• KOREAN JOURNAL OF CROP SCIENCE
• /
• v.49 no.4
• /
• pp.271-278
• /
• 2004

This study was conducted to obtain basic information of growth, chlorophyll, and $Na^+\;and\;K^+$ content of rice (Oryza sativa L.) seedlings after transplanting in different NaCl conditions. Plants grown in pots for 8 days after germination were grown for 10 days after transplanting in 50 and 100 mM NaCl concentrations. At higher NaCl concentration, plant height, root length, dry weight and chlorophyll content were reduced with NaCl stress. Among rice cultivars, the shoot dry weight of Gancheokbyeo, Janganbyeo and Hwasungbyeo, and the root dry weight of Janganbyeo, Gancheokbyeo and Juanbyeo showed relatively low reduction compared to the other rice cultivars at 100 mM NaCl stress. The $Na^+$ content in seedling rapidly increased with the increase of NaCl concentration but $K^+$ contents decreased. There was a significant relationship between $Na^+$ content and shoot and root dry weight after transplanting rice seedlings to saline conditions. The shoot and root dry weight showed highly negative relationship with the $Na^+/K^+$ ratio in saline conditions.

• Transactions of Materials Processing
• /
• v.4 no.2
• /
• pp.141-150
• /
• 1995

The purpose of the open die press forging is to maximize the internal deformation for better structural homogeneity and center-line consolidation in case of the ingot. A two and three dimensional viscoplastic finite element analysis is carried out for the plate, cylinder and square forging with the flat die in order to study the forging effects during the process. Effect of width, height reduction, and die staggering are studied through simulation of the process. Thus favorable working conditions are suggested for better and more disirable product quality.

• Proceedings of the KSR Conference
• /
• 2007.05a
• /
• pp.1782-1788
• /
• 2007

This study analyzed ground settlement and ground stress depending on tunnel excavation and the ground reinforcing grouting methods for double line road tunnel through deep weathered zone. Diameter of double line road tunnel was approximately 12m and umbrella arch method and side wall reinforcing grouting were applied. The ring-cut split excavation method and CD-cut excavation method for excavation method were applied. Analysis of failure rate and vertical stress ratio show that the tunnel for which the height of the cover(H) was higher than four times the diameter, it can be considered a deep tunnel. Comparisons of various excavation and ground reinforcement methods were showed that CD-cut method results in lower surface and crown settlement, and lower failure rate than where using Ring-cut split method. In addition the side wall reinforcing grouting resulted in reduction of tunnel displacement and settlement.

• Korean Journal of Poultry Science
• /
• v.45 no.3
• /
• pp.147-154
• /
• 2018

A total of 90 one-day-old male broilers (Ross 308) were randomly assigned to one of the three dietary treatments, each consisting of six replicates (5 broilers/cage). The dietary treatments were 1) control (CON: fresh clean water with no supplement); 2) low dose [LD: CON + 1.56% extractions from the wooden chips (EWC)] and 3) high dose (HD: CON + 12.5% EWC). Drinking water supplemented with EWC was provided using specifically designed individual nipple drinker units. Average daily water intake (ADWI), average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) were measured weekly for 21 days. One broiler from each cage was euthanized for measuring the visceral organ weights and collecting ileal tissue samples for ileal architecture analysis on day 21. Broilers assigned to the LD and HD watery groups showed higher ADWI than that in broilers consumed CON on day 7 (P<0.05). The broilers subjected to HD treatment showed a deeper crypt depth (P<0.05) than that in broilers subjected to LD and CON on day 21. Therefore, broilers consumed HD showed a lower (P<0.05) villus height:crypt depth ratio than that broilers consumed CON on day 21. Broilers provided drinking water containing any of the tested concentrations of EWC showed no effect (P > 0.05) on growth performance, ileal villus height, and visceral organ weights as compared with those in the CON from hatch to 21 days. In conclusion, broilers fed HD showed reduction in villus height:crypt depth ratio without impairing growth performance and visceral organ weights for the experimental period.

• Transactions of Materials Processing
• /
• v.30 no.4
• /
• pp.195-200
• /
• 2021

In this study, we investigated the dominant processing variables that would influence the microstructural development of AA6061 deformed by differential speed rolling (DSR) at ambient temperature. For this purpose, we carried out a series of DSR on the samples to investigate the effects of roll speed ratio, sample rotation, and number of operation under specific rotation. Among these, the condition with a height reduction of 75% at a speed ratio of 1:4 through rotation along rolling direction (RR) displayed the pronounced results of more homogenous matrix-structure and superior mechanical properties than the others tested in this study. This was mainly due to the cross shearing of macro-shear pattern in segment where dynamic recrystallization took place with ease throughout the sample. Thus, an average microhardness value of 101 Hv was obtained in the present sample deformed by 4-pass DSR with RR where macro cross-shearing was effectively applied.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2008.03a
• /
• pp.229-241
• /
• 2008

In order to investigate stabilization effect on As-contaminated soils treated by zero-valent iron(ZVI) and industrial by-products, batch tests and column tests were carried out with As-contaminated soils collected from farmland around the abandoned mine site. In batch tests, ZVI and industrial by-products(blast furnace slag, steel refining slag and oyster shell powder) were used as treatment materials to reduce As. Industrial by-products were mixed with As-contaminated soils, in the ratio of 1%, 3%, 5% and 7% on the weight base of dried soil. After incubation, all samples showed the reduction of As concentration and it was expected that ZVI and steel refining slag were effective treatment materials to remove As among treatment materials used in batch test. In column tests, columns were made by acrylic with the dimension of diameter=10cm, height=100cm, thickness=1cm and these columns were filled with untreated soils and treated soils mixed with ZVI and steel refining slag(mixing ratio=3%). Distilled water was discharged into the columns with the velocity of 1 pore-volume/day. During test, pH, EC, Eh and As concentration were measured in the regular term(1 pore-volume). As a result, ZVI and steel refining slag were shown 93%, 62% reduction of As concentration respectively by comparison with untreated soils. Therefore, if ZVI and steel refining slag are used as treatment materials in As-contaminated soils, it is expected that the As concentration in soils is reduced effectively.

• Nuclear Engineering and Technology
• /
• v.37 no.5
• /
• pp.479-490
• /
• 2005

The thermalhydraulic performance of a CANDU-6 reactor loaded with various CANFLEX fuel bundles is evaluated by the NUCIRC code, which is incorporated with recent models of pressure drop and critical heat flux (CHF) predictions based on high-pressure steam-water tests for the CANFLEX bundle as well as a 37-element bundle. The distributions of channel flow rate, channel exit quality, critical channel power (CCP), and critical power ratio (CPR) for the CANFLEX bundles (with natural or recycled uranium fuel) in the CANDU-6 reactor fuel channel are calculated by the code. The effects of axial and radial heat flux on CCP are evaluated by assuming that the recycled uranium fuel (CANFLEX-RU) has the same geometric data as the natural uranium fuel bundle (CANFLEX-NU), but a different power distribution due to different fuel composition and refueling scheme. In addition, the effects of pressure tube creep and bearing-pad height are examined by comparing various results of uncrept, and $3.3\%\;and\;5.1\%$ crept channels loaded with CANFLEX bundles with 1.4 mm or 1.7 mm high bearing-pads with those of the 37-element bundle. The distributions of the channel flow rate and CCP for the CANFLEX-NU or -RU bundle show a typical trend for a CANDU-6 reactor channel, and the CPRs are maintained above at least 1.444 (NU) or 1.455 (RU) in the uncrept channel. The enhanced CHF of the CANFLEX bundle (particularly with 1.7mm height bearing-pads) produces a higher thermal margin and considerably less sensitivity to CCP reduction due to the pressure tube creep than the 37-element bundle. The CCP enhancement due to the raised bearing-pads is estimated to be about $3\%\~5\%$ for the CANFLEX-NU and $2\%\~6\%$ for the CANFLEX-RU bundle, respectively.

• Transactions of Materials Processing
• /
• v.30 no.6
• /
• pp.291-300
• /
• 2021

Currently, starting with electric vehicles, the application of ultra-high-strength steel sheets and light metals has expanded to improve mileage by reducing vehicle weight. At a time when internal combustion engine vehicles are rapidly changing to electric vehicles, the application of ultra-high-strength steel is expanding to satisfy both weight reductions and the performance safety of the chassis parts. There is an urgent need to improve the quality of parts without defects. It is particularly difficult to estimate the part formability through the finite element method (FEM) in the burring operation, so product design has been based on the hole expansion ratio (HER) and experience. In this study, design of experiment (DOE), analysis of variance (ANOVA), and regression analysis were combined to optimize the formability by adjusting the process variables affecting the burring formability of ultra-high-strength steel parts. The optimal variables were derived by analyzing the influence of variables and the correlation between the variables through FE analysis. Finally, the optimized process parameters were verified by comparing experiment with simulation. As for the main influence of each process variable, the initial hole diameter of the piercing process and the shape height of the preforming process had the greatest effects on burring formability, while the effect of a lower round of punching in the burring process was the least. Moreover, as the diameter of the initial hole increased, the thickness reduction rate in the burring part decreased, and the final burring height increased as the shape height during preforming increased.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.18 no.3
• /
• pp.320-326
• /
• 2017

Multistage deep-drawing technology is used widely in the production of mobile phone battery cases to improve productivity and economy. To ensure adequate capacity and rigidity, such cases are fabricated as a rectangular cup with a high slender ratio. The multistage deep-drawing of a rectangular cup entails a high slender ratio, and the heights of the product sides may be non-uniform because of the complicated deformation mechanisms. This causes problems in product assembly that affects the surface quality of the case. This study examined a blank shape that minimizes the height variations of the product to resolve the aforementioned problems. Optimization design and analysis were performed to identify the shape that yields the least variation. The long and short sides of an oval blank were set as the design variables. The objective function was set to yield the lowest height difference, and the thickness reduction rate of the product was set to the target range. In addition, the height of the final shape was set as a constraint. The height difference was minimized successfully using the optimized design. The design process of the initial blank for all rectangular shapes can be automated in the future.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.3
• /
• pp.186-195
• /
• 2010

This study has attempted to suggest a proper reinforcement method by strengthening unbonded post -tensioning through height of an anchorage hole, form of a saddle, and loading time point as parameters and evaluating the reinforcement method through a bending experiment. The result of this experiment indicated effects of reinforcement since the maximum strength ratio(the ratio of an experimental value to theoretical value) of SC composite beams before prestressed was 0.97 and after prestress were 1.00~1.21. As a result of analysis on displacement and strain, irrespective of height of an anchorage hole and loading time point, the D120-series specimen where an anchorage hole was installed on the neutral axis after reinforcement showed that its deflection continuously increased without sudden load reduction after maximum load and it stably behaved with relatively low strain of each part. In terms of reinforcement effects, the maximum strength of SCR-UD120 specimen prestressed after pre-loading was increased 1.72 times comparing to SC composite beams so SCR-UD120 specimen prestressed after pre-loading was shown to be the best.