• 자원리싸이클링
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• 제10권6호
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• pp.35-42
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• 2001

Air table을 이용해서, 입상플라스틱 혼합물로부터 PVC를 제거 분리하는 연구를 행하였다. Air table상에서 플라스틱이 어떠한 운동을 하는가 연구하고, PVC 10%와 PE 90%의 인공흔합물을 가지고 선별 분리시험을 행하였다. 이 연구로부터 선별 최적조건은, 9.2 Hz의 Frequency, 1.05 m/sec의 바람속도, 7.5 End-slope, 1 side-slope, 450 g/min의 Feeding speed 등이었다 PE-PVC 흔합물에서 99.96%의 PE를 98.9% 얻을 수 있었고, 88.7%의 PVC를 99.6% 얻을 수 있었다.

• Corrosion Science and Technology
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• 제2권3호
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• pp.109-116
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• 2003

It is well known that SSCC (sulfide stress corrosion cracking) is caused by drastic ingression of hydrogen during the service and accumulation of hydrogen near the potential crack initiation site in the material. It is important to characterize the hydrogen trapping behavior to evaluate the service performance of the high strength pipeline steels. In this study. the relationship between the hydrogen trapping behavior and SSCC susceptibility is evaluated in terms of alloy composition, microstructure and carbide behavior. The hydrogen trapping behavior was measured by electrochemical hydrogen permeation test cell (Devanathan cell). The SSCC susceptibility is evaluated by constant extension rate test and constant strain lest method. The hydrogen trapping behavior is affected greatly by microstructure and nature of carbide particles. The fine TiC, and NbC in the matrix of ferritic structure acts as strong irreversible trap sites whereas the bainitic structure acts as reversible trap site. The SSCC susceptibility is closely related to not only the hydrogen trapping behavior but also the loading condition. As the activity of reversible trap site increases, SSCC susceptibility decreases under static loading condition below yield strength, whereas SSCC susceptibility increases under dynamic loading condition or above yield strength. As the activity of irreversible trap site increases. SSCC susceptibility increases regardless of loading condition. It is cased by the mixed effect of dislocation on hydrogen diffusion and trapping behavior.

• 대한금속재료학회지
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• 제56권11호
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• pp.796-804
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• 2018

The Charpy impact toughness of the heat affected zone (HAZ) of electro gas welded 390 MPa yield strength grade steel, manufactured by a thermo mechanically controlled process, was investigated. The effects of added Nb on the toughness of the steel and the factors influencing scatter in toughness are discussed in the present work. It was observed that adding Nb to the steel led to the deterioration of HAZ toughness. The presence of soluble Nb in the HAZ increased its hardenability and resulted in a larger amount of low toughness bainitic microstructure. Microstructural observations in the notch root area revealed the significant role of different microstructures in the area. In the presence of a larger amount of bainitic microstructures, the HAZ exhibited a lower Charpy toughness with a larger scatter in toughness. A softened zone with a lower hardness than the base metal was formed in the HAZ. However, theoretical analysis revealed that the presence of the zone might not be a problem in a real welded joint because of the plastic restraint effect enforced by surrounding materials.

• 소성∙가공
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• 제30권2호
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• pp.91-98
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• 2021

The present study deals with the microstructure and mechanical properties of 700 MPa-grade high-strength seismic resistant reinforced steel bars fabricated by various TempCore process conditions. For the steel bars, in the surface region tempered martensite was formed by water cooling and subsequent self-tempering during TempCore process, while in the center region there was ferrite-pearlite or bainite microstructure. The steel bar fabricated by the highest water flow and the lowest equalizing temperature had the highest hardness in all regions due to the relatively fine microstructure of tempered martensite and bainite. In addition, the steel bar having finer microstructures as well as the high fraction of tempered martensite in the surface region showed the highest yield and tensile strengths. The presence of vanadium precipitates and the high fraction of ferrite contributed to the improvement of seismic resistance such as high tensile-to-yield strength ratio and high uniform elongation.

• 한국연초학회지
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• 제11권1호
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• pp.49-64
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• 1989

The study was carried out to investigate the effect of control leaf number on growth and chemical characteristics, and on yield and quality In (rue-cured tobacco The rest upper leaves of 14, 16, and 18 leaves per plant were removed at button stage, and the plants were harvested :0, 12, and 16 leaves with discard 4 leaves of the bottom, respectively. 1. There were showed a tendency to increase in length (LL), width (LW), area (LA), fresh (LFW) and dry weight (LDW) per leaf as leaf numbers were decreased, while those per plant and the ratios of increase of those per plant were decreased. 2. In compensation effect (CE), there were increase in LL, LFW, LDW, LL/LW and LDW/LFW with each decreased in leaf numbers while LW was decreased, LA unchanged. 3. There were significant Increases in LL, LW, and LA at 5th~8th stalk positions form bottom (SP), while those .at 13th~16th SF were decreased. Also, LDW at 5th~l0th, and LDW/LFW and weight Per unit leaf area at 11th 16th were Increased as leaf numbers decreased. 4. Mean per plant and CE of nicotine were increased, but those of sugar were decreased with each decrease In leaf numbers. In addition, nicotine contents at 5th~14th SP except for 9th~10th were increased, otherwise sugar contents at 7th~14th were decreased. 5. There were showed a tendency to increase in grade per Plant and in tirade at 5th~8th SP, but decrease in CE of grade as leaf numbers were decreased. There wee significant decrease in grade at 11th~14th SP. Also, ratio of 5 grade was decreased, while ratios of 3 and 4 grades were increased. 6. When the 2 leaves at 3rd~4th SP were harvested, price was decrease 2.6% and yield was increased 5.8 %. 7. When the 6 leaves from convention were removed at but ton stage, effects of apparent, compensational, and net per leaf on yield were -3.9%, +2.6%, and -6.5%, respectively, and those on price were +1.1%, -1.6% and +2.7%, respectively.

• Journal of the Korean Wood Science and Technology
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• 제38권2호
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• pp.85-93
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• 2010

Japanese cedar has low density and poor mechanical performance. Manufacturing glue-laminated timber (glulam) is the best way to compensate for its poor mechanical performance. The Korean Standard (KS) confines outermost lamina of glulam to higher grade than E8, but the yield of higher than grade E8 from logs is only 6.5%. Therefore, the aim of this study is to investigate the possibility of non-Korean-Standard glulam in structural applications. Allowable stresses determined by both hand-calculation and Monte-Carlo simulation show a higher allowable stress than that of the KS-standard glulam of 6S-22B. In the Korean Standard (KS), knot characteristics are not taken into account. Japanese cedar has relatively small knots. We believe that the small knots in Japanese cedar contribute to a higher allowable stress than the KS-standard glulam would predict. The species classification of KS is required to be further subdivided into sub-species groups based on knot characteristics.

• 한국초지조사료학회지
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• 제12권4호
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• pp.246-252
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• 1992

In order to reduce the problems from overlapping between rye harvest and maize seeding dates, and also to improve the growth, productivity and nutritive value of rye (Secale cereale L.), an experiment was carried out to determine the variety effect of rye on the forage production system, and seeding date effect on the yield and quality of rye. The experiment was conducted in the forage testing field of S.N.U., Suweon, from September 1988 to May 1989. The dry matter and in vitro digestible dry matter yields of rye harvested 14 April were 5.2 t and 4.6 t/ha with an early maturing rye variety, Winter more, but 3.1 t and 2.8 t/ha were obtained with a late maturing rye variety, Kodiak. When seeding date was delayed, a significant decrease in dry matter yield was observed. ADF and NDF contents, and IVDMD of an early maturing rye, Winter more, harvested 14 April were 25.6, 44.8 and 81.9 %, but those of a late maturing rye, Kodiak, were 21.1, 39.5 and 88.9 %, respectively. ADF and NDF contents of rye were increased as the seeding date was delayed, but ail forage ryes from different seeding dates as well as varieties were recorded as the 1st grade proposed by market hay grades. The dry matter and in vitro digestible dry matter yields of rye harvested at 80 %heading stage were significantly decreased as delayed seeding date, but no significant differences were found between early and late maturing varieties. No differences in ADF and NDF contents, and IVDMD of the rye harvested at 80% heading stage were found among the treatments, but all forage ryes were evaluated as the 4 th grade proposed by market hay grades.

• Asian-Australasian Journal of Animal Sciences
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• 제28권11호
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• pp.1592-1598
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• 2015

This study was conducted to determine the effects of feeding a trace minerals-fortified microbial culture (TMC) on the performance and carcass characteristics of late-fattening Hanwoo steers. A mixture of microbes (0.6% [v/w] of Enterobacter sp., Bacillus sp., Lactobacillus sp., and Saccharomyces sp.) was cultured with 99% feedstuff for ensiling and 0.4% trace minerals (zinc, selenium, copper, and cobalt). Sixteen late-fattening steers (mean age, 21.8 months) were allocated to two diets: a control diet (concentrate mix and rice straw) and a treated diet (control diet+3.3% TMC). At a mean age of 31.1 months, all the steers were slaughtered. The addition of TMC to the diet did not affect the average daily weight gain of the late fattening steers, compared with that of control steers. Moreover, consuming the TMC-supplemented diet did not affect cold carcass weight, yield traits such as back fat thickness, longissimus muscle area, yield index or yield grade, or quality traits such as meat color, fat color, texture, maturity, marbling score, or quality grade. However, consumption of a TMC-supplemented diet increased the concentrations of zinc, selenium, and sulfur (p<0.05) in the longissimus muscle. With respect to amino acids, animals consuming TMC showed increased (p<0.05) concentrations of lysine, leucine, and valine among essential amino acids and a decreased (p<0.05) concentration of proline among non-essential amino acids. In conclusion, the consumption of a TMC-supplemented diet during the late-fattening period elevated the concentrations of certain trace minerals and essential amino acids in the longissimus muscle, without any deleterious effects on performance and other carcass characteristics of Hanwoo steers.

• 한국초지조사료학회지
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• 제32권4호
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• pp.387-396
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• 2012

A study was conducted to determine the dietary effects of Na-bentonite (NaB) and probiotics on meat characteristics and health of Hanwoo steers fed rice straw as a sole roughage source. A total of 24 growing Hanwoo steers (avg BW 232 kg) were assigned to two treatments which included a control diet (concentrate mix and rice straw) and a treatment diet (control diet + 0.5-1.0% NaB + 0.5-1.0% probiotics. The diets were fed for 22 months up to the time the animals were slaughtered. Dietary treatment increased (p<0.05) concentrations of trace minerals such as Zn, Cu, and Fe in the longissimus muscle compared to the control. The treatment diet did not affect cold carcass weight, yield traits such as backfat thickness, longissimus muscle area, yield index, yield grade and quality traits such as marbling score, meat color, fat color, texture, maturity and quality grade. Blood profiles of growing steers were within the normal ranges for healthy cattle. In conclusion, feeding a combination of clay mineral and probiotics to Hanwoo steers fed rice straw as a sole roughage source could have a desirable effect on improving trace mineral retention in longissimus muscle without any deleterious effects on carcass traits of steers.

• 한국축산식품학회지
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• 제31권2호
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• pp.280-289
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• 2011

본 연구는 2009년도에 전국에서 출하된 한우 암소 및 거세우 69,159두를 대상으로 등지방두께가 도체등급요인 및 경락가격에 미치는 영향을 구명하였다. 평균 등지방두께는 거세우(12.57 mm)가 암소(11.93 mm) 보다 높았으며, 암소의 77.52%가 등지방두께 4-15 mm 구간에, 거세우의 85.91 %가 등지방두께 4-18 mm 구간에 속하였다. 암소 및 거세우의 도체중(평균, 315.5 kg과 413.2 kg)과 배최장근면적(평균, 76.73 $cm^2$와 86.23 $cm^2$)은 등지방두께가 높아짐에 따라 증가 하였으며(p<0.05), 육량등급은 C등급으로 낮아졌다(p<0.05). 평균 근내지방도는 거세우(5.29)가 암소(3.83)보다 우수하였으며 등지방두께 21 mm까지 증가하였고(p<0.05), 22 mm 이상부터 감소하였다. 암소 및 거세우의 평균 성숙도는 각각 6.11과 2.12로 암소의 골화 정도가 높았으며 평균 육색은 4.85 및 4.67 로써 비슷한 수준이었다. 암소의 평균 육질등급은 1등급과 2등급의 중간 수준(평균 3.55)이었고 거세우는 1등급과 $1^+$등급의 중간 수준(평균 2.58)으로 등지방두께가 21 mm까지 육질등급은 향상되었으나(p<0.05), 22 mm 이상부터 암소는 2등급 수준으로 거세우는 1등급 수준으로 낮아졌다. 암소도체 kg당 경락가격은 등지방두께 13-15 mm 구간에서 14,970원으로, 거세우는 등지방두께 10-12 mm 구간에서 17,318원으로 가장 높았다(p<0.05). 도체 kg당 경락가격은 암소는 등지방두께 18 mm이상, 거세우는 15 mm이상에서 유의적으로(p<0.05) 감소되었다. 특히, 거세우의 경우 도체 경락가격은 등지방 두께 15 mm 이상에서 유의적인 차이가 없었다. $1^{++}$등급 출현율은 암소는 등지방두께 19-21 mm 구간에서 7.33%, 거세우는 22-24 mm구간에서 25.04%로 가장 높았다. 육량 A등급은 등지방두께 4-6 mm구간에서 암소 및 거세우 각각 55.67%와 93.33%로 가장 높았다. 암소 및 거세우의 등지방 두께는 육량지수와 각각 $-0.97^{**}$ 및 $-0.96^{**}$로써 상관관계가 높았으며 근내지방도와 각각 $0.20^{**}$ 및 $0.14^{**}$ 상관관계가 있었고 육질 등급($1^{++}$등급 = 1, 3등급 = 5)과의 상관관계는 $-0.15^{**}$로 같았다. 본 연구에서 한우도체의 등지방두께는 도체등급 요인 및 도체가격에 영향을 미치는 것으로 분석되어 금후 한우도체의 등지방 감소를 위한 다양한 연구가 필요하다고 사료된다.