• Design & Manufacturing
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• 제12권2호
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• pp.40-45
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• 2018

Recently, in construction equipment machinery production, development has focused on environmentally-friendly functions to improve existing production capacity. For excavators as well, emphasis has been placed on response to environmental regulations, miniaturization, and noise reduction, while technology is being developed considering cost reduction and safety.Accordingly, the front support, an inner reinforcement part of the excavator, as well as high-strength steel plates to improve safety and reduce weight, are being applied.However, in the case of high-strength materials, Springback occurs in the final formed part due to high residual stress during product forming. Derivation of a forming or product shaping process to reduce springback is needed. Accordingly, regarding the front support, an inner reinforcement part of the excavator, this study derived a method to improve springback and secure shape stiffness through analysis of the springback occurrence rate and springback causes through a forming analysis.As for the results of analyzing the springback occurrence rate of existing products through forming analysis, springback of -22.6 mm < z < 27.35 mm occurred on the z-axis, and it was confirmed that springback occurred due to the stiffness reinforcing bead of the upper and middle parts of the product.To control product residual stress and springback, we confirmed a tendency of springback reduction through local pre-cutting and stiffness reinforcement bead relocation.In the local pre-cutting model, springback was slightly reduced by 5.3% compared with the existing model, an insignificant reduction effect. In the stiffness reinforcement bead relocation model, when an X-shaped stiffness reinforcement bead was added to each corner portion of the product, springback was reduced by at least 80%.The X-shaped bead addition model was selected as the springback reduction model, and the level of stiffness compared to the existing model was confirmed through a structural analysis.The X-shaped bead additional model showed a stress springback of 90% and springback reduction of 7.4% compared with the existing model, indicating that springback and stiffness will be reinforced.

• Design & Manufacturing
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• 제12권1호
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• pp.52-57
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• 2018

With the recent strengthening of environmental regulations and the need for cost reduction, excavators, a type of construction equipment, are being miniaturized while components are being developed in consideration of stability. In the case of excavator press parts, mainly high-strength steel sheets are being used to enhance stability and reduce weight. However, in the case of high-strength materials, there is a need to research product forming methods to reduce Springback in defects arising in parts assembly due to Springback that result from the internal residual stress that occurs in press forming being released after product forming. Accordingly, regarding the tank cover, an excavator press-forming part, this study selected a method to reduce distortion through analysis of the Springback occurrence rate and Springback causes through a forming analysis. A forming analysis was conducted for the Springback of the tank cover. Deformations of 13.714 mm in the upper part and 6.244 mm in the inner part of the product occurred, while wrinkles occurred on the sides of the product due to uneven thickness. A forming analysis was conducted for the major shapes of the product to investigate the causes of Springback. Distortion deformation due to the bead in the center of the product was confirmed to be a large factor. A Springback reduction method of correcting uneven thickness in the product sides, a Springback reduction method of removing the bead, and a correction method of restriking after the final forming were used in a forming analysis to determine the degree of Springback reduction. For the forming method to correct uneven thickness in the sides, deformation was reduced by 12% in the upper side compared to the existing model, but deformation in the inner side increased by 1%. For the restriking forming method, deformation decreased by 25% in the upper side and 13% in the inner side. For the bead removal method, deformation decreased by 28% in the upper side and 13% in the inner side, the largest Springback correction results. This indicates that the bead has a large affect on Springback.

• 박물관보존과학
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• 제24권
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• pp.1-16
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• 2020

대구 달성 고분군 중 하나인 55호분에서 발견된 부장품 중 삼엽문이자태도의 재보존처리와 제작 기법에 관한 연구이다. 이자태도는 모도가 2점, 자도가 4점이 부착된 이합도이고 출토된 완형으로는 유일하다. 과거 2회의 보존처리가 실시된 기록이 있으며 이번에 균열부 보강제 교체를 위한 재보존처리와 함께 컴퓨터 단층촬영(CT), XRF분석, 실체현미경 관찰을 통해 유물의 재질, 성분, 제작 기법을 조사하였다. 주성분은 구리(Cu)이고 금색 부분에서는 금(Au)과 수은(Hg)이 함께 검출된 것으로 보아 구리에 수은 아말감 금도금을 한 금동으로 추정된다. 제작 기법을 조사한 결과 둥근 삼엽문의 환두부와 병부의 연결은 슴베 부분을 만들어 끼웠고 병판만 금속판으로 제작되어 있는 것을 보아 장식으로서의 기능이 높다고 판단할 수 있다. 상부 자도의 결합 방식은 모도와 같고, 하부 자도는 하나의 금속판을 재단하여 만들었다. 검초는 총 2개의 판을 재단하여 만들었고 상부 자도를 검초에 고정하기 위해 자도 도신부의 아래쪽에 지지대를 넣었으며 하부 자도는 검초 일부를 재단하여 안으로 꽂아 넣었다. 표현된 문양은, 환두부는 삼엽문, 병판은 횡주 연호문, 초구금구와 초미금구는 파상형 점열문, 어미형 초미금구는 점열문을 시문하여 제작되었다.

• 한국농공학회지
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• 제16권1호
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• pp.3263-3291
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• 1974

Experimental work of grain bin was carried out to develop the methods of natural air in-bin drying and storage. The method is considered to be more economical, labour saving, and an effective countermeasure to grain loss. To examine the possibility of farm use of the grain bin and to analyze the related factors concerned with in-bin grain drying and storage, ambient air conditions (especially the change of air temperature and relative humidity) and grain quality during drying and storage periods were investigated. A laboratory model bin was constructed to investigate the effect of different forced air conditions on the drying characteristics of rice. In addition, a grain bin with 2.2m diameter and 1.8m height, considered to be the optimum size for the average Korean farm, was constructed and tested to examine the drying and storing characteristics of rice. The weather data analyzed in this study was the nine-year (from 1964 to 1972) record of air temperature and relative humidity in the Suweon area, and the thirty-year (from 1931 to 1960) record of pentad normal relative humidity and air temperature in the Seoul area. From the results of the weather data analyses, the adequate air delivery hours (which was arbitrary defined as the condition to give less than 75% relative humidity) to dry the rice during October were about nine hours (from approximately 10 A.M. to 7 P.M, ) a day, in which the average air temperature was about 15.9$^{\circ}C$ and average relative humidity was 66%. The occurence of days having three hours of such conditions was 1, 2, and 1-day within the 1st, 2nd add last 10-day periods for the month of October, respectively. Therefore, it may be considered that the weather condition in October was satisfactory for the forced natural air drying. The results of the laboratory model bin test were analyzed to obtain the drying curve and drying rate for different drying stages and grain layers in the bin corresponding to various conditions of forced natural air. A drying experiment with a prototype grain bin showed that an approximate 5 percent grain moisture gradient through a 1.6 meter grain deposit was observed after 80 hours of intermittent drying, giving an over dried zone in the lower grain layers and an extremely high grain moisture zone in the upper layers. This indicates that an effective measure should be taken to reduce this high moisture gradient. In order to investigate the drying characteristics of bulk grain in a layerturning operation a grain bin test was performed. This showed a significant improvement of uniform drying. In this test, approximate 107 hours were required to dry a depth of 1.6 meter of grain from an initial moisture content of 22.2 percent to a moisture content of 16.7 percent using an air delivery rate of 2.8 cubic meter per a minute per every cubic meter of grain. This resulted in a 2 percent moisture gradient from the top to the bottom of the bin. During storage period, till the end of June the average temperature of grain was 2~3$^{\circ}C$ higher than ambient air temperature. But during July when the grain moisture content went up slightly (less than 1 percent), the average temperature of the grain also increased to 3~5$^{\circ}C$ higher than ambient air temperature. It is therefore recommended that for safe grain storage, grain should not be stored in sheet metal bins after mid May. From the above results, in-bin rice drying and storage can be used effectively on Korean farms. It is strongly recommended that the use of grain-bin system should be implemented for farm use to improve farm drying and storage of rice.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.239-240
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• 2008

As semiconductor devices are scaled down for better performance and more functionality, the Cu-based interconnects suffer from the increase of the resistivity of the Cu wires. The resistivity increase, which is attributed to the electron scattering from grain boundaries and interfaces, needs to be addressed in order to further scale down semiconductor devices [1]. The increase in the resistivity of the interconnect can be alleviated by increasing the grain size of electroplating (EP)-Cu or by modifying the Cu surface [1]. Another possible solution is to maximize the portion of the EP-Cu volume in the vias or damascene structures with the conformal diffusion barrier and seed layer by optimizing their deposition processes during Cu interconnect fabrication, which are currently ionized physical vapor deposition (IPVD)-based Ta/TaN bilayer and IPVD-Cu, respectively. The use of in-situ etching, during IPVD of the barrier or the seed layer, has been effective in enlarging the trench volume where the Cu is filled, resulting in improved reliability and performance of the Cu-based interconnect. However, the application of IPVD technology is expected to be limited eventually because of poor sidewall step coverage and the narrow top part of the damascene structures. Recently, Ru has been suggested as a diffusion barrier that is compatible with the direct plating of Cu [2-3]. A single-layer diffusion barrier for the direct plating of Cu is desirable to optimize the resistance of the Cu interconnects because it eliminates the Cu-seed layer. However, previous studies have shown that the Ru by itself is not a suitable diffusion barrier for Cu metallization [4-6]. Thus, the diffusion barrier performance of the Ru film should be improved in order for it to be successfully incorporated as a seed layer/barrier layer for the direct plating of Cu. The improvement of its barrier performance, by modifying the Ru microstructure from columnar to amorphous (by incorporating the N into Ru during PVD), has been previously reported [7]. Another approach for improving the barrier performance of the Ru film is to use Ru as a just seed layer and combine it with superior materials to function as a diffusion barrier against the Cu. A RulTaN bilayer prepared by PVD has recently been suggested as a seed layer/diffusion barrier for Cu. This bilayer was stable between the Cu and Si after annealing at $700^{\circ}C$ for I min [8]. Although these reports dealt with the possible applications of Ru for Cu metallization, cases where the Ru film was prepared by atomic layer deposition (ALD) have not been identified. These are important because of ALD's excellent conformality. In this study, a bilayer diffusion barrier of Ru/TaCN prepared by ALD was investigated. As the addition of the third element into the transition metal nitride disrupts the crystal lattice and leads to the formation of a stable ternary amorphous material, as indicated by Nicolet [9], ALD-TaCN is expected to improve the diffusion barrier performance of the ALD-Ru against Cu. Ru was deposited by a sequential supply of bis(ethylcyclopentadienyl)ruthenium [Ru$(EtCp)_2$] and $NH_3$plasma and TaCN by a sequential supply of $(NEt_2)_3Ta=Nbu^t$ (tert-butylimido-trisdiethylamido-tantalum, TBTDET) and $H_2$ plasma. Sheet resistance measurements, X-ray diffractometry (XRD), and Auger electron spectroscopy (AES) analysis showed that the bilayer diffusion barriers of ALD-Ru (12 nm)/ALD-TaCN (2 nm) and ALD-Ru (4nm)/ALD-TaCN (2 nm) prevented the Cu diffusion up to annealing temperatures of 600 and $550^{\circ}C$ for 30 min, respectively. This is found to be due to the excellent diffusion barrier performance of the ALD-TaCN film against the Cu, due to it having an amorphous structure. A 5-nm-thick ALD-TaCN film was even stable up to annealing at $650^{\circ}C$ between Cu and Si. Transmission electron microscopy (TEM) investigation combined with energy dispersive spectroscopy (EDS) analysis revealed that the ALD-Ru/ALD-TaCN diffusion barrier failed by the Cu diffusion through the bilayer into the Si substrate. This is due to the ALD-TaCN interlayer preventing the interfacial reaction between the Ru and Si.

• Journal of Radiation Protection and Research
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• 제10권2호
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• pp.96-108
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• 1985

감마선분광분석 및 열형광선량측정법에 의한 자연환경방사선의 선량해석에 관한 연구를 1984년 10월부터 약 1년간에 걸쳐 충남대학교 대덕캠퍼스내의 1만 $m^2$ 규모의 평면개활지에서 수행하였다. 이 연구에서 사용한 검출기는 3'${\phi}{\times}$3' NaI(T1) 섬광계수기(閃光計數器)와 plastic 에 밀봉하여 금속판에 압착 처리한 chip 과 Teflon-disk 로된 2종의 LiF TLD 였다. 실측실험으로는 3회에 걸친 24시간 cycle의 in-situ spectrometry 와 2회의 3개월 cycle 과 1회의 1개월 cycle에 걸친 TLD field dosimetry를 수행하였다. 측정한 모든 spectrum은 G(E)연산자법에 의하여 조사선량율(照射線量率)로 환산하였고 그 결과로부터 환경 방사선의 지설성분(地設成分)을 산출하였다. 결과(結果)에 의하면 spectrometry로 구한 조사선량율이 평균 $(10.54{\pm}2.96){\mu}R/hr$, TLD chip으로 측정해석한 값은 $(12.0{\pm}3.4){\mu}R/hr$, disk에서 얻은 값이 $(11.0{\pm}3.6){\mu}R/hr$로 오차범위 안에서 매우 좋은 일치를 보이고 있다. 그러나 감마선분광분석에 의한 자연방사선의 일변화(日變化)에는 가끔 심한동요가 관측되었다. 정확한 환경방사선량해석을 위하여 감마선분광분석과 TLD의 적절한 동시 배합사용이 바람직 하며, 보다 고감도의 TLD에 관한 연구와 국제비교등을 통한 선량평가의 정도향상(精度向上)을 위한 보다 깊이 있는 연구가 필요하다는 결론(結論)에 도달하였다.