• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.12
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• pp.1613-1618
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• 2012

The wheel bearing is one of the important parts in a vehicle for translating power and bearing weight. When it is mounted on the knuckle by using bolts, the distortion of the outer ring including the seal mounting point and raceway occurs. In this study, a numerical analysis was performed to analyze the distortion of the outer ring by using a finite element method. The commercial software MSC.MARC was used for this purpose. Elastoplastic and contact analysis were carried out to compute the clamping behavior of the outer ring, bolts, and knuckle. Because the concavity on the flange of the outer ring affects the deformation, its effect was considered. To verify the reliability of this study, the roundness of the outer ring was measured. The experimental results were comparatively in agreement with the computational results.

• The Plant Pathology Journal
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• v.20 no.2
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• pp.81-84
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• 2004

Branched broomrape (Orobanche ramosa) is a holo-parasitic flowering plant that attaches to the root of its host, green plant, by means of a specialized structure known as haustorium. Following successful contact and penetration on susceptible plant root, complex tissue of Orobanche cells is formed which is known as the tubercle. Newly formed tubercles contain high activity ofindole-3-acetic acid (IAA). Triiodobenzoic acid (TIBA), as an inhibitor of IAA polar transport, was utilized to investigate the supply and requirement of auxin to the developing O. ramosa on tomato plant. There was no significant reduction in the incidence of O. ramosa per pot of different TIBA treatments. However, infection severity in terms of the number of O. ramosa shoots that emerged per plant and number of attachments per plant root system were significantly reduced by 60 % and 45 % on TIBA treated plants, respectively. Histo-logical studies revealed conspicuous delay in the initiation of xylem vessel differentiation inside tubercles of the TIBA treated tomato plants. Also, differentiated vessels showed thinner secondary wall deposition, and improper alignment within bundles inside those tubercles. They were wider and shorter in diameter in comparison to those of untreated plants. These findings were attri-buted to the short supply of IAA required for normal development, and to the xylem vessel differentiation of O. ramosa tubercles on infected tomato. Hence, this parasitic flowering plant seems to depend upon its host in its requirements for IAA, in a source to sink relation-ship.

• Toxicological Research
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• v.6 no.2
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• pp.159-166
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• 1990

The ability of many toxigenic fungi to invade and develop in a wide variety of raw ingredients of human diet renders human exposure to mycotoxing very difficult to avoid. Most of the energy-rich commodities, such as cereal grains, oil seeds, tree nuts, and dehydrated fruits, are susceptible to mycotoxin contamination. Mycotoxins therefare have been recognized as an important class of hazardous substances in the human food chain. Although human exposure to mycotoxins is largely through ingestion, inhalation and skin contact may also be significant under conditions other than consumption of foods. Human ingestion of mycotoxins is due to consumption of contaminated dietary ingredients and the edible tissues and products of domestic animals that have been exposed to mycotoxins in moldy feed. Large scale acute human mycotoxicoses, such as ergotism in France, alimentary toxic aleukia in Russia, yellow rice syndrome in Japan, endemic nephropathy in Balkan countries, and acute aflatoxin poisonings in India and Taiwan, have been well documented, indicating that mycotoxicosis is a global problem. In some incidents, hundreds of victims were killed and many more became seriously ill. The mycotoxins that have been implicated in the etiology of these human diseases include aflatoxins, citreoviridin, cyclopiazonic acid, ergot alkaloids, moniliformin, ochratoxin A, trichothecenes, tenuazonic acid, and zearalenone. Among these, aflatoxins have been also implicated in the etiology of human primary liver cancer in those high-incidence countries in Africa and southeast Asia. It is well recognized that cause-effect relationship between mycotoxins and human diseases is very difficult to establish, especially for the cancer connection. Careful risk assessment must be performed to determine whether a mycotoxin indeed warrants costly regulatory actions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.1033-1036
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• 2002

Wafer bonding methods such as fusion and anodic bonding suffer from high temperature treatment, long processing time, and possible damage to the micro-scale sensor or actuators. In the localized bonding process, beating was conducted locally while the whole wafer is maintained at a relatively low temperature. But previous research of localized heating has some problems, such as non-uniform soldering due to non-uniform heating and micro crack formation on the glass capsule by thermal stress effect. To address this non-uniformity problem, a new heater configuration is being proposed. By keeping several points on the heater strip at calculated and constant potential, more uniform heating, hence more reliable wafer bonding could be achieved. The proposed scheme has been successfully demonstrated, and the result shows that it will be very useful in hermetic packaging. Less than 0.2 ㎫ contact Pressure were used for bonding with 150 ㎃ current input for 50${\mu}{\textrm}{m}$ width, 2${\mu}{\textrm}{m}$ height and 8mm $\times$ 8mm, 5mm$\times$5mm, 3mm $\times$ 3mm sized phosphorus-doped poly-silicon micro heater. The temperature can be raised at the bonding region to 80$0^{\circ}C$, and it was enough to achieve a strong and reliable bonding in 3minutes. The IR camera test results show improved uniformity in heat distribution compared with conventional micro heaters. For gross leak check, IPA (Isopropanol Alcohol) was used. Since IPA has better wetability than water, it can easily penetrate small openings, and is more suitable for gross leak check. The pass ratio of bonded dies was 70%, for conventional localized heating, and 85% for newly developed FP scheme. The bonding strength was more than 30㎫ for FP scheme packaging, which shows that FP scheme can be a good candidate for micro scale hermetic packaging.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.10
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• pp.1155-1162
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• 2012

The purpose of this study is to investigate the effects of the bead shape on the crash performance of an aluminum crash box under a low-velocity impact condition. The initial peak load and impact energy absorption of a crash box with three types of bead shapes-edge concave, surface convex, and surface concave type-were studied through an FE analysis and an experiment. In addition, the effects of the bead shapes on the crash performance of the crash box were verified through a low-velocity-impact test with a front side member assembled with an aluminum crash box. The initial peak load of the surface-concave-type crash box was reduced by the bead, and therefore, deformation of the front side member at initial contact could be prevented. Furthermore, there was no deformation of the front side member after the impact test because the crash box with a surface-concave-type bead absorbed all the impact energy.

• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.4
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• pp.373-379
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• 2010

EMAT has been applied in various fields for flaw detection and material characterization because it has noncontact property in wave generation and a good mode selectivity. Unfortunately, however, EMAT shows low signal to noise ratio relative to commercial contact transducer because of low energy conversion efficiency. If the phase matching through the control of time delay between each coil consisting of the array EMAT is accomplished, it is expected that it will be a solution for the improvement of low signal to noise ratio. In this experiment, the phased array EMATs which consists of 3 or 4 meander coils and one big magnet were fabricated for surface and vertical shear wave generation. Effect of phased delay control on signal directivity and amplitude enhancement was verified. A slit with the depth of 0.5 mm and a side-drill hole of 0.5 mm diameter were clearly detected by fabricated phased array EMATs, respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.380-383
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• 2006

The media transport system is used in a printer, a ATM(Automated Tellor Machine), and so on. The media transport system has many problems through miniaturization and rapid transportation of these machines. In the paper feeding mechanism, it is important to feed the sheet without jamming under any conditions. To avoid sheet jamming, first we need to predict the behavior of the sheet exactly. In this paper, the analysis of media behavior is based on J. Stolte's studies. In all of OA machines, a flexible beam or plate is pushed from the channel. The motion may be constrained by guides. This leads to a transient and geometrically nonlinear problem. The behavior of paper is simulated by dynamic elastica theory. The shape of guide is represented by parametric cubic curve. But J. Stolte's studies did not considered contact condition between sheet and guide. So Klarbring's Model. will be applied. And the analysis of flexible media has to include aerodynamic effect for more exact behavior analysis, because the flexible media can be deformed drastically by a little force. Therefore aerodynamic force must be applied to the governing equation. Lastly, the simulation of this model is performed, and the experiment is performed for verification of this model. The experimental results of low exit velocity are consistent with the simulation results, however experimental results of high exit velocity do not agree well with analytical results. The reason is that there may be other effects like nip Phenomena

• Proceedings of the Korean Vacuum Society Conference
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• 2012.02a
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• pp.389-389
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• 2012

Molybdenum is one of the most important materials used as a back ohmic contact for $Cu(In,Ga)(Se,S)_2$ (CIGS) solar cells because it has good electrical properties as an inert and mechanically durable substrate during the absorber film growth. Sputter deposition is the common deposition process for Mo thin films. Molybdenum thin films were deposited on soda lime glass (SLG) substrates using direct-current planar magnetron sputtering technique. The outdiffusion of Na from the SLG through the Mo film to the CIGS based solar cell, also plays an important role in enhancing the device electrical properties and its performance. The structure, surface morphology and electrical characteristics of Mo thin films are generally dependent on deposition parameters such as DC power, pressure, distance between target and substrate, and deposition temperature. The aim of the present study is to show the resistivity of Mo layers, their crystallinity and morphologies, which are influenced by the substrate temperature. The thickness of Mo films is measured by Tencor-P1 profiler. The crystal structures are analyzed using X-ray diffraction (XRD: X'Pert MPD PRO / Philips). The resistivity of Mo thin films was measured by Hall effect measurement system (HMS-3000/0.55T). The surface morphology and grain shape of the films were examined by field emission scanning electron microscopy (FESEM: Hitachi S-4300). The chemical composition of the films was obtained by the energy dispersive X-ray spectroscopy (EDX). Finally the optimum substrate temperature as well as deposition conditions for Mo thin films will be developed.

• Korean Journal of Materials Research
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• v.9 no.9
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• pp.890-895
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• 1999

The recent important issue in solar cell fabrication is to adopt thin film silicon solar cells on cheap substrates. However, thin cells demand new grid design concept that all the contacts(to the emitter and base) be located on the front surface. Hence, the aim of the investigation presented in this paper was to determine the potential and the basic limitation of the design. With this concept, an interdigitated front grid structure was realized and cells were fabricated through a set of photolithography processes. Confirmed efficiencies of up to 11.5% were achieved on bonded SOI wafers with a cell thickness of 50$\mu\textrm{m}$ in the case of finger spacing more than $\mu\textrm{m}$ and a base width of 35$\mu\textrm{m}$. It was also shown from the results that the design rules for optimizing the base fraction and reducing the shadowing fraction are noted as an important technique to realize high-efficiency thin silicon solar cells.

• Korean Journal of Materials Research
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• v.25 no.5
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• pp.233-237
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• 2015

Silicon oxynitride that can be deposited two times faster than general SiNx:H layer was applied to fabricate the passivation protection layer of atomic layer deposition (ALD) $Al_2O_3$. The protection layer is deposited by plasma-enhanced chemical vapor deposition to protect $Al_2O_3$ passivation layer from a high temperature metallization process for contact firing in screen-printed silicon solar cell. In this study, we studied passivation performance of ALD $Al_2O_3$ film as functions of process temperature and RF plasma effect in plasma-enhanced chemical vapor deposition system. $Al_2O_3$/SiON stacks coated at $400^{\circ}C$ showed higher lifetime values in the as-stacked state. In contrast, a high quality $Al_2O_3$/SiON stack was obtained with a plasma power of 400 W and a capping-deposition temperature of $200^{\circ}C$ after the firing process. The best lifetime was achieved with stack films fired at $850^{\circ}C$. These results demonstrated the potential of the $Al_2O_3/SiON$ passivated layer for crystalline silicon solar cells.