• Journal of Korean Tunnelling and Underground Space Association
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• v.25 no.5
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• pp.357-371
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• 2023

In cable tunnel construction using TBM, the vertical shaft is an essential structure for entrance and exit of TBM equipment and power lines. Since a shaft penetrates the ground vertically, it often encounters rock mass. Blasting or rock splitting methods, which are mainly used to the rock excavation, cause public complaints due to the noise, vibration and road occupation. Therefore, mechanical excavation using vertical shaft excavation machine are considered as an alternative to the conventional methods. However, at the current level of technology, the vertical excavation machine has limitation in its performance when applied for high strength rock with a compressive strength of more than 120 MPa. In this study, the potential utilization of waterjet technology as an excavation assistance method was investigated to improve mechanical excavation performance in the hard rock formations. Rock cutting experiments were conducted to verify the cutting performance of the abrasive waterjet. Based on the experimental result, it was found that ensuring excavation performance with respect to changing in ground conditions can be achieved by adjusting waterjet parameters such as standoff distance, traverse speed and water pressure. In addition, based on the relationship between excavation performance, uniaxial compressive strength and RQD, it was suggested that excavation performance could be improved by artificially creating joints using the abrasive waterjet. It is expected that these research results can be utilized as fundamental data for the introduction of vertical shaft excavation machines in the future.

• Korean Journal of Environment and Ecology
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• v.21 no.4
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• pp.318-335
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• 2007

Floral study and present vegetation survey were conducted at a representative reclaimed wetland located behind the Rural Research Institute at Ansan, Gyeonggi-do. The importance values were calculated from the ground cover and frequency of recorded species within quadrats and detrended canonical correspondence analysis was conducted using environment variables, such as total nitrogen, electric conductivity, available phosphate, nitrate nitrogen and the distance from the inner roads. And basal areas for the trees encroaching on the reclaimed wetland were estimated to take a look at the on-going situation about the succession routes on land. As a result, 46 families and 158 species of plants were recorded and Pragmites communis was found to be a dominant species as the present vegetation. The ordination analysis results showed that species distribution was purposely explained by total nitrogen in soil and its content in nitrate nitrogen. The invasion of Robinia pseudoacacia and Pinus rigida whose basal areas were $22.3m^2$ and $1.6m^2$ respectively, into the interior areas of the reclaimed wetland was found to cause a disturbance making some parts of the wetland into land. The zoning program using water level control and migratory roads is becoming a contributing factor in destroying a wetland, so it's suggested that some adjustments should be needed to take care of it.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2002.05a
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• pp.12-16
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• 2002

Soil, ground water and sea bed are exposed to continuous accumulation of polluted materials causing serious environmental damage. It has been reported that such pollution causes a massive mortality of fish stock in rivers by the resuspension of toxic chemicals during strong wind conditions. Therefore, it becomes apparent that there is an immediate demand for the restoration treatment of polluted river bed (or sea bed) sediment layers. Pollution levels of major rivers and ports such as Pal-dang, Kyung-an rivers, Ma-san port are becoming public concern and are posing a serious environmental threat. In particular, the pollution of Shi-hwa river has become a nation wide issue for last few years. In spite of such public concern, the pollution level of such rivers or port are getting worse everyday. In this study, an environmentally sound engineering package is introduced which helps to restore the polluted river bed or sea bed sediments. This engineering package is consisted of a suction facility followed by a series of mechanical, chemical as well as biological treatment units. The suction facility is designed to minimize the secondary pollution due to the resuspension of toxic materials during suction. The sea bed cleaning engineering package is designed to be installed on the top of a floating barge. Such combination of environmental plant and shipbuilding technology provides a cost-effective solution, minimizing the cost involved in the transportation between suction and treatment facilities.

• Asian-Australasian Journal of Animal Sciences
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• v.8 no.2
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• pp.113-118
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• 1995

Eighteen Holstein Friesian ${\times}$ Native heifers with an average live weight of $175.4{\pm}27.8kg$ were allotted to 3 dietary groups. All animals were kept individually in a stanchion barn with free access to water and urea-treated rice straw (UTS). The supplemented feeds were as follows: Group (Gr) 1 - concentrate mixture (15% CP) at 1% body weight (BW), Gr 2 - concentrate mixture at 0.7% BW + free licking of multinutrient block (MNB), Gr 3 - as Gr 2 + 0.3% BW ground com. Multinutrient block composed of 20% mineral mixture, 10% urea, 18% molasses, 20% soybean meal, 22% sesame meal, 10% cement, 0.15 million IU and 50 IU/kg MNB of vitamin A and E. The experimental period lasted 12 weeks. The result revealed that MNB enhanced intake of UTS and total dry matter intake. Animals in Gr 3 consumed a higher amount of feed than the other 2 groups, thus resulting in the highest live weight gain and tended to possess the best feed conversion ratio. Heifers in Gr 2 also performed better than Gr 1 although the difference was not significant. Average MNB intake found to be 0.65 kg/day. Feed cost per kg gain was not significantly different amon groups. However if the cost of MNB could be lower, it would benefit the production cost of animals. The advantage of MNB is the safety of using a high level of urea. Although it was supplemented to UTS which also contained non-protein nitrogen (NPN), no toxic sign was shown. The results indicated that MNB could be partially substituted to concentrate mixture and it was even better when used incombination with soluble carbohydrate feed.

• Korean Journal of Soil Science and Fertilizer
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• v.27 no.4
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• pp.296-302
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• 1994

To alter the paddy field to upland, mole drainages were constructed under 30cm of the surface of(Jeon buk silt loam) which is not appropriate for cultivation of upland crops. Intervals of the moles were 50cm, 100cm and 150cm and diverted to upland for soybean cultivation. By construction of the mole drainage, about 75% to 45% of the rainfall was drained and the ground water level was maintained below 40cm. After a year of drainage, the blocky surface was changed to granular or nutty structure which is common in upland fields. Oxidation was progressed to the deep layer because of soil dryness. Soybean yield were increased by 11% to 22% in the mole drained plots, but wet injury was occurred in the nontreated check plot with relatively poor growth status.

• Korean Journal of Environment and Ecology
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• v.8 no.1
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• pp.74-77
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• 1994

To examine the effects of gibberelin treatment on seed germination of five Viola species - Viola variegata, Viola dissecta var, chaerophylloides, Viola collina, Viola hirtipes and Viola manshrica - in Wonju district, pretreated seeds of five species were sowed on Jiffy strips with mixed soil(sand： peat moss： perlite： vermiculite, 1:1:1:1, v/v) in 25, May 1994. Seeds were soaked in 5, 25, 50ppm gibberelin solution and ground water during 24 hours. Seed germination rate was measured and compared among species and treatments. Seed germination rate of Viola hirtipes was differed higly significant among pretreatments, but those of other species did not significant at 5of level. In general GA$_3$pretreatment raised seed germination rate of 5 Viola species, and proper concentration of GA$_3$was 25~50ppm.

• Journal of the Korean GEO-environmental Society
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• v.16 no.3
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• pp.15-21
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• 2015

Since the introduction of 'the rule for computerizing subsoil investigation results and its application' in 2007, the DB construction of the national geotechnical information by Ministry of Land, Transport and Maritime Affairs (MOLTMA) has been performed. According to the Integrated DB Center of National Geotechnical Information, there have been 180 thousands borehole information stored in the system. In this study, the time-series analyses of precision on the most used information, the depth of stratum and ground water level, were performed to evaluate the effect of the initiation of the rule established in 2007. The precisions were evaluated based on the statistical analyses using kurtosis and normal distribution. Based on the results, the increase of precision after 2007 and the affirmative effects of the rule established in 2007 are confirmed. Furthermore, the precision of the regional information can be achieved with the precision analyses on the information from various areas.

• Nuclear Engineering and Technology
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• v.45 no.1
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• pp.1-12
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• 2013

This paper describes the radiation doses to human and non-human biota in the Republic of Korea, as a result of the Fukushima nuclear accident. By using the measured airborne activity and ground deposition, the effective and thyroid doses of five human age groups (infant, 5 years, 10 years, 15 years and adult) were estimated by the ECOSYS code, and the whole body absorbed dose rate of the eight Korean reference animals and plants (RAPs) was estimated by the K-BIOTA (the Korean computer code to assess the risk of radioactivity to wildlife). The first-year effective and thyroid human doses ranged from 5.7E-5 mSv in the infant group to 2.0E-4 mSv in the 5 years group, and from 5.0E-4 mSv in the infant group to 3.4E-3 mSv in the 5 years group, respectively. The life-time (70 years) effective and thyroid human doses ranged from 1.5E-4 mSv in the infant group to 3.0E-4 mSv in the 5 years group, and from 6.0E-4 mSv in the infant group to 3.5E-3 mSv in the 5 years group, respectively. The estimated maximum whole body absorbed dose rate to the Korean RAPs was 6.7E-7 mGy/d for a snake living in soil (terrestrial biota), and 2.0E-5 mGy/d for freshwater fish (aquatic biota), both of which were far less than the generic dose criteria to protect biota from ionizing radiation. Also, the screening level assessment for ERICA's (Environmental Risks from Ionizing Contaminants: Assessments and management) limiting organisms showed that the risk quotient (RQ) for the estimated maximum soil and water activity was significantly less than unity for both the terrestrial and freshwater organisms. Conclusively, the radiological risk of the radioactivity released into the environment by the Fukushima nuclear accident to the public and the non-human biota in the republic of Korea is considered negligible.

• Geotechnical Engineering
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• v.4 no.4
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• pp.39-50
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• 1988

Until now, most probabilistic approaches to the slope stability analysis have been accomplished on the arc failure surface without load. In this study, the relationships between the probability of failure and the safety factor are investigated when the shape of failure is logarithmic spiral on the homogeneous slope with ground water level, the probability distributions of the load and the strength parameter of soil being assumed as normal distribution, log-normal distribution and beta distribution. The results obtained are as follows; 1. For the same safety factor, the design of slope is more reasonable by using the probability of failure than by the safety factor because the probability of failure is increased as the coefficient of variation is increased. 2, The safety factor is more reasonably determined by the coefficient of variation of the strength parameter than by the field condition when the safety factor is applied to design of slope.

• Korean Journal of Environment and Ecology
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• v.9 no.1
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• pp.56-61
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• 1995

To examine the effects of gibberelin treatment on seed germination of six wild herbaceous species -Dicentra spectabilis, Aster pekinensis, Agastache rugosa, Elsoholtzia ciliata, Boehmeria tricuspis and Pulsatillia cerrma var. chaerophyiloides - in Kangwon-do, pretreated seeds of five species were sowed on plastic pots with mixed soil(sand：peat moss：perlite： vermiculite, 1：1：1：1, v/v) in 23,April 1995. Seeds were soaked in 25,50 ppm gibberelin solution and ground water during 24 hours. Pretreated seeds of Pulsatiilia cerrma var. chaerophylloides were sowed on nursery soil in 1, June 1995. Seed pretreatments in 31, May 1995 were same method. Seed germination rate was measured and compared among species and treatments. Seed germination rate of Dicentra spectabilis, Agastache rugosa and Elsoholtzia ciliata was differed higly significant among pretreatments ,but those of that of Aster pekinensis, Boehmeria tricuspis and Pulsatillia cerrma var chaerophylloides did not significant at 5% level. Gibberelin pretreatment raised seed germination rate of Dicentra spectabilis and Agastaohe rugosa and proper concentration of GA$_3$ was 25ppm and seed germination rate of Elsoholtzia ciliata was highest at GA$_3$ 50ppm plot. The utilization of wild herbaceous species were discussed.