• Journal of the Korean GEO-environmental Society
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• v.21 no.8
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• pp.5-13
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• 2020

During the construction of underground space expansion of old facilities, it is necessary to secure temporary residence space for existing residents as well as noise and vibration issues during construction, and in the case of commercial, industrial, and social use, damage is expected from suspension of the use of facilities. There is a need for a technology that minimizes noise and vibration during underground expansion, enabling the use of existing facilities even during construction. In this study, a practical underground extension model is proposed by analyzing the behavior of the temporary structure and the surrounding ground as a result of measurement at each construction stage for a actual construction site. In order to solve the problems that occurred during construction, the basement slabs were placed in advance after the initial excavation. The measurement results (building inclinometer, crack measurement system, structure inclinometer and surface settlement meter) at the site were reviewed to analyze the behavior of the temporary structure and surrounding ground. As a result, it was confirmed that the inclinometer of the building and the structural inclinometer showed a tendency that the displacement after the slab line was placed was reduced or converged. The placement of basement slabs during underground extension not only relived the noise and vibration problems during construction, but also secured the stability of structures.

• Journal of the Korean Geotechnical Society
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• v.18 no.4
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• pp.339-347
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• 2002

An in-situ experiment was performed to evaluate the pullout resistance capacity of chains which is used as a reinforcement of reinforced earth wall. It was also considered that chain was combined with a bar or L-type steel angle by the transverse reinforcement member in the experiment. About 80 pullout tests were peformed with varying the lengths of chain(2.0m, 2.5m, and 3.0m), the combination of each transverse members(chain only, chain＋bar, or chain＋angle), and the vertical placement of reinforcements. In the case that uses a chain only and a chain combined with bar, the maximum displacement was about 150mm and load continuously increased to the ultimate tensile strength of chain, and then tension failure of chains occurred. But in the case of a chain combined with angle, the displacement decreased to about 100mm and so it was expected that this combination can constrain the displacement of chain. On the other hand, comparing the yielding pullout load measured in the field to that calculated by theoretical equation, it is shown that measured values are 1.2~3.0 times greater than those of calculated values according to the length of chain, normal vertical stress, and the combination of chain with transverse members. However, the difference in the increment of yielding pullout load between bar and angle is not clear but it appears almost the same increment. It is expected that chain can be safely used as reinforcements of reinforced earth wall, although a theoretical estimation of the pullout resistance capability of chain is too conservative.

• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.3
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• pp.292-298
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• 2016

In this research, considering the practical situation of separated placing method for mass concrete structure, an efficient method of controlling the heat of hydration is suggested by comparing between the simulated values and actual measurements conducted with the optimum mix design obtained from the various mix conditions with different types and amount of supplementary cementitious materials(SCMs). As the result of the research, firstly, the optimum mix designs for top and bottom layers were determined by Midas gen as OPC to FA of 85 to 15, and OPC to FA to BS of 50 to 20 to 30, respectively. The concrete mixtures prepared with the mix designs determined from the simulation satisfied the target performance range in slump, air content and compressive strength. Additionally, from temperature measurement for the actual mass concrete placed during spring, the maximum temperature difference between surface and core was about $10^{\circ}C$ with 59 and $49^{\circ}C$ for top and bottom layers, respectively, and 1.4 of cracking index was obtained. Therefore, considering the practical conditions of mass concrete construction, it is considered that the different heat of hydration method using different mix designs with SCMs can be an efficient method for controlling thermal cracking and settling cracking of mass concrete.

• Korean Journal of Organic Agriculture
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• v.24 no.4
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• pp.907-917
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• 2016

This study aimed at improving the method of oil cake application in maize. The experiment was conducted during 2 years at NAS (National Institute of Agricultural Sciences) experimental field, located in Wanju-kun, Jeollabuk-do. Growth factors and nutrient use efficiency were evaluated depending on oil cake application depth, placement, and application rate. Difference in oil cake application method and depth was tested in 2012 and different placements of oil cake application were compared in 2013. Plant height, SPAD value, and dry weight of stem and corn were investigated. SPAD value, dry weight of stem and corn were significantly higher in oil cake banding treatment (OB5, 5 cm depth) as compared to others application methods, i.e. spreading (OS0), deep banding (OB10) and banding + spreading (OB5S). In addition, dry weight of stem and corn of banding treatments (OBL, OBLL) on rhizosphere and in between row (OBR) were higher than spreading treatment (OSP). Furthermore, in case of reduced application rate in additional fertilization did not decrease dry weight of corn and increased nutrient use efficiency. Therefore, it is concluded that banding application in 5 cm-depth and rhizosphere can improve growth and nutrient use efficiency in maize production.

• Korean Journal of Soil Science and Fertilizer
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• v.28 no.4
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• pp.312-318
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• 1995

To investigate the effect of N split application on the increasing ratio of yield and the yield of rice, urea and slow-releasing complex for sideband placement of fertilizer were applied in Jeonbuk series of Honam plain area. Increasing ratio of yield by N split application was higher in puddled drill seeding (PDS) than flooded direct seeding surface (FDSS) under split application of 40-0-30-30% and 70-0-0-30% at basal, 3 leaf, 5 leaf and panicle initiation stage, respectively. It was also higher in LCU application of 70 % of total urea amount than urea application but was not different between two methods of seeding in urea application. Nitrogen ratio transfered to rough grain of rice was higher in FDSS than PDS, errespective of methed of split application, except for the split application of 0, 40, 30 and 30% N fertilizer at basal, 3 leaf, 5 leaf and panicle initiation stage, respectively. Nitrogen amount outflowed by artificial drainage for paddy field drying in a day after application of fertilizer was 1,134g/10a in PDS. $NH_4-N$ incerased higher in PDS than FDSS under split application of urea, while was versa under LCU application.

• The Journal of Korean Society for School & Community Health Education
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• v.11 no.1
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• pp.135-148
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• 2010

Objectives: In this study, knowledge of environmental disease, experience of environmental health education and necessity of environmental health education of elementary school pupils were compared and analyzed. Methods: The population of this study was from grade 1 to 6 elementary school pupils in Ulsan city, Korea. Five elementary schools were randomly selected from Ulsan City. Seven hundred and twenty-eight responses from the five schools were analyzed (seventy-two were excluded). A self-administered questionnaire measuring sociodemographic variables, Knowledge of environment related disease(atopic dermatitis, asthma etc), as well as educational experience and necessity of environmental health education was analyzed. The survey results were analyzed using SPSS-PC Program 12.0 and the following results by implementing Frequency Analysis, Cross-tabulation Analysis and ANOVA are as follows. Result: Pupils of lower grades more informed than those of higher grades about atopic dermatitis. Among asthma sufferers, many responded that symptoms occurred or improved during the lower grades of elementary school. In terms of the lifestyles of patients with atopic dermatitis or asthma, female pupils, especially those in the lower grades, tended to make changes in their daily habits based on their disease. Also, parents tended to intervene/mediate more in the dietary habits and personal hygiene habits of lower-grade pupils compared to their higher-grade counterparts. Personal hygiene education is currently not provided in schools, and upper-grade pupils have more experience with personal hygiene education compared to lower grade pupils. 430 (59.0%) of pupils replied that education about personal hygiene is necessary in their curriculum. 490 (67.3%) of elementary pupils are aware of the close connection between education in hygiene and human health. When asked if education in hygiene should also be undertaken by teachers and parents, 406 (55.7%) students said that it should be done. Conclusions: Developing a concrete health education program and raising instructors' awareness of the necessity for education in hygiene. Placement of professionals in the personal hygiene education field, is important to provide good health education for elementary school pupils.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.493-500
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• 2017

Co-operative education and internships are generally treated as an alternative way to increase the employment rate by resolving the mismatch between college education and the industrial needs of the job specification. Based on a questionnaire survey on Korean universities, this study examined the current status of programs and the operating mechanism for co-operative education and internship to provide policy suggestions for promoting the depth and width of co-operative education in Korean universities. The results of the survey shows that the majority of students carry out internships on a short-term basis and the universities usually lack the capabilities for effectively running the programs of co-operative education and internships. In particular, as a part of the academic curriculum, co-operative education should be focused on the balance and effective linkage between the occupations given to students and the majors in university.

• International Journal of Highway Engineering
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• v.6 no.4 s.22
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• pp.75-89
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• 2004

Long term performance of concrete pavement significantly depends on the given construction and environmental condition. It means that random cracks and extreme crack width due to inappropriate quality control at the early age might lead to decreasing the pavement service life. The temperature and moisture during the construction, cement and aggregate types, curing condition are major components to affect the quality of the concrete pavement at the early age. First of all, the high temperature differential, that is made by increasing air temperature and the heat of cement hydration, is known as the major contributor to severe cracks. In this study, tent covering was used for controlling temperature of the concrete slab. The field measurement data indicates that the effect of the tent covering is very significant to decrease possibilities of random crack occurrence and curling stress and enhance the long-term concrete strength. HIPERPAV(High PERformance PAVing software), a program predicting the strength and stress of an earty-age concrete pavement (72 hour after placement), is used for simulating the effects of tent covering. The HIPERPAVE results showed that the section with the tent covering has higher reliability than the section without the tent covering by 22.5%. In details, reliability is increased 72.5% (without the tent covering) to 95% (with the tent covering).

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.2
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• pp.22-34
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• 2011

This paper presents the investigation results of a research on how engineers can analyze the economic effect of the ETCS(Electronic Toll Collection System) installed to minimize the vehicle delays on freeway tollgates during toll payments. This research considered this economic effect to occur in the form of vehicle passing time reductions at the ETCS, and the multi-service queuing theory was applied to estimate these values. This research found: 1) When vehicles approaching tollgates show Poisson distribution and the service time of the ETCS shows Exponential distribution, the multi-service queuing theory would be applicable for estimating vehicle passing times at toll-gates, 2) Despite the ETCS placement, exit sections of tollgates give a greater reduction of vehicle passing times than entering sections due to more delays at conventional toll payments, and 3)The ETCS would not guarantee vehicle passing time reductions all the time, because in such a case as many vehicles were queuing at the ETCS, the total delay level for a toll gate would increase greatly. In addition, in order to examine the accuracy of the estimated vehicle passing values, this research compared the values from the multi-service queuing theory with the observed values from a set of field survey values at freeway toll-gates, and found that the two values were in a good agreement with a very low error range of 1-3 seconds per vehicle. Based on this result, the multi-service queuing theory was recommended for practice.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.35-45
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• 2014

Limit equilibrium methods of slope stability analysis have been widely adopted mainly due to their simplicity and applicability. However, the conventional methods may not give reliable and convincing results for various geological conditions such as nonhomogeneous and anisotropic soils. Also, they do not take into account soil slope history nor the initial state of stress, for example excavation or fill placement. In contrast to the limit equilibrium analysis, the analysis of deformation and stress distribution by finite element method can deal with the complex loading sequence and the growth of inelastic zone with time. This paper proposes a technique to determine the critical slip surface as well as to calculate the factor of safety for shallow failure on partially saturated soil slope. Based on the effective stress field in finite element analysis, all stresses are estimated at each Gaussian point of elements. The search strategy for a noncircular critical slip surface along weak points is appropriate for rainfall-induced shallow slope failure. The change of unit weight by seepage force has an effect on the horizontal and vertical displacements on the soil slope. The Drucker-Prager failure criterion was adopted for stress-strain relation to calculate coupling hydraulic and mechanical behavior of the partially saturated soil slope.