• 한국기계가공학회지
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• 제21권7호
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• pp.98-104
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• 2022

Circular sawing and milling are general machining processes used for routing fiber-reinforced plastics (FRP). In this study, the productivity and cutting quality of a circular saw and flat endmill were compared. As a result, the productivity of the circular saw was approximately ten times higher than that of the endmill for the same tool life, and the burr size of the circular saw was 14 times smaller than that of the flat-end mill. The spectrogram analysis of the cutting sound also showed that the acoustic emission of the circular saw was more uniform than that of the flat end mill. Circular sawing is thus a more suitable process for the straight cutting of pultrusion FRP than a flat endmill.

• 한국정밀공학회지
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• 제13권3호
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• pp.49-55
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• 1996

Recently, the necessity for more accurate automatic gauge control has increased of customers' requirement for cold rolled steel sheets with thinner gauge and better gauge quality. Therefore, many cold rolling mills replaced its electric screw down automatic gauge control system with a new hydraulic automatic gauge control system, to ensure closer gauge tolerance. In this paper, The performance of a hydraulic automatic gauge control system for cold rolling has been investigated under industrial conditions. It was investigated that variation of gauge deviation according to the final products thickness, cold rolling speed and pass number, in the actual rolling mill. As a result, it was found that the system enables strip thickness variation to be reduced substantially and caused by poor gauge deviation have been drastically decreased. The test results are as following. The more the exit steel strip thickness is thick, the smaller the aguge deviation rate is large, and the more it is thin, the large the gauge deviation rate is large. Because the gauge deviation is larger at accleration speed and deceleration speed than steady speed, so automatic gauge control system is better to adopt over 50m/min. automatic gauge control system reduces rapidly large thickness deviation.

• 펄프종이기술
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• 제38권2호
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• pp.9-15
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• 2006

Neutral sizing is required for linerboard to solve the troubles in strength and process caused by recycled raw materials. AKD sizing efficiency can be influenced by process condition like white water quality, fines retention and so on. Therefore, this study was aimed to evaluate sizing performance of general and fast cure type AKDs using process water obtained from linerboard mill. To evaluate effect of process water quality on AKD sizing, white water was diluted with tap water at the different dilution ratios and UKP slurry was sized using the prepared water. Also, effects of inorganic and organic ion material on sizing were examined. When white water was used for stock forming, UKP sheet showed very low sizing degree. Sizing degree of sheet was increased with increase of dilution ratio because water quality was improved. Especially anionic organic material had a greater influence on AKD sizing than inorganic material. When white water quality was deteriorated, fast cure type AKD showed superior sizing performance to general type AKD.

• 한국환경보건학회지
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• 제35권5호
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• pp.411-416
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• 2009

This study was initiated to improve the cooling water quality by chemical coagulation and sedimentation in steel mills. Due to the inefficient flocculation in the settling tanks of blast furnace cooling water systems, the solid particles in the cooling water overflow accumulate and clog the cooling system. To protect the cooling water system from such fouling, proper flocculants must be continuously used. Laboratory tests were performed for the indirect cooling water system of a plate mill. The batch test in the gas scrubbing cooling water system of a blast furnace showed that the proposed coagulant was more effective for the improvement of coagulation and sedimentation than the existing one. During the tests, cationic flocculants were more effective than use of only an anionic flocculant. The suggested combination of anionic and cationic flocculants can probably improve the turbidity removal efficiency of the cooling water. Proper control of the overflow rate by the designed residence time would help turbidity removal efficiency in the settling tank. In addition, the settling can be enhanced by adopting rapid and slow mixing alternatively. Scale problems in blast furnace cooling water system were reduced to some extent by efficient settling.

• 한국식품저장유통학회지
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• 제14권6호
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• pp.578-583
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• 2007

고 이산화탄소 전처리가 토마토의 숙성 중 품질 변화에 미치는 영향을 구명하기 위해 breaker와 pink 단계에 토마토를 수확한 후 고 이산화탄소(25, 50 및 100%)를 24시간 처리한 후 상온에서 숙성시키면서 품질변화를 조사하였다. 이산화탄소 전처리시 숙성기간 중 과피 변색과 과실의 연화가 억제되는 효과가 극명하였으며 이러한 효과는 pink 단계의 토마토 보다는 breaker 단계의 토마토에서 더 컸다. 이산화탄소 처리가 토마토의 숙성 중 당도에 미치는 영향은 없었으며, 100% 농도 처리시 breaker 토마토의 산도가 낮아지는 경향을 보였다. 관능검사를 실시한 결과 breaker 토마토의 경우 고 이산화탄소 처리에 의해 단맛이 감소하였다. 토마토의 산미와 조직감은 과실의 숙도에 관계없이 이산화탄소 처리에 의해 높게 유지되었다. Breaker 단계에서 수확한 토마토는 이산화탄소 전처리에 의한 이취 발생이 없으나, pink 토마토에서는 이취가 발생하여 향에 대한 선호도가 낮아졌다. 상온에서 22일 후 고 이산화탄소 장해 증상이 관찰되었는데, breaker 토마토는 50% 이상의 농도에서, pink 토마토의 경우 25% 이상의 농도 처리시 발생하였다.

• 한국환경농학회지
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• 제9권2호
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• pp.143-151
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• 1990

배양액(培養液) 및 배지(培地)의 종류(種類)를 달리하여 수행(遂行)한 양액재배(養液栽培) 실험(實驗)에 있어서 오이(Cucumis sativus L.)와 토마토(Lycopersicon esculentum MILL)의 생육(生育)과 품질(品質)에 미치는 영향(影響)을 조사(調査)한 바 그에 대한 실험(實驗) 결과(結果)를 요약하면 다음과 같다. 1. 오이와 토마토의 생육(生育) 및 수량(收量)은 Cooper액(液)을 이용(利用)한 암선재배(岩線栽培)에서 가장 높게 나타났다. 2. 복합비료(複合肥料) 양액(養液)을 이용(利用)한 암선재배(岩線栽培) 시(時) 생육(生育) 및 수(收量)은 sand-sack culture에서 가장 양호(良好)하였다. 3. 복합비료(複合肥料) 양액(養液)을 사용(利用)한 암선재배(岩線栽培) 시(時) 초기생육(初期生育)에는 토양재배(土壤栽培)보다는 좋았으나 후기생육(後期生育)은 점차 낮아지는 결과(結果)를 나타내었다. 4. 오이와 토마토의 과실내(果實內) vitamin C함량(含量)은 토양재배(土壤栽培)와 비교(比較) 시(時) 복합비료양액(複合肥料養液)을 사용(利用)한 암선재배구(岩線栽培區)를 제외하고 나머지 처리구(處理區)에서는 차이가 없었다. 5. 오이 및 토마토 건물중(乾物重), total-N 및 무기성분(無機成分)의 함량(含量)에서 각 처리구별(處理區別) 뚜렷한 차이는 나타나지 않았다.

• 한국약용작물학회지
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• 제26권6호
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• pp.477-481
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• 2018

Background: Recently, jujube (Zizyphus jujuba Mill.) has been attracting attention as a fruit, and its cultivation in rain shelter house is increasing to produce the high quality fresh jujube. This study was carried out to investigate the growth and fruit characteristics of jujube according to the types of rain shelter house. Methods and Results: The characteristics of 5-year-old Bokjo cultivar cultivated in 3 types of rain shelter house, multi span rain shelter house with roof vent (Type I), single span house with a column in the center and roof vent (Type II) and single span house with a column in the center and without roof vent (Type III), and open field were examined. The sprouting and blooming period were different among the types of rain shelter house. The diameter of main stem was higher in rain shelter houses than in the open field. There was no a significant difference in fruit number per leaf stem among the types of cultivation. The incidence of fruit cracking in open field cultivation which was 51.2% was much higher than that in Type I 21.6%, Type II 19.3%, and Type III 25.5%. The fruit size and weight in rain shelter houses, especially in Type III rain shelter house were higher than those in the open field and the soluble solids content of fruit in Type I and Type II was higher than in Type III rain shelter house and the open field. Conclusions: The results show that the growth and fruit quality of jujube were improved by cultivation in rain shelter house, and affected by the types of rain shelter house.

• 한국건설순환자원학회논문집
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• 제9권1호
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• pp.20-25
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• 2021

시멘트의 주 원료인 시멘트 클링커는 주원료로서 석회석을 사용하여 제조되며, 석회석의 품위에 따라 부원료의 사용이 변화되고, 시멘트 클링커의 생산에도 큰 영향을 미치게 된다. 본 연구에서는 시멘트 클링커 원료인 석회석의 CaO 함량의 변화가 Raw Mill 분쇄성과 시멘트 클링커의 소성성에 미치는 영향성을 파악하기 위하여, 석회석 CaO 함량을 변화시킨 조합원료의 분쇄시간 측정으로 분쇄성을 비교 검토하였고, 분쇄된 조합원료를 1350~1500℃의 범위에서 소성하여 소성성 지수 계산에 의한 시멘트 클링커의 소성성을 파악하였다. 석회석의 품위가 낮을수록 조합원료의 분쇄성은 저하하였고, 석회석의 CaO 함량이 낮을수록 소성온도에 따른 F-CaO의 변화가 크게 나타났다. 그에 따라 높은 B.I. 값이 계산되어, 낮은 시멘트 클링커 소성성을 나타내었다. 또한, 시멘트 클링커의 광물분석 결과에서는 소성온도의 증가로 F-CaO 값이 저하하는 경우, Belite 함량의 감소와 그에 따른 Alite 함량의 증가가 관찰되었다. Alite의 경우 석회석 CaO 함량이 증가함에 따라 R형의 비율은 감소하고 M형의 비율이 증가하였다.

• Corrosion Science and Technology
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• 제6권4호
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• pp.193-197
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• 2007

It is well known that the development of Advanced High Strength Steels (AHSS) is very important for the automotive industry in order to improve fuel efficiency and the reduction of material costs. However, it is particularly difficult to improve the surface quality of AHSS because the high amount of Si, Al, Mn and Ti etc. in AHSS promote selective oxidation, resulting in surface defects. The reheating process in the hot strip mill would cause severe oxidation because it is carried out at elevated temperatures under aggressive environments. In this study a reheating furnace simulator was developed to investigate oxidation phenomena in the reheating process. The environmental gas for the reheating furnace was made by burning coke oven gas with air in the simulator. The air/fuel ratio is precisely controlled by MFC. Ti oxides are easily formed on grain boundaries and Mn and Si oxides are usually formed in inner grains near the steel surface with a small round shape.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 춘계학술발표대회 개요집
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• pp.102-104
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• 2003

Laser weldability of aluminized steels of 0.8mm thick has been investigated. Test materials were cut from the commercial steels that were produced at the Coating Mill of POCOS. Test coupons for welding were prepared by using a conventional shearing machine and no additional edge treatment was peformed. Nd:YAG laser welding system was mainly applied to make weld specimens. Test results revealed that almost no spattering was observed even though the welding was peformed with no overlap joint clearance. Bead quality of aluminized steel laser weld was smooth and stable. According to x-ray inspection results, it was proved that the laser welds of aluminized steels were metallurgically defect free.