• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2005년도 후기학술대회논문집
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• pp.13-14
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• 2005

Multi-dimensional combustion analysis and experiment has been carried out to investigate the effects of the injector nozzle hole diameter and number on the NOx formation and fuel consumption in HYUNDAI HiMSEN engine. The behavior of spray and combustion phenomena in diesel engine was examined by FIRE code. Wave breakup and Zeldovich models were adopted to describe the atomization characteristics and NOx formation. Wallfilm model suggested by Mundo, et al. and auto-ignition model suggested by Theobald and Cheng were adopted to investigate the spray-wall interaction characteristics and ignition delay. The information of spray angle and spray tip penetration length was extracted from fuel spray visualization experiment and the fuel injection rate profile was extracted from fuel injection system experiment as an input and verification data for the combustion analysis. Next, the nine different nozzle configurations were simulated to evaluate the effect of injector hole diameter and number on the NOx formation and fuel consumption.

• International Journal of Precision Engineering and Manufacturing
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• 제7권3호
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• pp.18-23
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• 2006

The formation degree of sustain (ITO pattern) determines the quality of a PDP (Plasma Display Panel). Thus, in the present study, we attempt to detect 100% of the defects that are larger than $30{\mu}m$. Currently, the inspection method in the PDP manufacturing process is dependent upon the naked eye or a microscope in off-line mode. In this study, a prototype inspection system for PDP ITO patterned glass is developed. The developed system, which is based on a line-scan mechanism, obtains information on the defects and sorts the defects by type automatically. The developed inspection system adopts a multi-vision method using slit-beam formation for minimum inspection time and the detection algorithm is embodied in the detection ability. Characteristic defects such as pin holes, substances, and protrusions are extracted using the blob analysis method. Defects such as open, short, spots and others are distinguished by the line type inspection algorithm. It was experimentally verified that the developed inspection system can detect defects with reliability of up to 95% in about 60 seconds for the 42-inch PDP panel.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 제3회 압연심포지엄 논문집 압연기술의 미래개척 (Exploitation of Future Rolling Technologies)
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• pp.403-411
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• 1999

The steel plate for shadow mask is used in a Cathode-ray tube of TV monitor and is the strictest product in surface quality because hundreds thousand of holes are perforated in a plane of 25 ${\times}$25 inches. To mass-produce this product, a reversible cold rolling mill for silicon steel was used and the rolling technology and the activity for quality improvement are described in this work. Because the steel plate is a mild steel, which is very sensitive to strip-breakage even in a low tension, we reset the minimum tension values matching to the operating conditions. The roll mark due to the multi-segmented araangement of shape controlling roll was prevented by hardening the intermediate shape controlling roll and by changing the existing working-roll into a HSS (Hig Speed Steel) roll. The scratch caused by the speed difference between a idle roll and a strip was prevented by increasing the roll roughness. With these activities, the steel plate for shadow mask can be stable. The continuous improvement of quality is, however, required for the customer satisfaction both of domestic and overseas market.

• 한국소음진동공학회논문집
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• 제17권10호
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• pp.958-966
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• 2007

This study presents full vehicle dynamics model for the dynamic characteristic analysis of chassis parts which are suspension and brake system. This vehicle dynamics model is appled to kinematics and quasi-static analysis for each chassis part. In order to develop the vehicle dynamics model, the parameters of each chassis element part which are bush, spring and damper are measured by experiment. Also the wheel forces and moments of 6 DOF are measured at each wheel center. These data are applied to input parameter for vehicle dynamics model. And the verification of the developed model is achieved to comparison with the experimental force data of spring, trailing arm and assist arm by using the load response by strain gauge. These experimental force data are acquired by road test at event surfaces of P/G which are belgian and chuck holes roads.

• International Journal of Automotive Technology
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• 제5권1호
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• pp.9-16
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• 2004

An experimental study was carried out to characterize the spray atomization process of micro-machined port fuel injectors with a piezoelectric atomization device, which can generate pressure pulsations through vibration of a piezoelectric transducer. In this study, several types of micro-machined arrays such as 30∼200-microns of hole arrays were tested. Both a dual-stream and a central-port injectors with micro-machined arrays were tested and compared with normal port fuel injectors. The spray visualization was conducted to characterize overall spray structure and phase Doppler particle analyzer (PDPA) system was used to quantify the droplet size and velocity. In addition, the pressure history was recorded by using digitized signal from pressure transducer. The results showed that modulation is effective to the spray atomization for tested injectors and atomization performance depends on injector design factors, orifice sizes, and frequency and power of the modulator. A number of resonance frequencies of the modulator was modified by injector parameters and temperature. In addition, our results suggested that design of sufficient space among holes is critical to avoid droplet coalescence in the multi-hole micro-machined injectors.

• 한국분말재료학회지
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• 제24권4호
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• pp.275-278
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• 2017

In the present work, we apply a technique that has been used for the expansion of graphite to multiwall carbon nanotubes (MWCNT). The nanotubes are rapidly heated for a short duration, followed by immersion in acid solution, so that they undergo expansion. The diameter of the expanded CNTs is 5-10 times larger than that of the as-received nanotubes. This results in considerable swelling of the CNTs and opening of the tube tips, which may facilitate the accessibility of lithium ions into the inner holes and the interstices between the nanotube walls. The Li-ion storage capacity of the expanded nanotubes is measured by using the material as an anode in Li-ion cells. The result show that the discharge capacity of the expanded nanotubes in the first cycle is as high as 2,160 mAh/g, which is about 28% higher than that of the un-treated MWCNT anode. However, the charge/discharge capacity quickly drops in subsequent cycles and finally reaches equilibrium values of ~370 mAh/g. This is possibly due to the destruction of the lattice structures by repeated intercalation of Li ions.

• 식물분류학회지
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• 제41권2호
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• pp.103-107
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• 2011

가지과 Withania somnifera (L.) Dunal의 종자 해부학적 특징을 알기 위하여 광학현미경과 주사전자 현미경을 사용하여 관찰하였다. 종자의 색깔은 노랑색이고, 종자의 형태는 신장형이며, 크기가 2−3 mm 정도이다. 종자는 종의를 가지고 있지 않았으며, 배유가 잘 발달한 유배유종자였다. 종피형태는 외종피외층형으로 나타났다. 종피는 외종피만으로 구성되는 단주피성 이었으며, 한 층의 외종피외층, 여러 층의 외종피중층, 그리고 한 층의 외종피내층으로 구성되었다. 그러나 종자가 완전히 성숙했을 때는 외종피중층이 모두 압착되었으며, 외종피외층은 특징적으로 파상형의 후벽세포로 발달하였다. 종피의 표면은 망상구조를 가지며, 수층 벽구조는 파상형으로 발달하였고, 표면에 여러 개의 구멍이 발달하는 특징이 관찰되었다.

• 천문학회보
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• 제39권1호
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• pp.37.1-37.1
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• 2014

There exists strong evidence supporting the co-evolution of central supermassive black holes and their host galaxies; however it is still under debate how such a relation comes about and whether it is relevant for all or only a subset of galaxies. An important mechanism connecting AGN to their host galaxies is AGN feedback, potentially heating up or even expelling gas from galaxies. AGN feedback may hence be responsible for the eventual quenching of star formation and halting of galaxy growth. A rich multi-wavelength dataset ranging from the X-ray regime (Chandra), to far-IR (Herschel), and radio (WSRT) is available for the North Ecliptic Pole field, most notably surveyed by the AKARI infrared space telescope, covering a total area on the sky of 5.4 sq. degrees. We investigate the star-formation properties and possible signatures of radio feedback mechanisms in the host galaxies of 237 radio-AGN below redshift z=2 and at a radio 1.4 GHz flux density limit of 0.1 mJy. Using broadband SED modeling, the nuclear and host galaxy components of these sources are studied simultaneously as a function of their radio luminosity. Here we present results concerning the AGN content of the radio sources in this field, while offering evidence supporting a "maintenance" type of feedback from powerful radio-jets.

• 한국신뢰성학회지:신뢰성응용연구
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• 제8권4호
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• pp.155-166
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• 2008

PTH cracks are caused by the mismatch of coefficient of thermal expansion(CTE) between polymer and laminated materials, and are one of the main failure mechanisms of multi layer boards. In spite of its importance, it is usually hard to measure or detect them because of its small size and invisibility. To detect PTH cracks more effectively, this paper proposes a theoretical model that can estimate the resistance value from crack size of PTHs. Using four-point probe resistance measurement method, the resistance value of test coupons is measured. Through measured data, we verify the validity of the proposed theoretical model and set up criteria of failure.

• 한국산학기술학회:학술대회논문집
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• 한국산학기술학회 2004년도 춘계학술대회
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• pp.42-46
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• 2004

네일 파일(nailfile)을 제조할 때 재료는 강판(두께 0.5mm)을 사용하고 가공방법은 외형형상을 만들고 $\phi$ 0.8-$\phi$ 1.0mm의 구멍을 약 300여개 뚫어 완성한다. 이들의 가공방법은 에칭(etching)에 의존하므로 제조 원가의 $33\%$를 에칭비가 차지하고 있으므로 제조원가의 상승원인이 되고 에칭시 부식제(etching reagent)의 잔류도 환경친화적이 못되며 재료가 강판이기 때문에 제품에 녹(rust)이 생기므로 이들의 문제점을 해결하고자 하였다. 따라서, 재질은 스테인리스판으로 교체하고 에칭가공 대신 금형으로 가공할 수 있는 프로그레시브 퍼퍼레이팅 금형(progressive perforating die)을 개발하였다.