• Journal of the Korean GEO-environmental Society
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• v.13 no.12
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• pp.81-89
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• 2012

The existing tunnel in urban area can be enlarged because of requirement of road-widening by traffic growth. The protector with rectangular cross section can be set up in the tunnel, which will be constructed for enlargement of width, to solve traffic jam around the tunnel. It is impossible to install the rockbolt in the lower area of tunnel due to a limited space between the protector and cutting surface. The objective of this study is to suggest the method of shotcrete thickness increase instead of rockbolt installation in the side wall of tunnel for the stability of tunnel. Numerical analysis was performed to evaluate displacement at the crown of tunnel, convergence of tunnel, and stress in shotcrete lining in 3-lane and 4-lane NATM tunnels enlarged from 2-lane conventional tunnel. There were three types of analysis condition, rockbolt installation, no rockbolt installation, and increase of shotcrete thickness without rockbolt in the side wall of tunnel. There was no difference on the displacement at the crown and the convergence of upper tunnel. In the lower tunnel, the convergence in case of no rockbolt installation was larger as maximum 1.3mm than that in case of rockbolt installation. The stress in shotcrete lining in case of no rockbolt installation was larger as maximum 1.3MPa than that in case of rockbolt installation. Numerical analysis was performed to compare the behavior of shotcrete with rockbolt with that of shotcrete, which its thickness was increased, without rockbolt. The shotcrete has an increase of 20%(250mm ${\rightarrow}$ 300mm, 4-lane tunnel)~25%(200mm ${\rightarrow}$ 250mm, 3-lane tunnel) in its thickness to reduce the stress in shotcrete lining. The behavior of shotcrete lining increased the shotcrete thickness by 20%~25% was similar to that of existing shotcrete lining with rockbolt.

• Journal of Korean Society of Steel Construction
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• v.22 no.5
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• pp.477-485
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• 2010

Various monitoring sensors are used to predict and detect structural damage. Smart sensors, such as glass-fiber sensors, PZT, and MEMS, among others, have replaced traditional sensors. They are now being used in many areas. This study aims to predict the damage by measuring the PZT voltage attached on the specimen by the applied impact load. In the experiment to detect damages in beam connection, simple $H-400{\times}200{\times}8{\times}13$ beams were spliced with bolts. The results of FFT between PZT sensor and accelrometer were compared to measure the sensitivity of the PZT sensor. The damage to the beam was presumed by loosening the bolt, and then the damage measurement was accompanied. Secondly, a steel $PL600{\times}65{\times}5.8$ plate beam was fabricated for the purpose of experimenting on damage measurement. Impact loading test on three different locations was carried out. Damage width varied between 6~42mm on both sides by cutting, using a steel saw. The ratio of frequencies before and after the damage was computed to quantify the damage level by using FFT, and the change in mode pattern with the increased damage was investigated to measure the damage.

• Journal of Korean Society of Forest Science
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• v.53 no.1
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• pp.62-74
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• 1981

The developed record of forest maschines and tools in West Germany, Austria and Swiss, their technical characteristics and the working methods with them have been tried to investigate through the study of literature and observation. The aim of this investigation is to find out and introduce the technical information for training our forest men with them and for improving or developing our forest maschines and tools. Although ax chosen as first report for this aim is the oldest tool in the mankind history, still this is widely using in the forest work. And this has some special working filed that any other maschines could not overcome and sometimes should be recommended in the agronomical sideview. Through this investigation several points could be proposed as the technical informations when we will try to improve our ax 1. Radius of as-face curvature is proposed to be 150 mm and it's central point to be passed at one third point near to ax-eye. 2. Cutting angle is proposed to be $30^{\circ}$, ax-thick at 12 mm distance from ax-face to be 4 mm, thick at 30 mm distance from face to be 5 to 6 mm and ax-face width to be $125{\pm}5mm$. 3. Neck size is proposed to be $3.5{\pm}0.5{\times}5.5{\pm}0.5cm$ with a little curvature and neck thick from ax-house to be more than 1.5 cm. 4. Ax weight is proposed to be 1,000 gr with the stupid back and the sharp front. 5. The handle length of ax will be followed to the arm length of our forest workers.

• Journal of Korean Society of Forest Science
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• v.87 no.1
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• pp.82-89
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• 1998

This study was carried out to investigate working time, performance, and to predict performance that related to the factor of forest road in earth work using excavator. It was found that the real working time was 503 minutes in a day. The ratio of real working time and allowance per total working time was approximately 85.7% and 14.3% individually. The rate of soil movement(Sm) to net working time was 38.6%, and earth cutting(Ec) was 32.5%. According to performance analysis, performance of earth work using excavator($0.8m^3$) in straight part was 1.4 times larger than curve part and rock work using excavator($0.8m^3$) which had breaker in straight was 9.1 times larger than earth work using excavator($0.8m^3$) which had bucket. Performance of earth work using excavator($1.0m^3$) was 1.3 times larger than using excavator($0.8m^3$) in straight and curve part. Working performance in earth work using excavator($0.8m^3$) was influenced by the conditions of radius of curve, width of roadway, slope gradient. It is not influenced by diameter and number of root stock.

• Journal of The Korean Society of Grassland and Forage Science
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• v.17 no.2
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• pp.167-176
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• 1997

A field experiment was conducted in Chungiu and Jungwon to evaluate growth characteristics, root development, dry matter yield, crude protein yield and palatability according to nitrogen fertilizer level at intercropping cultivation of sorghum $\times$ sudangrass hybrid(hereinafier referred as SSH) and soybean. Nitrogen level was six treatment of Okg, 30kg 60kg, 90kg 120kg, and 150kg per hectare, and cutting date (sorghum $\times$ sudangrass and soybean) was july 28. 1. In the SSH, plant length was increased with increasing nitrogen fertilizer from 0kg/ha to 120kg/ha, but 150kgha treatment was decreased cornpared to 120kg/ha treatment. In the soybean, plant length did not show difference among 0kg, 30kg 60kg, and 90kg per hectare, but 120kg and 150kgfha treatment was on the contrary short. In the SSH, leaf length, leaf width and leaf number were the highest in 120kg/ha treatment, but soybean showed multifarious. 2. Stem diameter of SSH was increased with increasing nitrogen fertilizer. But soybean was thick from 0kg/ha treatment to 60kg/ha treatment, while above 90kg/ha treatment was on the contrary thin. Stem of SSH was hard with increasing nitrogen fertilizer, but soybean was soft with increasing nitrogen fertilizer. Root weight (Dry matter) of SSH was increased with increasing nitrogen fertilizer. On the contrary, soybean was decreased with increasing nitrogen fertilizer. 3. In the dairy cattle and Korean native cattle, palatability according to nitrogen fertilizer was the highest at 90kgha treatment, while 120kgha treatment and 150kgha treatment was the lowest. But in the deer, 30kg/ha treatment of low nitrogen fertilizer was the highest in palatability. 4. Nitrogen content of root of SSH was increased with increasing nitrogen fertilizer(P<0.01). But in soybean, 30kg and 60kg/ha treatment were higher than 0kg, 90kg, 120kg and 150kg/ha treatment(P<0.01). Total niwogen content of soil were high at 90kg 120kg 150kgha trea~ment(P<0.01). 5. Dry matter yield was high at the 90kg 120kg and 150kgha treatment as range from 15, 262kg/ha to 15, 614kg/ha without significant difference among those, but Okgha treatment was the lowest as 11, 183kg/ha (PC 0.05). Protein content of SSH was the highest at 90kg/ha treatment as 8.3 percentage. Soybean was highest at 60kgha treatment as 22.9 percentage. Protein yield was the highest at 90kg/ha treatment as 1, 547.6kg/ha, but Okgha treatment was the lowest as 1, 022.8kg/ha (P<0.01).

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.878-885
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• 2008

The FPDs(Flat Panel Displays) such as LCD(Liquid Crystal Display) and PDP(Plasma Display Panel) and OLED(Organic Light Emitting Diode), recently, have been substituted for CRT(Cathode Ray Tube) displays because they have a convex surface, small volume, light weight and lower electric power consumption. The productivity of FPDs is greatly dependent on the area of thin glass panel with 0.6 - 0.8mm thickness because FPDs are manufactured by cutting a large-scaled thin glass panel with patterns to the required product dimensions. So FPD's industries are trying to increase the area of thin glass panel. For example, the thin glass panel size of the 8th generation is 2,200mm in width, 2,600mm in length and 0.7mm in thickness. The air flows both in the thin glass panel and in the porous PE-plate surface were modeled and analyzed, from which a working condition was estimated. The thin glass panel on the porous PE-plate surface with self-lubricating characteristics was investigated and compared with that on the square duct floating bar surface with many holes of 1mm diameter when the thin glass panel contacts the floating bar surface due to malfunction of electric power supply.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.81-91
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• 2011

This study was conducted to evaluate the necessity of the anchor lug system in continuously reinforced concrete pavement(CRCP) by comparing longitudinal displacements of CRCPs with and without anchor lugs, and to investigate the effect of horizontal cracking on CRCP performance by measuring the vertical displacements. The measurements before and after the anchor lug section was separated were conducted for 12 days in June, and for 14 days in August after the abrupt displacements according to cutting disappeared, respectively. This short term measurement results showed that when anchor lugs were installed, a daily displacement variation at any location was less than 0.1mm; therefore, longitudinal movements were negligibly small. When there were no anchor lugs, longitudinal displacements mainly occurred near the free end and the displacement variation was small; therefore, an expansion joint system seems to be employed at a CRCP terminus without installing anchor lugs. However, further studies are needed to verify the terminus behavior due to annual temperature changes. The horizontal crack width variation was ignorable and did not affect the vertical displacement of the slab. Therefore, the horizontal crack did not delaminate the slab and did not seem to reduce the structural capacity and performance of CRCP.

• Journal of Plant Biology
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• v.13 no.1
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• pp.33-46
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• 1970

Pinus densiflora stands are common secondary forest communities on infertile soils in Korea. The stands are results of long severe past biotic pressure such as cutting, burning and grazing. These could be regarded as biotic climax in Korea. Because of their prevalent occurrence, relatively simple species and age composition, and their domestic economic importance, study of their distributional patterns may give some basic knowledge for better utilization of land resources in Korea. To detect distributional patterns and interspecific associations ten pine stands, each of which was homogenious with respect to topography and physiognomy, were subjectively selected from pine stands in Kyunggi Province near Seoul in 1969 and were made object of this study. Four contiguous systematic samples of count for trees, shrubs and seedlings from belt transects were collected from homogeneous areas within ten natural pine stands. The belt transect was 64m or 128m in length, and 1m, 2m or 4m in width. Basic units within the transect ranged from 64 to 256. The data from the contiguous transects were analysed in terms of multiple split-plot experiment. Departure from randomness of stem distribution, i.e., pattern, was tested in terms of variance mean ratio. For the detection of association between species, correlation coefficient was calculated for different block sizes. The values of ${\gamma}$ were tested by the usual t-test. Fine trees within one of the stands showed significant regular distribution through out the blocks. Within other eight stands pines were randomly distributed at basic unit with 4$\times$4m, 2$\times$2m, 2$\times$1m and 1$\times$1m. One significantly clumped distribution at basic unit 2$\times$2m, however, was observed from one of the pine stands. These randomly distributed groups were themselves significantly regularly distributed throughout the blocks for four pine stands. For the other four pine stands, in addition to the random distribution at the basie unit(the primary random group), randomly distributed groups with 32m dimension(the secondary random groups) were also observed. Both the primary and the secondary random groups were significantly regularly distributed at the rest of blocks. Pine seedlings were not distributed randomly thoughout the blocks. Within three of the ten stands they were contagiously distributed. Important shrub species underneath pines such as Querus serrata, Q. acutissima, Leapedeza intermedia, Rhododendron Yedoense var. poukhanenae, Juniperus utilis, Rhododendron mucronulatum var. ciliatum shnwed consistently similar distributional pattern with the pine at each stand. The shrub species pairs; Rhododendron Yedoense var. poukhanenae/Quercus serrata, Rhododendron mucronulatum var. ciliatum/Lespedeza intermedia were significantly negatively associated from 1m to 4m dimensional block sizes but became significantly positively associated from 8m sized blocks on. On the other hand the shrub species pairs; Lespedeza intermedia/Robinia Pseudoacacia, and Lespedeza bicolor var, japonica/Lespedeza intermedia were also significnalty negatively associated from 1m to 8m sized blocks but became significantly positively associated from 16m sized blocks on. The associational pattern between Rhododendron mucronul tun var. poukhanenae and Lespedeza intermedia was not consistent throughout the stands. In some stands negative associations were observed throughout the blocks except NS 32. From these observatons micro-edaphic variation within the pine stands seems not to be great enough to cause distributinal difference of pine trees within the ten pine stands. Among each species and pine seedings, however, the edaphic variation within the pine stands may be great enought to cause distributional variation.

• Journal of Korean Society of Forest Science
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• v.87 no.2
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• pp.239-252
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• 1998

Based on forestry inventory data and various informations, this study was conducted to analyze the silvicultural activities by distance classes from forest road and to evaluate their effects in the area of Mt. Gari managed by Chunchon Regional Office of Northern Forest Management Office. The results were summarized as follows; 1) Most harvesting practice(67.9%) was done within 500m from forest roads, in the order of Pumgul, Saorang, and Kongkol forest road. And thinning practice was not related to the distance from forest road, produced $440.6m^3$, 35.7% of total thinning volume within 1,000m width along the forest roads. 2) Planting of 530,461 seedlings, 66.8% of total planting stock, in 176.9ha, 66.6% of total area within 1,000m from forest road, and supplementary planting of 46,243 seedlings was done in 15.4ha, 42.9% of total area within 500m from forest road. Areas and numbers of seedlings of two planting practices were in the order of Pumgul and Byungatur forest road. 3) Tending operation was done in 330.0ha, 60.3% of total area within 500m from forest road, and pre-commercial thinning was done in 693.6ha, 71.2% of total area. Areas of intermediate cutting practices were in the order of Pumgul, Korkol, and Saorang forest road.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.62-62
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• 2018

Pt is still considered as one of the most active electrocatalysts for ORR in alkaline fuel cells. However, the high cost and scarcity of Pt hamper the widespread commercialization of fuel cells. As a strong candidate for the replacement of Pt catalyst, silver (Ag) has been extensively studied due to its high activity, abundance, and low cost. Ag is more stable than Pt in the pH range of 8~14 as the equilibrium potential of Ag/Ag+ being ${\approx}200mV$ higher than that of Pt/PtO. However, Ag is the overall catalytic activity of Ag for oxygen reduction reaction(ORR) is still not comparable to Pt catalyst since the surface Ag atoms are approximately 10 times less active than Pt atoms. Therefore, further enhancement in the ORR activity of Ag catalysts is necessary to be competitive with current cutting-edge Pt-based catalysts. We demonstrate the architectural design of Ag catalysts, synthesized using plasma discharge in liquid phase, for enhanced ORR kinetics in alkaline media. An attractive feature of this work is that the plasma status controlled via electric-field could form the Ag nanowires or dendrites without any chemical agents. The plasma reactor was made of a Teflon vessel with an inner diameter of 80 mm and a height of 80 mm, where a pair of tungsten(W) electrodes with a diameter of 2 mm was placed horizontally. The stock solutions were made by dissolving the 5-mM AgNO3 in DI water. For the synthesis of Agnanowires, the electricfield of 3.6kVcm-1 in a 200-ml AgNO3 aqueous solution was applied across the electrodes using a bipolar pulsed power supply(Kurita, Seisakusyo Co. Ltd). The repetition rate and pulse width were fixed at 30kHz and 2.0 us, respectively. The plasma discharge was carried out for a fixed reaction time of 60 min. In case of Ag nanodendrites, the electric field of 32kVcm-1 in a 200-ml AgNO3 aqueous solution was applied and other conditions were identical to the plasma discharge in water in terms of electrode configuration, repetition rate and discharge time. Using SEM and STEM, morphology of Ag nanowires and dendrites were investigated. With 3.6 kV/cm, Ag nanowire was obtained, while Ag dendrite was constructed with 32 kV/cm. The average diameter and legth of Ag nanowireses were 50 nm and 3.5 um, and thoes values of Ag dendrites were 40 nm and 3.0 um. As a results of XPS analysis, the surface defects in the Ag nanowires facilitated O2 incorporation into the surface region via the interaction between the oxygen and the electron cloud of the adjacent Ag atoms. The catalytic activity of Ag for oxygen reduction reaction(ORR) showed that the catalytic ORR activity of Ag nanowires are much better than Ag nanodendrites, and electron transfer number of Ag nanowires is similar to that of Pt (${\approx}4$).