• Journal of the Korean Institute of Landscape Architecture
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• v.37 no.2
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• pp.36-46
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• 2009

The objective of this study is to analyze the effect of artificial soil ground on a structure. When the artificial soil ground is planted, the technical factors to be considered will be the load for buildings and the growth of plants. There are no current studies of the effect of artificial soil ground on a structure and this study will analyze the load effects of artificial soil ground, which mixes both pearlite and natural soil on structures. The load affecting the structures due to artificial soil ground will be maximized when the artificial soil ground becomes saturated, and which would occur when the rainfall intensity exceeds the infiltration capacity of the artificial soil ground. In order to determine whether the artificial soil ground has reached saturation or not, a 10 years frequency and 10 minutes rainfall intensity which is used for in urban drain design, is utilized. The hydraulic conductivity of artificial soil and mixed soil has been changed depending on the proportion of the mix, It has a range of fluctuation in the degree of hardening, in particular, but does not exceed the 10 minutes rainfall intensity over 10 years frequency in the most cases. Therefore, it would be efficient to apply the saturated unit weight of artificial soil ground as the design load of a structure.

• Journal of Bio-Environment Control
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• v.16 no.2
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• pp.142-145
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• 2007

Growth characteristics according to mixture ratio of used-rockwool in pot nursery, in Pinus densiflora, Torreya nucifera, Quercus acutissina and Fraxinus mandshurica nursery, was investigated. The used-rockwool on mixture ratio between used-rockwool and control (peatmoss: pearlite=1:1, v/v) were 0%, 30%, 50% and 70%. Flesh weight, dry weight and height of tree, in Pinus densiflora nursery, increased much more in 50% and 70% media but trunk diameter of tree had no difference according to mixture ratio. In Torreya nucifera nursery, flesh weight and height of tree in 70% medium and trunk diameter and numbers of shoot of tree in 50% and 70% media increased. Flesh weight, height and trunk diameter of tree, and chlorophyll (SPAD) and photosynthesis rate, in Quercus acutissina nursery, increased much more in 50% and 70% media, but dry weight of tree had only difference between non-mixed and mixed with rockwool. In Fraxinus mandshurica nursery, flesh weight and photosynthesis rate of tree increased much more in 70% medium, height, trunk diameter and total chlorophyll of tree had difference according to non-mixed and mixed with rockwool or had no only difference according to mixture ratio, respectively.

• Journal of Conservation Science
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• v.20
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• pp.67-80
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• 2007

Icheon Seolbong fortress is located in Saum-dong, Icheon, Gyeonggi-do Province that its date is founded as 4th century of Bakjae dynasty after excavation by Dankook university museum. Excavated artifacts show various kinds such as earthenwares, ceramics, metal artifacts and so on. Especially many iron artifacts were founded in where Bakjae earthenwares were found that it indicates iron artifacts were manufactured in Bakjae Dynasty. From 6 iron sickles, called Beollat and Millet, samples were taken to examine mircostructures and from the results used iron material, shape-forging, steel-making process, heat treatment were investigated. From this late 4th century Bakjae dynasty iron manufacture profess was established. From the result, different treatment were used in different area of the sickles according to the its use. Beollats were quenched in blade and it was used for special purpose that require Intensity. Millats did not have special treatment that it was used to cut rice plant and plant. Used material was steel, steel was previously made by certain steel-making process. It is formed to produce iron ware and the area where intensity is required heat treatment was employed to make it strong. From the investigation it is derived that iron ware manufacture process in Bakjae dynasty is steel making$\rightarrow$shape-forging$\rightarrow$and heat treatment.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.5
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• pp.252-261
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• 2017

This study examined the effect of heat treatment on the microstructure and mechanical properties of J55 line pipe steel. The experiments were carried out at under the following various conditions: austenization temperature($880^{\circ}C$, $910^{\circ}C$, $940^{\circ}C$), cooling methods(water quenching, oil quenching) and tempering temperature(none, $550^{\circ}C$, $650^{\circ}C$). The phase diagram and CCT curve were simulated based on the chemical composition of J55 steel to predict the microstructures. In the results, A1, A3 temperature decreased. As the austenization temperature increased, existing austenite grains grew exponentially which seriously degraded their mechanical properties. Various microstructures, including martensite, bainite, ferrite, and pearlite, developed in accordance with the heat treatments and were closely correlated with hardness, tensile strength and toughness. Martensite was formed after water quenching, but bainite and ferrite appeared after oil quenching. FeC precipitation formed and coarsened during tempering, which improved their toughness.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.69-76
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• 2018

This study examined the effect of the heat treatment and alloying elements (B, Ti) on the microstructures and mechanical properties of API J55 steel. The experiments were carried out using various austenization temperatures ($880^{\circ}C$, $910^{\circ}C$, $940^{\circ}C$), cooling methods (water quenching, oil quenching) and tempering temperatures (none, $550^{\circ}C$, $650^{\circ}C$) with J55 and J55+B,Ti steels. The phase diagram and CCT curve were simulated based on the chemical compositions of the J55 and J55+B,Ti steels to predict the microstructures. The results showed that the A1 and A3 temperatures decreased and, as a result, the noses of the ferrite and bainite parts of the CCT curve moved to the right. Various microstructures were formed, namely martensite, bainite, ferrite and pearlite, in accordance with the heat treatment, which had an effect on the hardness, tensile strength and toughness. Martensite was formed after water quenching, but bainite and ferrite appeared after oil quenching with the J55 specimens. On the other hand, martensite was formed, regardless of the cooling method (water quenching, oil quenching), with the J55+B,Ti specimens, because of the improvement of the hardenability caused by the addition of boron. Therefore, the J55+B,Ti specimens exhibited much higher mechanical properties than the J55 specimens, even after the tempering treatment, since the addition of Ti caused fine precipitates to be formed, which inhibited grain growth at the recrystallization temperature.

• Korean Journal of Materials Research
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• v.8 no.7
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• pp.648-652
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• 1998

TIG remelting was performed to harden the surface of automobile earn shaft. Multipass remelting was conducted in longitudinal direction under argon gas atmosphere. The microstructure of as-east earn shaft was gray iron which consisted of flake graphite and pearlitic matrix. The remelted area had microstructue of both fine pearlite and ledeburite structure that consisted of globular austenite and $Fe_3C$. Hardness for as-cast earn shaft had HRc 25~28, however it increased at remelted area to HRc 53~55. Black line was found at heat affected zone next to the fusion line, that is remelt area of previous pass, during multipass remelting. Black line was identified as graphite, which was transformed from $Fe_3C$. in the ledeburite structure. It is observed that all graphites were nucleated at $Fe_3C$. and matrix interface. High density energy laser remelting process was also applied to verify whether black line could be eliminated. However, black line was still existed as observed in TIG remelting process. Regraphitization was simulated on the ledeburitic structure specimen using Gleeble 1500 with conditions of 1100 and 100$0^{\circ}C$ for 0.5, I, 3, 5 and 1Osee. From the fact that graphite was formed even at the simulation condition of 100$0^{\circ}C$ for 0.5sec, it is seen that regraphitization is an inevitable phenomenon generated whatever processes used during multipass overlap remelting.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.10 no.2
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• pp.84-96
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• 2007

The purpose of this study was to select herbaceous plants that can be used for presenting various views and biodiversity on the extensive rooftop greening. Experiment plots were constructed in July 2005 on the rooftop of the Administration Building in the Seoul Women's University. For this experiment, planters were used to design rooftop greening. The size of a planter is 500mm${\times}$500mm${\times}$100mm and each planter has the water storage plate in the lower part of it. The soil was constructed by mixing pearlite, vermiculite, cocopeat, and leaf mold in the ratio of 6 : 2 : 1 : 1. The plot was divided into the watered plot and the dry plot. Since each plot was constructed 2 times, finally 4 planters were constructed in total. One hundred species were used for the experiment and 9 plants per species were planted in each planter. Plants were organized according to types of plants and the experiment used 86 native herbaceous plants, 6 herbs, and 8 foreign plants. The plots were monitored once a month, from July to November 2005. The length and width of plants were tape-measured and covering rate was calculated by CAD program. "SPSS 10.1" was used for a statistical analysis. The result showed no significant difference between the watered plots and the dry plots. In cases of some plants, there were statistically significant differences between the watered planter and dry planter such as follows : Astilbe chinensis and Polygonatum odoratum which are shade plants were measured as the highest value on the watered pots, and Aquilegia buergeriana, Chrysanthemum zawadskii, Calendula arvensis and Gypsophila cerastioides D.Don which are sunny plants were measured as the highest value on the dry plots. According to the final analysis of the data collected and observed for growth condition during the first year of the research, 51 species including Prunella vulgaris var. lilacina and Veronica linaiaefolia in native herbaceous plant, 5 species with Lavandula angustifolia in herbs, and 3 species with Lantana camara and Muscari armeniacum in foreign plants showed the highest growth condition. In conclusion, it is suggested that various plants including sedums could be effectively used for extensive rooftop greening to improve landscape(a view) of the rooftop and increase ecological values.

• Korean Journal of Plant Resources
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• v.23 no.1
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• pp.7-13
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• 2010

This experiment was conducted to establish the micropropagation of Calanthe discolor through multiple shoot formation from the culture of leaf, corm and root explants. Frequency of adventitious shoot formation from leaf explants was higher than those of corms and root explants. Frequency of adventitious shoot formation on medium with various concentrations of BA (0. 1.0, 3.0, and 5.0 mg/L) and NAA (0, 0.1, 0.5, and 1.0 mg/L) was tested. The maximun induction of adventitious shoot was obtained on half strength Murashige and Skoog (MS) medium supplemented with 3.0 mg/L BA and 1.0 mg/L NAA after 6 weeks of culture. Multiple shoots were transferred onto half strength MS medium with various concentrations of GA3 (0, 0.1, 0.5, 1.0, 3.0, and 5.0 mg/L). The number and length of multiple shoots on medium were highest on medium with 3.0 mg/L GA3. All the adventitious shoot grew well and rooted on half strength MS medium with 3.0 mg/L NAA. The plantlets were acclimatized up to 100% on sand with TKS-II or pearlite with TKS-II.

• Korean Journal of Materials Research
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• v.9 no.12
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• pp.1252-1262
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• 1999

The effect of microstructures on the strength-flangeability of Nb bearing hot-rolled high strength steel was investigated in order to improve the strength-flangeability of conventional TS 580MPa grades HSLA steel for the automotive wheel disc. The low temperature coiling method using 3-step controlled cooling pattern after hot rolling was effective to produce the Nb-bearing high strength steel with the polygonal ferrite and bainite duplex microstructures. It was suggested that the suppressed precipitation of grain boundary cementites and the decreased hardness difference between ferrite matrix and bainite cause the excellent stretch-flangeability of ferrite-bainite duplex microstructure steel. Therefore, the formation and propagation of microcracks were suppressed relative to the conventional HSLA steel with ferrite and pearlite microstructure. In addition, the elongation was improved as compared with that of hot-rolled steel sheets using conventional early cooling pattern because the volume fraction of polygonal ferrite was increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.41 no.8
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• pp.721-728
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• 2017

High-grade gray cast iron (HCI350) was prepared by adding Cr, Mo and Cu to the gray cast iron (GC300). Their microstructure, mechanical properties and fatigue strength were studied. Cast iron was made from round bar and plate-type castings, and was cut and polished to measure the percentage of each microstructure. The size of flake graphite decreased due to additives, while the structure of high density pearlite increased in volume percentage improving the tensile strength and fatigue strength. Based on the fatigue life data obtained from the fatigue test results, the probability - stress - life (P-S-N) curve was calculated using the 2-parameter Weibull distribution to which the maximum likelihood method was applied. The P-S-N curve showed that the fatigue strength of HCI350 was significantly improved and the dispersion of life data was lower than that of GC300. However, the fatigue life according to fatigue stress alleviation increased further. Data for reliability life design was presented by quantitatively showing the allowable stress value for the required life cycle number using the calculated P-S-N curve.