• 한국자동차공학회논문집
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• 제6권6호
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• pp.24-30
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• 1998

A directly coupled Boundary Element and Finite Element Model was applied to the dynamic analysis of a coupled acoustic silencer with vibratory wall. In this cupled BEM-FEM muffler model, the BEM model was used to discretize the acoustic cavity and the FEM model was used to discretize the vibratory wall structure. Then the BEM model was coupled with the FEM model. The results of the coupled BEM-FEM model for the dynamic analysis of the simple expansion type reactive muffler configurations with flexible walls were verified by comparing the predicted results to analytical solutions. In order to investigate the effects of the muffler's structural flexibility on its transmission loss(TL) characteristics, the results of the coupled BEM-FEM model in conjunction with the four-pole parameter theory were utilized. The muffler's TL characteristics using the BEM-FEM coupled model with flexible walls as compared to other muffler configurations was studied. Finally the muffler's TL values with respect to different wall's thickness are predicted and compared.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 춘계학술대회논문집
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• pp.346-352
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• 2002

This paper is the experimental study to estimate the influence of various design parameters on the performance of mufflers with perforated tubes and through-flow partitions. Muffler types considered in the present work include through-flow chamber, through-flow chamber with partition, and cross-flow chamber. The influences of the design parameters on the performance of the mufflers can be outlined as follows. In the case of the through-f]ow type mufflers, increasing the tube thickness and the hole diameter of the perforated tubes does not change the maximum value of the transmission loss but decrease the cutoff frequency. In the case of the through-flow with partitions type mufflers, it is shown that combining a fe w short chambers and long chambers can modify the frequency locations of the resonance frequencies to optimize the performance of the mufflers. For the case of the cross-flow type mufflers, it is shown that the transmission loss of the mufflers is mainly affected by the lower porosity when the porosities are different in both sides of the plug. Overall, it is shown that performance of the through-flow type with partition type mufflers is excellent in the lower frequency region, where the cross-flow type mufflers have better performance in the higher frequency region.

• 한국환경과학회지
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• 제29권5호
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• pp.519-529
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• 2020

The purpose of this study was to provide basic health care data for the climate aspects of park re-cultivation by evaluating air ions according to the type of vegetation in the valley and upper slopes of the mountain park. Simple negative or positive air ions were expected to show the same tendencies, so they were analyzed in terms of correcting the air ion index. By analyzing the air ions according to the topography, it was found that valley > slope in terms of the air ion index. When analyzing air ions according to tree species, we found that evergreen conifers in the valley > the deciduous broad-leaved trees in the valley > the evergreen conifers in the slope = the deciduous broad-leaved trees in the slope. For DBH(Diameter at breast height), the valley large pole > slope large pole > slope medium hard wood, while crown density was analyzed as valley dense > slope dense> valley proper > slope proper. Layered structure analysis showed that the multi-layer structure of the valley > multi-layer structure of the slope = the single-layer structure of the valley > the single-layer structure of the slope. The correlation coefficient was determined according to vegetation type and air ion index in the order of DBH > crown density > layer structure > geomorphic structure. In this study, limits exist except for ridge line, valley, and slopes in urban mountain parks. Therefore, analysis should be made considering both topographical structure and various vegetation types in future studies of air ions.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2007년도 제38회 하계학술대회
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• pp.1185-1186
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• 2007

The UTM-01 developed in 1998 was the first maglev vehicle in Korea for the urban transit maglev (UTM) system. Through the improvement of UTM-01 and development of UTM02, the commercialization of the UTM system is being prepared now. In order to prepare for the commercialization of maglev, it is necessary that an optimal design of the levitation magnet should be provided for the safe operation of the vehicle. The levitation force is formed through the function of magnetic flux density on the top of magnet poles and gap between magnet pole and guide rail. To generate a magnetic field that is high enough to levitate the vehicle, ferromagnetic materials, such as pure iron for magnet pole and SS400 for guide rail, were used. The heat generated by $I^2R$ loss of magnet conductor makes the thermal convection on the surface of magnet including coil and poles. As these two characteristics are nonlinear phenomena, this paper deals with the nonlinear analysis on the magnetic and thermal properties of the U-type levitation magnet by using 3-D finite element method (FEM). Base on the analysis results, a small scale U-type magnet was designed, manufactured, and tested and it was verified that the magnet manufactured was satisfactory to all the design specifications.

• Progress in Superconductivity
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• 제2권2호
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• pp.92-96
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• 2001

We have fabricated a modified hairpin-type YBa$_2$Cu$_3$O$_{7-{\delta}}$ (YBCO) 2-pole microstrip bandpass filter with the center frequency of 5.8 GHz. We designed a hairpin-type filter with interdigital-coupled inner poles to improve the filter performance. Compared to a typical hairpin-type filter of the same size, the center frequency, the bandwidth and the insertion loss appeared smaller by 14.5% ,29.6%, and 0.55 dB, respectively. The dimensions of the filter were 13.7mm ${\times}$3.3 mm. YBCO films deposited on r-cut sapphire buffered with a CeO$_2$thin layer were used fur making the filter.

• 한국ITS학회 논문지
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• 제17권6호
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• pp.185-201
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• 2018

야간 도로를 주행하는 운전자의 안전을 위한 대표적인 대책으로 등주식 도로조명의 설치가 선호되고 있다. 그러나 기존 등주식 형태 도로조명의 경우 노면으로부터 일정 높이에 설치되는 특성으로 인해 광원이 운전자에게 직접적으로 강한 눈부심을 주어 운전자의 시인성을 저해하고, 도로 외의 지역에도 빛이 누설되어 에너지 효율이 떨어질 뿐 아니라 주거지역이나 동식물에 장해를 주는 빛공해가 발생하게 된다. 이러한 문제점을 해소한 낮은 위치에 설치되어 조명이 도로만을 비추는 형태의 낮은 조명이 해결책으로 제안되고 있으나, 도입 초기인 낮은 조명이 도로조명등급을 만족하여 도로조명으로서의 역할을 할 수 있는지에 대한 연구는 부족한 실정이다. 따라서 본 연구는 도로조명으로서 요구되는 최소한의 시인성능 기준을 만족함과 동시에 빛공해를 근본적으로 차단할 수 있는 구조의 낮은 조명을 개발하고 기존 등주식 조명과 시인성능 비교를 수행한 결과를 제시하였다. 비교결과, 기존 등주식 조명에 비해 평균노면휘도, 균제도, 임계치 증분 평가에서 우수한 결과를 나타냈다.

• 한국전통조경학회지
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• 제39권3호
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• pp.56-64
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• 2021

정자는 전통 조경에서 중요한 경관적 장치이자 공간을 구성하는 대표적인 시설이다. 전통 조경공간에 대한 해석과 계승을 위해서는 전통 정자의 형상과 구조에 대한 연구도 동반되어야 한다. 하지만 전통 정자의 양식과 구조에 관한 연구는 찾아보기 어렵다. 이에 본 연구는 정자의 형상을 결정짓는데 가장 비중이 큰 지붕부를 대상으로 구조적 특성의 규명을 목적으로 하였다. 연구결과는 다음과 같다. 구조를 파악할 수 있는 15개의 한칸형 전통 사각정자를 대상으로 분석한 결과 한 칸 정자의 지붕부의 유형을 구분짓는 주요 부재는 보, 종도리, 동자임을 확인하였다. 지붕 부재의 유무에 따라 정자는 보, 보+종도리보+동자, 종도리, 동자 등 5가지 유형으로 분류되었다. 또한 지붕부의 형상 분류를 토대로 보에 작용하는 하중과 결구를 분석한 결과 한칸형 전통 사각정자에서 보가 수장과 하중의 균형을 이루는 역할을 하기 위한 것임을 확인하였다. 본 연구는 정자 지붕부의 형태와 부재의 역할과 기능에 대해 크기, 비율, 하중 등으로 면밀하게 해석을 시도하였다는 점에서 의의가 있다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권2호
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• pp.137-141
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• 2005

A transverse flux, PM-exited linear motor (TFM-LM) with inner mover was designed and built. Its output power density is higher and its weight is lower than those of the conventional PM exited linear synchronous motors (PM LSM). To obtain the maximum thrust force under the given volume, the thrust force density with respect to the ratio of the slot width and the length of pole pitch is analyzed by the 3-dimension finite element method (FEM). Finally, calculated static thrust forces was compared with the experimental values. The calculated and measured performance of the transverse flux, PM-exited linear motor with inner mover revealed great potential for system improvements by reducing the mass of the linear motor. For examples, when this motor was applied to a ropeless elevator, it was possible to increase the power density by more than 400% over the conventional PM-LSM. The results of this study recommend this type of motor for the ropeless elevator or gearless direct linear driving system.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1990년도 추계학술대회 논문집 학회본부
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• pp.32-36
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• 1990

LPM is a characterized motor to reciprocate linear motion for the office automation(OA), the factory automation(FA) and the field of information instruments because it can generate direct drive without any mechanical converter. For the design and analysis of permanent magnet type linear, pulse motor, it is therefore necessary to investigate the characteristics of magnetic flux distribution, static and dynamic thrust force, normal force, etc, by analyzing its magnetic circuit. This paper describes various useful methods for improving the characteristics of LPM. And these method is adopted on the PM and flat type, double side 2-phase 8-pole LPM.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1993년도 추계학술대회 논문집
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• pp.321-327
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• 1993

In order to maintain the cutting force at a desired level during peripheral end milling processes in spite of variation of the depth of cut and other machining conditions, a feedrate override. Apaptive Control Constraint (ACC) system are developed. Feedrate override was accomplished by a developed MMC board and PMC interface techniques. Nonlinear model of the cutting process was linearized as an adaptive model with time varying paramrters. Integral type estimators were introduced for on-line identification of cutting and control parameters in peripheral and milling processes. Zero Order Jold (ZOH) type degital control methodology which uses pole-placement concepts was applied for the ACC system. Performance of the developed ACC system was confirmed on the vertical machining center equipped with FANUC OMC for a large amount of experiment