• 산업공학
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• 제10권1호
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• pp.47-55
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• 1997

This paper deals with an assembly process of the TFT glasses and the color filters in LCD manufacturing. Two specific problems are presented and solved. One is a matching problem to find the best matches between a set of TFT glasses and a set of color filters, which result in the maximum number of good LCD assemblies. A simple mathematical model is constructed for this problem and an optimal solution can be obtained using an existing algorithm. The other is a main problem that requires a determination of an economic lot size of the color filters which are going to be assembled with a given set of TFT glasses. A Bayesian dynamic forecasting model is developed to predict the defective patterns of color filters. Based on the predicted defective rate of color filters, the minimum lot size of the color filters can be determined to minimize the probability of losing good TFT glasses and color filters.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 1999년도 High Temperature Superconductivity Vol.IX
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• pp.138-141
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• 1999

For the enhancement of communication system performance, high quality filters are required. Conventional metal filters made of copper can be substituted by high quality high temperature superconductivity(HIS) flms for better performance. In order to reduce the size of the filter for the integration of device in the limited area, we have fabricated hairpin type filters using pulsed laser deposition(PLD) technique. The superconducting YBCO thin films have been grown on MgO substrates by PLD with Nd:YAC laser. The YBCO films were patterned by conventional wet-etching process. We have compared YBCO filters and copper filters which were made with the same spec. Simulated and measured frequency responses reveal that HIS YBCO hairpin type bandpass filters show better performance than copper filters.

• 한국수자원학회논문집
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• 제56권2호
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• pp.139-150
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• 2023

지상 LiDAR 측량은 구조물이나 지형의 시간별 변형을 쉽게 파악할 수 있어 토목시설물의 유지관리에 활용성이 높다. 그러나 제방과 같은 하천시설물은 식생의 영향으로 식생 하부의 지형이나 구조물의 변형을 파악하기 어렵다. 식생 제거 필터는 색상필터와 형태필터로 구분할 수 있다. 본 연구에서는 식생필터의 정확도 향상을 위해 색상과 지형을 결합한 복합필터를 개발하였다. 8개의 색상필터, 6개의 지형필터, 4개의 복합필터를 제방 비탈면의 식생제거에 적용하여 정확도와 계산시간을 비교하였다. 색상필터는 계산시간은 짧으나 식생 영역에서 정확도가 낮게 나타났다. 형태필터는 식생 영역에서는 정확도가 높으나 거석 등 국부적 지형 변화가 심한 곳에는 정확도 낮게 나타났다. 복합필터도 대체로 지형필터와 유사한 경향을 나타내나 ExGGM의 경우 식생 영역과 거석 영역 모두에서 정확도가 우수하였다. 정확도와 계산시간을 고려하며 일반적인 경우에는 복합필터인 ExGGM이 적합하며, 국부적인 지형 변화가 심하지 않은 경우에는 형태필터인 GrMIn 또는 복합필터인 ExGISL이 적합한 것으로 나타났다.

• 한국산업보건학회지
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• 제27권4호
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• pp.283-290
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• 2017

Objectives: This study aimed to evaluate the relationship between filter replacement and filter performance change in particulate filters used in the workplace. Methods: Three types of particulate respirator filters are mainly used in the workplaces. These were tested against the filter performance safety certification standard for dust masks established by the Ministry of Employment and Labor(MoEL). Used filters were collected to test their performance, such as filter pressure drop, efficiency, and quality factors. All these factors were evaluated by a filter tester. To compare filter performance between used and new ones, the same kinds of new filters were also tested together under the same procedures. Results: A total of 270 used filters were collected for testing. The main reasons to replace the filters were difficulty in breathing(46.2%), dirty/odor influx(19.7%), and a combination of factors(26.7%). The pressure drop for two special class groups was significantly different(new filters: $20.72{\pm}3.33mmH_2O$; used filters: $24.70{\pm}5.26mmH_2O$, p<0.0001). In the case of penetration, new filter groups indicated $0.0032{\pm}0.0040%$, while that of the used filters was $0.0596{\pm}0.1187%$. The quality factor for the used filters($0.34{\pm}0.09$) significantly decreased compared to the new filters($0.53{\pm}0.08$) (p<0.0001). Conclusions: Filter performance including pressure drop, penetration, and the quality factor was evaluated and compared between new and used filters in the workplace. The results showed that general filter performance deteriorated more for change of pressure drop, penetration and the quality factor.

• 한국통신학회논문지
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• 제19권12호
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• pp.2458-2467
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• 1994

본 논문에서는 임의로 주어진 설계 조건을 만족하는 MF(Maximally Flat) FTR 저역통과필터 및 고역통과필터의 임펄스응답으로부터 직접적인 연산에 의해서 대역통과필터 및 대역저지필터의 임펄스응답을 구하였다. 또한 위상차가 없는 2-차원의 MF FTR 저역통과필터, 고역통과필터, 대역통과필터 및 대역저지필터는 본 연구에서 구한 1-차원의 임펄스응답의 변환에 의해서 구하였으며, 이러한 필터들은 영상신호처리 과정에서 발생할 수 있는 선과 모서리의 파괴를 방지할 수 있다.

• 한국환경보건학회지
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• 제29권2호
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• pp.69-76
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• 2003

Hexavalent chromium may reduce on polyvinyl chloride (PVC) filter during sampling and storage of sample. Recently, new or modified filters for preventing Cr(VI) from the reduction has been introduced. Thus, this study was performed to compare the reduction behaviors of Cr(VI) on several sampling filters and to find the most appropriate filter for airborne Cr(VI) sampling in plating operation. The results were as follows. 1. There were statistically significant differences among PVC, polytetrafluoroethylene (PTFE). glass fiber (GF) and polyvinylidene fluoride (PVDF) filters in recovery rates of spiked Cr(VI) samples by storage time(p<0.05). There was no significant difference between PVC and PTFE filters(p>0.05). The PVC and PTFE filters showed higher recoveries than GF and PVDF filters(p<0.05). 2. The quartz fiber(QF) filter treated with an alkali solution(2% NaOH/3% Na$_2$CO$_3$, 1% NaOH) showed a significantly higher recovery of Cr(VI) by storage time than other filters(GF and QF filter)(p<0.05). There was no difference in recovery of Cr(VI) between alkali-treated and untreated GF it filters(p>0.05). But the QF filters treated with two alkali solution showed a significantly higher recovery than the untreated QF filter(p<0.05). There was no significant difference in recovery of Cr(VI) between QF filters treated with 1% NaOH and 2% NaOH/3% Na$_2$CO$_3$(p>0.05). In conclusion, treatment of QF fillers with alkali solution was most effective in protecting from the reduction of Cr(VI).

• 신재생에너지
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• 제7권4호
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• pp.58-65
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• 2011

In variable-speed variable-pitch wind turbines, the conventional approach for controlling power-production operation relies on a generator-torque controller and a rotor-collective blade-pitch controller. Both controllers use the generator speed measurement as the sole feedback input. In order to mitigate unwanted excitation of the control system, many filters are adopted. In this study, the characteristics of some filters for signal processing are investigated based on frequency response function. They include low-pass filters, band-pass filters, and notch filters. Especially, this study focuses on design parameters of their filters.

• Journal of Electrical Engineering and Technology
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• 제4권3호
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• pp.423-428
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• 2009

In FIR (Finite Impulse Response) filter applications, Nth-band FIR digital filters are known to be important due to their reduced computational requirements. The conventional methods for designing FIR filters use iterative approaches such as the well-known Parks-McClellan algorithm. The Parks-McClellan algorithm is also used to design Nth-band FIR digital filters after Mintzer's research. However, a disadvantage of the Parks-McClellan algorithm is that it needs a large amount of design time. This paper describes a direct design method for Nth-band FIR Filters using Chebyshev polynomials, which provides a reduced design time over indirect methods such as the Parks-McClellan algorithm. The response of the resulting filter is equi-ripple in passband. Our proposed method produces a passband response that is equi-ripple to within a minuscule error, comparable to that of Mintzer's design method which uses the Parks-McClellan algorithm.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.475-479
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• 2001

Compensation characteristics or active filters based on voltage detection are investigated. These active filters act equivalently as a passive circuit so that they may not cause practical problems such as stimulation of resonance in the distribution lines. Thus, these active filters can be used as the general-purpose active filters. On the other hand, these active filters may have a possibility of the anti-resonance associated with the line inductance of the distribution lines. In this paper, the relationship between the anti-resonance and the control parameters of the proposed active filters is clarified. Some methods to avoid the problems due to the anti-resonance are investigated. Experimental results are included to confirm the validity of the investigation presented in this paper.

• 대한전기학회논문지:시스템및제어부문D
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• 제54권10호
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• pp.630-638
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• 2005

In FIR (Finite Impulse Response) filter applications, Nth-band F]U digital filters are known to be important due to their reduced computational requirements. The conventional methods for designing F]U filters use iterative approaches such as the well-known Parks-Mcclellan algorithm. The Parks-Mcclellan algorithm is also used to design Nth-band FIR digital filters. But a disadvantage of the Parks-Mcclellan algorithm is that it needs a good amount of design time. This paper describes a direct design method for Nth-band FIR Filters using Chebyshev polynomials, which provides a reduced design time over indirect methods such as the Parks-Mcclellan algorithm. The response of the resulting filter is equiripple in passband. Our proposed method produces a passband response that is equripple to within a minuscule error, comparable to that of the Parks-Mcclellan algorithm.