• Journal of the Korean Geotechnical Society
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• v.22 no.6
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• pp.27-40
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• 2006

Damage of cut-and-cover tunnel lining can be attributed to physical and mechanical factors. Physical factors include material property, reinforcement corrosion, etc. while mechanical factors include underground water pressure, vehicle loads, etc. This study is limited to the modeling of rigid circular cut and cover tunnel constructed at a depth of $1.0{\sim}1.5D$ in loose sandy ground and subjected to a vibration frequency of 100 Hz. In this study, only damages due to mechanical factors in the form of additional loads were considered. Among the different types of additional, excessive earth pressure acting on the cut-and-cover tunnel lining is considered as one of the major factors that induce deformation and damage of tunnels after the construction is completed. Excessive earth pressure may be attributed to insufficient compaction, consolidation due to self-weight of backfill soil, precipitation and vibration caused by traffic. Laboratory tunnel model tests were performed in order to determine the earth pressure acting on the tunnel lining and to investigate the applicability of existing earth pressure formulas. Based on the difference in the monitored and computed earth pressure, a factor of safety was recommended. Soil deformation mechanism around the tunnel was also presented using the picture analysis method.

• Korean Journal of Environmental Agriculture
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• v.41 no.4
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• pp.230-235
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• 2022

BACKGROUND: Ammonia gas emitted from nitrogen fertilizers applied in agricultural land is an environmental pollutant that catalyzes the formation of fine particulate matter (PM2.5). A significant portion (12-18%) of nitrogen fertilizer input for crop cultivation is emitted to the atmosphere as ammonia gas, a loss form of nitrogen fertilizer in agricultural land. The widely practiced method for fertilizer use in agricultural fields involves spraying the fertilizers on the surface of farmlands and mixing those with the soils through such means as rotary work. To test the potential reduction of ammonia emission by nitrogen fertilizers from the soil surface, we have added N, P, and K at 2 g each to the glass greenhouse soil, and the ammonia emission was analyzed. METHODS AND RESULTS: The treatment consisted of non-fertilization, surface spray (conventional fertilization), and soil depth spray at 10, 15, 20, 25, and 30 cm. Ammonia was collected using a self-manufactured vertical wind tunnel chamber, and it was quantified by the indophenol-blue method. As a result of analyzing ammonia emission after fertilizer treatments by soil depth, ammonia was emitted by the surface spray treatment immediately after spraying the fertilizer in the paddy soil, with no ammonia emission occurring at a soil depth of 10 cm to 30 cm. In the upland soil, ammonia was emitted by the surface spray treatment after 2 days of treatment, and there was no ammonia emission at a soil depth of 15 cm to 30 cm. Lettuce and Chinese cabbage treated with fertilizer at depths of 20 cm and 30 cm showed increases of fresh weight and nutrient and potassium contents. CONCLUSION(S): In conclusion, rather than the current fertilization method of spraying and mixing the fertilizers on the soil surface, deep placement of the nitrogen fertilizer in the soil at 10 cm or more in paddy fields and 15 cm or more in upland fields was considered as a better fertilization method to reduce ammonia emission.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1A
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• pp.183-190
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• 2006

Minimizing the self weight of long-span deck slabs is one of the key factors for the practical and economic design of a composite two-girder bridge. In this paper, the minimum design thickness and rebar details of prestressed concrete deck slabs for composite two-girder bridges with girder span length from 4 m to 12 m are studied based on the safety and serviceability. The bridge deck slab with minimum thickness is designed as a one-way slab considering orthotropic behavior. Then fatigue safety of the deck slab is examined. Serviceability requirements for the deck slab such as deflection and crack width limits are also examined. The result shows that rebars with diameter less than 16 mm is recommended for the improved fatigue behavior, and, for the deck slab with span length longer than 8 m, the deflection limit governs the minimum design thickness. The result also shows that, for the deck slab with span length longer than 4 m, the distribution rebar requirement in the current Korea Highway Bridge Design Code is not sufficient to maintain the structural continuity in bridge axis as expected from the deck slab with span length shorter than 3 m.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.707-717
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• 2006

As an alternative to conventional prestressed concrete (PSC) girders, various types of PSC girders are either under development or have already been applied in bridge structures. Incrementally prestressed concrete girder is one of these newly developed girders. According to the design concept, these new types of PSC girders have the advantages of requiring less self-weight while having the capability of longer spans. However, the dynamic interaction between bridge superstructures and passing trains is one of the critical issues concerning these railway bridges designed with more flexibility. Therefore, it is very important to evaluate modal parameters of newly designed bridges before doing dynamic analyses. In the present paper, a 25 meters long full scale PSC girder was fabricated as a test specimen and modal testing was carried out to evaluate modal parameters including natural frequencies and modal damping ratios at every prestressing stage. During the modal testing, a digitally controlled vibration exciter as well as an impact hammer is applied, in order to obtain precise frequency response functions and the modal parameters are evaluated varying with construction stages. Prestressed force effects on changes of modal parameters are analyzed at every incremental prestressing stage. With the application of reliable properties from modal experiments, estimation of dynamic performances of PSC girder railway bridges can be obtained from various parametric studies on dynamic behavior under the passage of moving train. Dynamic displacements, impact factor, acceleration of the slab, end rotation of the girder, and other important dynamic performance parameters are checked with various speeds of the train.

• Journal of the Korea Institute of Construction Safety
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• v.6 no.1
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• pp.12-18
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• 2024

High-rise, large-scale, and diversification of buildings are possible, and the reduction of concrete cross-sections reduces the weight of the structure, thereby increasing or decreasing the height of the floor, securing a large number of floors at the same height, securing a large effective space, and reducing the amount of materials, rebar, and concrete used for designating the foundation floor. In terms of site construction and quality, a low water binder ratio can reduce the occurrence of dry shrinkage and minimize bleeding on the concrete surface. It has the advantage of securing self-fulfilling properties by improving fluidity by using high-performance sensitizers, making it easier to construct the site, and shortening the mold removal period by expressing early strength of concrete. In particular, with the rapid development of concrete-related construction technology in recent years, the application of ultra-high-strength concrete with a design standard strength of 100 MPa or higher is expanding in high-rise buildings. However, although high-rise buildings with more than 120 stories have recently been ordered or scheduled in Korea, the research results of developing ultra-high-strength concrete with more than 130 MPa class considering field applicability and testing and evaluating the actual applicability in the field are insufficient. In this study, in order to confirm the applicability of ultra-high-strength concrete in the field, a preliminary experiment for the member of a reduced simulation was conducted to find the optimal mixing ratio studied through various indoor basic experiments. After that, 130 MPa-class ultra-high-strength concrete was produced in a ready-mixed concrete factory in a mock member similar to the life size, and the flow characteristics, strength characteristics, and hydration heat of concrete were experimentally studied through on-site pump pressing.

• The Journal of the Convergence on Culture Technology
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• v.10 no.2
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• pp.499-503
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• 2024

Broadcasting programs are provided to various media such as Internet replay, OTT, and IPTV services as well as self-broadcasting. In this case, it is very important to provide keywords for search that represent the characteristics of the content well. Broadcasters mainly use the method of manually entering key keywords in the production process and the archive process. This method is insufficient in terms of quantity to secure core metadata, and also reveals limitations in recommending and using content in other media services. This study supports securing a large number of metadata by utilizing closed caption data pre-archived through the DTV closed captioning server developed in EBS. First, core metadata was automatically extracted by applying Google's natural language AI technology. The next step is to propose a method of finding core metadata by reflecting priorities and content characteristics as core research contents. As a technology to obtain differentiated metadata weights, the importance was classified by applying the TF-IDF calculation method. Successful weight data were obtained as a result of the experiment. The string metadata obtained by this study, when combined with future string similarity measurement studies, becomes the basis for securing sophisticated content recommendation metadata from content services provided to other media.

• Horticultural Science & Technology
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• v.29 no.6
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• pp.645-650
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• 2011

Pear cultivar 'Supergold' (Pyrus pyrifolia var. culta Nakai) was originated from the cross between 'Chuwhangbae' and 'Manpungbae' with the aims of improving the fruit quality of 'Chuwhangbae' cultivar at Pear Research Station of National Institute of Horticultural & Herbal Science, Rural Development Administration in 1994. 'Supergold' was preliminarily selected in 2002 and named in 2008. The tree shows a vigorous growth habit and semi-spread characters like as 'Manpungbae'. Furthermore, it has sufficient flowers and carries abundant pollen grains, so it can also be used as a pollinator. 'Supergold' is highly resistant to black leaf spot (Alternaria kikuchiana) in the field condition. The optimum harvest time is around Sep. 11th, which is ahead of 'Whangkeumbae' about 5 days in the harvest period. The fruit shape is oblate and fruit skin color is greenish-white at harvesting time. The average weight of fruit is 570 g, and the soluble solids content is $13.6\;^{\circ}Brix$. The flesh is very soft and juicy, and renders good eating quality. Shelf life is about 6 months under the cold storage condition. To determine the self-incompatibility (SI) genotype of 'Supergold' pear cultivar, it was crossed with other cultivars of which SI genotypes have already known. The result of cross-pollinations of 'Supergold' with other cultivars showed relatively high rates of fruit set from 64.5% to 91.0%, except for the cross with pollens of 'Nijisseiki' that represented only 28.8% of fruiting rate. Although sometimes the stigma of 'Supergold' crossed with 'Hayatama', 'Chojuro', and 'Nijisseiki' showed malformed pollen tube tips, 'Supergold' is generally supposed to have cross-compatibility with all other pollen donor cultivars. It is considered that the S-allele of 'Supergold' is $S_3S_4$, which is based on the result of PCR-RFLP.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.1 no.1
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• pp.11-23
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• 2003

A study on the electrolytic dissolution of SUS-304 and Inconel-600 specimen was carried out in neutral salt electrolyte to evaluate the applicability of electrochemical decontamination process for recycle or self disposal with authorization of large amount of metallic wastes contaminated with uranium compounds generated by dismantling a retired uranium conversion plant in Korea. Although the best electrolytic dissolution performance for the specimens was observed in a Na2s04 electrolyte, a NaNO$_3$ neutral salt electrolyte, in which about 30% for SUS-304 and the same for Inconel-600 in the weight loss was shown in comparison with that in a Na$_2$SO$_4$ solution, was selected as an electrolyte for the electrochemical decontamination of metallic wastes with the consideration on the surface of system components contacted with nitric acid and the compatibility with lagoon wastes generated during the facility operation. The effects of current density, electrolytic dissolution time, and concentration of NaNO$_3$ on the electrolytic dissolution of the specimens were investigated. On the basis of the results obtained through the basic inactive experiments, electrochemical decontamination tests using the specimens contaminated with uranium compounds such as UO$_2$, AUC (ammonium uranyl carbonate) and ADU (ammonium diuranate) taken from an uranium conversion facility were performed in 1M NaNO$_3$ solution with the current density or In mA/$\textrm{cm}^2$. it was verified that the electrochemical decontamination of the metallic wastes contaminated uranium compounds was quite successful in a NaNO$_3$ neutral salt electrolyte by reducing $\alpha$ and $\beta$ radioactivities below the level of self disposal within 10 minutes regardless of the type of contaminants and the degree of contamination.

• Journal of Nutrition and Health
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• v.50 no.5
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• pp.460-471
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• 2017

Purpose: The purpose of this cross-sectional study was to investigate intake-related factors of energy drinks and educational needs regarding energy drinks in female high school students. Methods: Subjects were 340 female high school students in Incheon, and data were collected using self-administered questionnaires. Statistical analysis was performed using the SPSS 20.0 program. Results: Subjects who had drunk energy drinks were 74.3% (249 subjects) of all subjects. The first time they drank an energy drink was significantly associated with grade (p < 0.05). In 75.1% of 249 subjects who had drunk energy drinks, the places for buying energy drinks were supermarkets and convenience stores near their homes. For the effects of energy drink intake, sleeplessness (44.6%) and no effect (41.7%) were cited, and 24.5% experienced side effects such as palpitation, tremors, etc. The scores for self-diagnosis of caffeine addiction were significantly higher in the low weight group compared to the overweight group (p < 0.05). The degree of caffeine addiction was significantly associated with effects of energy drink intake (p < 0.001) and type of side effects (p < 0.001). Willingness to stop consuming energy drinks (p < 0.001) and necessity of nutrition education about energy drinks (p < 0.05) were significantly lower in the caffeine addiction group compared to the general group. About 75.0% of subjects wanted to be educated about the side effects of energy drinks and caffeine. Conclusion: This study shows that female high school students need proper education about the effects of intake of energy drinks. Therefore, guidelines and a nutrition education program right intake of energy drinks should be provided as well as campaigns concerning the side effects of energy drinks and caffeine in female high school students.

• Journal of dental hygiene science
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• v.12 no.6
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• pp.558-565
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• 2012

The purpose of this study was to work related musculoskeletal disorders are a major. Occupational disease of the dental care profession is no exception. The survey was self-reported questionars of 300 dental hygienists that 268 dental hygienists reply to self-reported survey. This study results are as follows: Subjects of research analyzing the degree of physical musculoskeletal disorders pain, shoulder 90.3%, neck 89.2%, leg 83.6%, 81.7% back, hand/wrist/fingers 75.7%, arm/elbow, according to 52.8%. Therefore the work province of the research object people the musculoskeletal disorders appeared different. Generally characteristic was taller dental hygienists lower back pain and were out of less weight, study subjects had neck and arm pain. 29~33 year-old age the shoulder, over the age of 34 the arm/elbow to be high (p<0.05). Working environment to become a career, the more hand/wrist/fingers and the pain increased (p<0.05). The neck, shoulders (p<0.05), arm (p<0.01), waist high in the 3~4 years experience. And leg/foot was in the 1~2 years experience. This increase in working hours had increased pain in the neck but the hand/wrist/finger pain in the small hours of experience in the high pain(p<0.01). Conclusion of the musculoskeletal disorders of the dental hygienists often than the average for this risk is recognized. When it occurs early in treatment can be simple, but time is left to revert to normal when you do not already. Therefore, maintaining proper posture and dental hygienists, pain or fatigue appeared to accumulate immediately treated continued efforts are needed.