an initial blank of sheet metal forming.

• 제어로봇시스템학회논문지
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• 제16권12호
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• pp.1189-1196
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• 2010

This paper provides an identification method for three-parameter models i.e. first order with dead time models and second order with dead time models. The proposed identification method is based on step response and can be easily implemented using digital microprocessors. The proposed method first identifies the order of the plant i.e. first order or second order from the behavior of the plant with constant input. After the order of the plant is determined, a test step input is applied to the system and the three parameters of the plant are obtained from the corresponding response of the plant. The output of the plant need not to be zero when the test signal is applied. The efficacy of proposed algorithms is verified through simulation and experiment.

• 전력전자학회논문지
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• 제10권5호
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• pp.450-456
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• 2005

본 논문에서는 새로운 이중접속 방식의 60-스텝 인버터를 제안하고 이를 이용한 대용량 STATCOM에 관하여 동작원리 및 제어방식을 기술하기로 한다. 기존의 12-스텝 인버터에 간단한 보조회로를 추가하여 출력전압의 파형을 60-스텝으로 개선하였다 제안한 방식의 인버터는 커패시터의 전압분할이 필요하지 않아 간접제어 방식의 적용이 용이하며 $10Mvar\~30Mvar$급 범위의 STATCOM에 적용하면 경제적이다. 2KVA급 시작품의 실험결과로부터 제안한 방식의 타당성을 입증하였다.

• 한국염색가공학회지
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• 제11권5호
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• pp.7-12
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• 1999

The objective of this study is to apply water repellent and flame retardant finishes simultaneously to the fabric used for automobile. Both two step and one step methods were tried to apply the finishing agent to the fabric. In the two step method, water repellent agent was treated first, and flame retardant agent was applied next. The reverse finishing process was also attempted. In the one step method, flame retardant agent and water repellent agent treated to the fabric in one bath. The results of two step method revealed that the finishing effect was better when the water repellent agent was treated first than when flame retardant agent was treated first. In one step method, fluoro water repellent agent was superior to silicon water repellent agent.

• 전력전자학회논문지
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• 제11권3호
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• pp.209-215
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• 2006

본 논문에서는 전압원 인버터의 출력전압 파형을 개선하여 PWM방식을 사용할 수 없는 중 대용량급 모터드라이버 및 UPS, STATCOM, SVC등에 적용하기 위한 새로운 3상 전압원 24-스텝 인버터를 제안한다 보조회로로서 사용한 컨버터로 리플전압을 발생시키고 이를 기존의 12-스텝 인버터에 주입하는데 한대의 링크를 사용하면 12-스텝 동작이 24-스텝으로 전환되며 보조 변압기의 1차 권선을 2N(N=1,2,3...)으로 늘리면 12M-스텝(M=2,3,4..)으로 전환된다. 본 방식의 타당성을 실험 및 시뮬레이션을 통하여 입증하였다.

• 대한전기학회논문지
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• 제35권12호
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• pp.567-572
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• 1986

In this paper, a new type of step motor with two degree of mechanical freedom, which is named rotary-Linear Step Motor(RLSM), is presented. Its rotor axis can perform linear and rotary motions either separately or simultaneously. This paper discribes the design of RLSM using finite element method in which the magnetic saturation effect of the iron core is taken into account. The design parameters such as torques, forces and inductances are obtained from the computed magnetic vector potentials. A new type of Rotary-Linear Step Motor was constructed. The calculated parameters agree well with measurements.

• 소성∙가공
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• 제12권5호
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• pp.449-456
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• 2003

Multi-step induction heating process was applied to the powder compact melting technique as a new heating process to achieve pinpoint accuracy, faster cycle time, repeatability, non-contact and energy-efficient heat in a minimal amount of time. The objective of this study is the establishment of the input data diagram of multi step induction heating process for automation of the fabrication process of 6061 Al foams with desired density. At first, proper induction coil was designed to obtain a uniform temperature distribution over the entire cross sectional area of specimen. By using this coil, foaming experiments were performed to investigate the multi-step induction heating conditions such as capacity, temperature and time conditions of each heating and holding step. On the basis of the obtained multi-step induction heating conditions, relationship between final heating temperature and fraction of porosity was investigated.