• 한국기계가공학회지
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• 제11권4호
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• pp.111-117
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• 2012

Dust collecting performance of axial-vane type cyclone for oil mist was analyzed in this study. For predicting cut diameter size of cyclone, the number and angle of vane ($tan{{\beta}_2}^{\prime}$) was simulated by CFD. As the result, $tan{{\beta}_2}^{\prime}$ was decreased as the number of vane was increased and the angle of inclination(${{\beta}_2}^{\prime}$) decreased, and it cause strong swirl flow. Therefore, it could be confirmed that as the number of vane was increased and the angle of inclination was decreased, cut diameter size was decreased. Also, by verifying the results of CFD through experiment, the cut diameter size could be $2{\mu}m$ at $4m^3/min$ of flow rate.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2002년도 추계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.240-242
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• 2002

Recently, most machineries have been small size and mobile type. And human body insertion type endoscope and micro robot technology has been developed. Then the motors used in this field are developed in micro size such as about 2mm in diameter. The structure of this motor is similar to a general brushless DC(BLDC) motor but because of small size there is no position sensor such as hall sensor. In this paper, we propose synchronous driving method for micro BLDC motor without position sensor. We design and manufacture this driver and perform experiment to show the effectiveness of the proposed method.

• 한국재료학회지
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• 제16권1호
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• pp.68-74
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• 2006

2024 Al alloys were severely deformed by equal channel angular pressing(ECAP) to obtain an ultrafine grain structure. The more deformation amount increased, the more grain size decreased. Most of the grain structure were changed from elongated to equiaxed shape with increasing pass number. The morphology of S' phases was also changed from rod-type to spherical type. The grain size of 6 passed specimen was 100 to 200 nm, and the size of S' phases was about 10 nm in the microstructure. XRD measurements have revealed that the texture formed by plastic deformation disappeared in the 6 passed specimen. SP test results described that the start of crack propagation occurred at the transition zone between plastic bending and membrane stretching because of small elongation. The maximum strength of ECA pressed specimen increased 1.9 GPa to 2.9 GPa with increasing pass number.

• 지역연구
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• 제10권1호
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• pp.53-70
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• 1994

The relationships between the Capital gains of housings by tenure, type and size have been analyzed. Major findings are (i) capital gain rate of 'chonsei' housing is larger than that of the owner occupied housing (ii) the small 'chosei' apartment has the highest capital gain rate and the lowest instability index (iii) the smaller the size of housings, the higher the capital gain rate and the smaller the instability index. Even though there is the 'structural change' in the capital gain rates of owner occupied and 'chonsei' housings, they are cointegrated. The capital gain of owner occupied housing is mainly affected by the real estate policies. But, The capital gain of 'chonsei' housing is mainly affected by the business cycle and the aggregate demand management policies.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 하계학술대회 논문집 A
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• pp.400-402
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• 1999

We have developed a new type Automatic Vending Machine(AVM) of a small size with simplification of coin mechanisms. The AVM adopts a new type transportation system named thin film-transportation system. Thin films have advantages of safe guide and transportation of various goods which made from various materials and shapes. The AVM has advantages of low price and simple mechanisms. The compact size($300{\times}330{\times}630$, mm)is realized by the use of simple coin mechanisms and thin-transportation system.

• 한국의류학회지
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• 제19권4호
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• pp.628-636
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• 1995

The purpose of this study was to investigate the general distribution trend of drapery according to the material of flare skirt and the body size. 100% polyester and 100% rayon fabrics were chosen to compare the effect on the material type. The results from this study were as follows. (1) Both materials generally had similar trend of drapery (2) The difference of material influenced the shape and the amount of drapery. The amount of drapery in polyester was more than the one in rayon. (3) Rody size didn't significantly influence the shape of grapery. So it is concluded that material type is more important variable than the body size for the drapery.

• 기술혁신연구
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• 제13권3호
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• pp.77-100
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• 2005

This paper analyzes the determinants of firm's innovative activity, using Korean Innovation Survey (KIS) dataset. Especially, we focused on the role of external networks by partners(other firms or research institutions) in performing innovative activities. The product innovation, product improvement, and process innovation are used as proxies for innovative activity. The explanatory variables such as market concentration ratio, lagged profitability, foreign ownership, export ratio, firm's age, formal R&D activity, and industrial R&D intensity are also considered. With data from 1,124 firms for the two years (2000-2001), we estimated the logistic regression model. The finding is that the determinants of firm's innovative activities differ by type of innovations. We also found that the innovative behavior of SMEs differs from that of large firms. The result confirms that external networks have a strong positive effect on innovative activity. However, the network effects by partners vary across both firm size and type of innovations.

• Bulletin of the Korean Chemical Society
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• 제20권2호
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• pp.203-210
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• 1999

Structural characteristics of isotactic p-alkylphenol acetaldehyde novolak resins with methyl, t-butyl, and t-octyl as the p-substituent and p-t-butylphenol aldehyde novolak resins with methylene, ethylidene, and propylidene as the linkage were calculated using molecular mechanics and molecular dynamics. The five p-alkylphenol aldehyde resins were found to have common structural characteristics that hydroxyl groups of the p-alkylphenols cluster in the center of the molecule by intramolecular hydrogen bonds of hydroxyl groups of the adjacent p-alkylphenols and the alkyl groups are extended out. Distances between oxygen atoms and between p-carbon atoms of the adjacent p-alkylphenols become longer as the size of the p-substituent increases from methyl to toctyl. Bond angles of the linkage built between the adjacent p-alkylphenols become wider by increasing the p-substituent size and by decreasing the linkage size.

• 대한수학회보
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• 제60권4호
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• pp.873-893
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• 2023

In 2017, Nikiforov proposed the A_𝛼-matrix of a graph G. This novel matrix is defined as A_𝛼(G) = 𝛼D(G) + (1 - 𝛼)A(G), 𝛼 ∈ [0, 1], where D(G) and A(G) are the degree diagonal matrix and adjacency matrix of G, respectively. Recently, Zhai, Xue and Liu [39] considered the Brualdi-Hoffman-type problem for Q-spectra of graphs with given matching number. As a continuance of it, in this contribution we consider the Brualdi-Hoffman-type problem for A_𝛼-spectra of graphs with given matching number. We identify the graphs with given size and matching number having the largest A_𝛼-spectral radius for ${\alpha}{\in}[{\frac{1}{2}},1)$.

• 비파괴검사학회지
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• 제33권6호
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• pp.505-510
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• 2013

An encircling send-receive type pulsed eddy current (PEC) probe is designed for use in aluminum tube inspection. When bare receive coils located away from the exciter were used, the peak time of the signal did not change although the distance from the exciter increased. This is because the magnetic flux from the exciter coil directly affects the receive coil signal. Therefore, in this work, both the exciter and the sensor coils were shielded in order to reduce the influence of direct flux from the exciter coil. Numerical simulation with the designed shielded encircling PEC probe showed the corresponding increase of the peak time as the sensor distance increased. Ferrite and carbon steel shields were compared and results of the ferrite shielding showed a slightly stronger peak value and a quicker peak time than those of the carbon steel shielding. Simulation results showed that the peak value increased as the defect size (such as depth and length) increased regardless of the sensor location. To decide a proper sensor location, the sensitivity of the peak value to defect size variation was investigated and found that the normalized peak value was more sensitive to defect size variation when the sensor was located closer to the exciter.