• 품질경영학회지
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• 제22권1호
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• pp.82-95
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• 1994

When independent individual measurements are taken both $S/c_4$ and $\bar{R}/d_2$ are unbiased estimators of the process standard deviation. However, with dependent data $\bar{R}/d_2$ is not an unbiased estimator of the process standard deviation. On the other hand $S/c_4$ is an asymptotic unbiased estimator. If there exists correlation in the data, positive(negative) correlation tends to increase(decrease) the ARL. The effect of using $\bar{R}/d_2$ is greater than $S/c_4$ if the assumption of independence is invalid. Supplementary runs rule shortens the ARL of X control charts dramatically in the presence of correlation in the data.

• 소성∙가공
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• 제25권5호
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• pp.332-337
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• 2016

The automobile cowl cross bar which is a backbone frame part holding electrical and air conditioning components inside the cockpit module has been designed with more complex geometries recently due to demands of its enhanced functions and reduced weight of frame parts. The traditional manufacturing process using welding between tubes with different diameters shows several problems such as poor mechanical characteristics and appearance, etc. Therefore, in this study, one-piece manufacturing processes which can eliminate the welding process were developed by applying the rotary swaging process. CAE analyses were conducted to examine the feasibility of the process and prototypes were manufactured by using a rotary swaging machine with 4 split rotating dies and 12 head rollers. Bending tests of the manufactured prototypes confirmed that the rotary swaging process gives better mechanical properties comparing with the conventional processes.

• 설비공학논문집
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• 제2권2호
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• pp.99-104
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• 1990

A Study has been conducted experimentally on heat transfer characteristics of louvered fin heat exchangers with various louvered positions in air. The experimental results are as follows; 1. Mean heat transfer coefficient is increased with increasing air velocity and decreasing temperature difference. The maximum value of heat transfer coefficient shows at 10㎜ backward louvered fins. 2. Pressure drop is increased with increasing air velocity and apparently depended on the louvered positions at V>10m/sec. 3. $\bar{h}/{\Delta}P$ is decreased with increasing air velocity and its maximum value shows at 10mm forward louvered fins and its minimum value shows at plate fins.

• 설비공학논문집
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• 제2권4호
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• pp.288-294
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• 1990

A study has been conducted experimentally on heat transfer characteristics of louvered fin heat exchangers with various fin spacings in air. The experimental results are as follows; 1. Mean heat transfer coefficient is increased with increasing air velocity and the optimum fin spacing shows at S=5mm. 2. Pressure drop is increased with increasing air velocity and its maximum value shows at S=3.5mm and its minimum value shows at S=6mm. 3. $\bar{h}/{\Delta}P$ is decreased with increasing air velocity and its maximum value shows at S=5mm and its minimum value shows at S=3.5mm.

• 소성∙가공
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• 제18권7호
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• pp.538-543
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• 2009

The cowl cross bar of an automobile is a frame component that is installed inside the cockpit module to provide a guide surface, to which functional components for electricity and air condition are attached. In the recent years, the geometries of cowl cross bars are getting more complex in order to meet the demands of a wide variety of embedded functional components and the reduced weight of frame parts with enhanced mechanical and noise/vibration characteristics. There for, welding processes between tubes with different diameters are widely conducted while the welded parts are experiencing various problems such as undermined appearance, low production efficiency and poor mechanical characteristics. Therefore, this paper seeks to develop an one-piece forming process which eliminate welding process for the cowl cross bar by applying the tube drawing process. However, it was predicted that a conventional tube drawing can not be applied directly to the current part since the area reduction ratio of the drawing process reaches 51.7% which exceeds the general limiting value. Therefore, in this study, a combined drawing process which adds a compressive force to a tensile force of the conventional drawing process was proposed and 2-stage drawing process was designed by using CAE analyses. In addition, drawing tryouts were carried out by using the manufactured combined drawing machine in order to verify the designed process.

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.15-16
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• 2005

In this study, the characteristics of NOx reduction by using charge air moisturizer system were evaluated by engine performance simulation in medium speed diesel engines. The results of performance simulation were verified by experimental results of single cylinder medium speed diesel engine equipped with charge air moisturizer system. Performance simulation was carried out to evaluate charge air moisturizer system of turbocharged diesel engine, HYUNDAI HiMSEN 9H25/33 engine. Those results show 50% NOx reduction at dew point $80^{\circ}C$ and charge air pressure 4bar.

• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.59-68
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• 2017

Mercury intrusion and nitrogen sorption porosimetry were employed to investigate the pore structure of calcium sulfoaluminate ($C{\bar{S}}A$) and portland cement pastes with cement-to-water ratio (w/c) of 0.40, 0.50, and 0.60. A unimodal distribution of pore size was drawn for $C{\bar{S}}A$ cement pastes, whereas a bimodal distribution was established for the portland cement pastes through analysis of mercury intrusion porosimetry. For the experimental results generated by nitrogen sorption porosimetry, the $C{\bar{S}}A$ cement pastes have a smaller and coarser pore volume than cement paste samples under the same w/c condition. The relative dynamic modulus and percentage weight loss were used for investigation of the concrete durability in freeze-thaw condition. When coarse aggregate with good freeze-thaw durability was mixed, air entrained portland cement concrete has the same durability in terms of relative dynamic modulus as $C{\bar{S}}A$ cement concrete in a freeze-thaw environment. The $C{\bar{S}}A$ cement concrete with poor performance of durability in a freeze-thaw environment demonstrates the improved durability by 300 % over portland cement concrete. The $C{\bar{S}}A$ concrete with good performance aggregate also exhibits less surface scaling in a freeze-thaw environment, losing 11 % less mass after 297 cycles.

• 한국태양에너지학회 논문집
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• 제32권spc3호
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• pp.207-212
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• 2012

It is important to produce the high-temperature and high-pressure air for the concentrated solar power system using the combined cycle. In this paper, we designed two types of tubular receivers to heat up the compressed air and provided their preliminary experimental results for performance evaluation and further improvements. The developed receivers are in a square cavity shape surrounded by flow conduits for easy scale-up and radiation loss reduction. The two receivers were tested with 5 bar air in the KIER solar furnace and evaluated in terms of the outlet temperature and the efficiency.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2002년도 유체기계 연구개발 발표회 논문집
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• pp.177-182
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• 2002

In the paper, the development of high-speed industrial turbo blowers with foil air bearings is presented as a first successful commercialization in the world. Their target market is various from wastewater treatment to cement factory processes which require compressed air ranging between 0.6 and 0.8 bar gauge. Employing the state-of·the-art technology of the high-speed BLDC motors, the bump-type foil air bearings and the high- efficient turbo impellers/diffusers, so much compact, efficient and silent blower machines of a single stage are now available in the market, aiming to replace the existing inefficient, bulky and noisy ones, such as roots blowers. The first production lines are established fur 25,75 and 150 hp class blowers. Rotational speeds from about 20,000 to 80,000 rpm are realized directly from the high-speed BLDC motors without any gear boxes, and no lubrication oil is required. A brief introduction of design, manufacture and test results is presented fur mechanical, electrical and aerodynamic performance.

• 한국컴퓨터정보학회논문지
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• 제12권6호
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• pp.297-306
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• 2007

항공 화물 수요의 증가 및 정보 기술의 발달로 인해 새로운 항공 물류 시스템의 필요성이 대두되고 있다. 기존 바코드 기반의 항공 물류 시스템은 수작업 위주의 화물 처리와 개별적인 화물 정보 시스템으로 인해 화물 분실, 관리 오류, 화물 데이터 공유의 어려움과 같은 많은 문제점을 야기하고 있다. 이를 위해 본 논문은 실제 항공 화물 처리 프로세스를 분석하여 이를 바탕으로 RFID 기반의 항공 물류 시스템을 설계하고 구현하였다. 이 시스템은 RFID 장치로부터 발생된 화물 정보를 실시간으로 수집, 가공하여 정보 서비스 시스템에서 관리하며 캡처 응용프로 그램 및 액세스 응용 프로그램으로부터의 데이터 쿼리를 처리하여 화물 추적, 이벤트조회와 같은 다양한 서비스를 제공한다. 또한 기존 바코드 시스템과의 통합을 위한 이동형 리더 관리자를 포함한다. 이를 통해 물류 프로세스의 자동화 및 정보화를 실현하고 화물 분실 및 관리 오류를 감소시켜 항공 물류 서비스의 질적 향상을 이룬다.