• Journal of Ecology and Environment
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• v.38 no.2
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• pp.133-143
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• 2015

Freshwater macrophytes improve the structural heterogeneity of microhabitats in water, often providing an important habitat for zooplankton. Some studies have focused on the overall influence of macrophytes on zooplankton, but the effects of macrophyte in relation to different habitat characteristics of zooplankton (e.g., epiphytic and pelagic) have not been intensively studied. We hypothesized that different habitat structures (i.e., macrophyte habitat) would strongly affect zooplankton distribution. We investigated zooplankton density and diversity, macrophyte characteristics (dry weight and species number), and environmental parameters in 40 shallow wetlands in South Korea. Patterns in the data were analyzed using a self-organizing map (SOM), which extracts information through competitive and adaptive properties. A total of 20 variables (11 environmental parameters and 9 zooplankton groups) were patterned onto the SOM. Based on a U-matrix, 3 clusters were identified from the model. Zooplankton assemblages were positively related to macrophyte characteristics (i.e., dry weight and species number). In particular, epiphytic species (i.e., epiphytic rotifers and cladocerans) exhibited a clear relationship with macrophyte characteristics, while large biomass and greater numbers of macrophyte species supported high zooplankton assemblages. Consequently, habitat heterogeneity in the macrophyte bed was recognized as an important factor to determine zooplankton distribution, particularly in epiphytic species. The results indicate that macrophytes are critical for heterogeneity in lentic freshwater ecosystems, and the inclusion of diverse plant species in wetland construction or restoration schemes is expected to generate ecologically healthy food webs.

• Journal of the Korean Geotechnical Society
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• v.20 no.7
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• pp.159-169
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• 2004

Surface failures of slopes in weathered soil are caused by infiltration due to prolonged rainfall. These failures are mainly triggered by the deepening of the wetting band accompanied by a decrease in suction induced by the infiltrating water. This paper reports trends of rainfall-induced wetting band depth in two types of weathered soils that are commonly found in Korea. Both theoretical and numerical analyses are presented based on the soil-water characteristic curve (SWCC) obtained using filter paper as well as tensiometer tests. It is found that the magnitude of wetting front suction plays a key role in the stability of slopes in weathered soils. Theoretical analysis based on modified Green and Ampt model tends to underestimate the wetting band depth for typical Korean weathered soils. It was also deduced that for Korean weathered soils, the factor of safety drops rapidly once the wetting band depth of 1.2 m is reached.

• Journal of the Korean housing association
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• v.22 no.4
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• pp.43-50
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• 2011

In an aging society, as the number of people with disabilities increases concerns are raised about the quality of life of these people and their access to a safe environment becomes important. The purpose of this study is to find out the value of accessibility as an attribute of housing. To estimate the value of accessible, barrier-free housing, this study uses the Contingent Valuation Method (CVM) and analyzes the factors which affect the Willingness To Pay (WTP) of survey respondents by using Survival Analysis. In addition, the importance and satisfaction of barrier-free facilities in the dwellings of survey respondents was investigated. Since aging could be an important factor in influencing the need for accessibility, this study surveyed two age groups, one group (212 respondents) of people below the age of 65 and the other (162 respondents) of people above 65. The results of this study show that respondents would pay on average 2.67% more for being barrier-free when answering an open-ended question and 3.87% more for barrier-free housing when using the double referendum model. This is the increase in value that the respondents perceive as a consequence of removing all the architectural barriers from a dwelling. On average, elderly respondents would pay 2.99% of housing price for accessible features compared to 4.40% of the younger group. However, if the elderly who have willingness to pay for accessibility, the value the older group put on barrier-free housing was higher than the value perceived by the younger group. Factors that influence the WTP are importance of barrier-free facilities, education level and housing type. The value of dwellings without barriers estimated in this study shows the potential size and value of this kind of housing market to the housing development sector.

• Convergence Security Journal
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• v.14 no.3_2
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• pp.23-35
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• 2014

This study aims to verify the relationship between customer orientation and job stress due to the degree of emotional labor on security agents. Objects of study are from 10 security companies, randomly selected from those registered on the Regional Police Agencies in Daejeon and Chungnam, from November 10th to 20th, 2013; thirty agents from each company, or three-hundred in total, were selected as research subjects by random sampling method. Twenty-five subjects were excluded for poor response contents and/or low reliability. Thus, only 275 subjects were included in actual analysis. The research tool was the questionnaire which was re-composed on the basis of domestic/overseas preliminary studies, while the data was processed through the frequency analysis, the reliability analysis, the confirmatory factor analysis and structure model analysis, using SPSS version 19.0 and AMOS 17.0 statistics package. Through the data analysis following the research methods above, the conclusion was acquired as follows. First, as job stress of security agents decreased, customer orientation increased. Second, the group of security agents with lower level of emotional labor positively affected job stress and customer orientation.

• Culinary science and hospitality research
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• v.23 no.3
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• pp.196-206
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• 2017

This study intended to examine the Korean restaurant customer's recognition about GIAP and to measure the reliability for them, and to figure out their effects on the customer's satisfaction and revisit intentions. Accordingly, research model had been set up and also hypotheses was made up according to pre-studies and pre-investigation results. Factor analysis and reliability analysis were concluded as valid results by the Cronbach's Alph for GIAP, customer satisfaction and revisit intention each other. Firstly, the effect of GIAP on the customer satisfaction was showed positive significance about four factors - perceived quality, reliability, authenticity and security on the customer satisfaction by the multiple regression analysis. Secondly, The effect of GIAP on the customer's revisit intention was showed positive significance about four factors - perceived quality, reliability, authenticity and security on the customer's revisit intention by the multiple regression analysis. Thirdly, the effect of the customer satisfaction on the customer's revisit intention was showed positive significance by the simple regression analysis. This study focused on medium level-cost Korean-pop restaurant so as to investigate general popular's recognition about the GIAP and intended to figure out their revisit intention. Therefore, the results are useful for increasing the food-service strategy system. Informations about the GIAP in restaurants can be credible to the restaurant customers.

• Journal of the Korean Society of Safety
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• v.33 no.1
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• pp.148-161
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• 2018

A traffic fatality by young people marked average annual decrease of 4.5% since 2011. Meanwhile, a traffic fatality by senior over 65 years old marked average annual increase of 7.9% for the last five years which means that the annual increase of traffic fatality by senior will be a serious problem. This study started questioning that senior drivers over 65 years old did not retain the same causal factor of fatal traffic accidents and thus extensively analyzed a risk of it by age group quantitatively, dividing the senior driver group into the early, middle and latter stages. Depending on the aging level, the risk of traffic fatality showed a wide difference in seven different types of traffic accidents generally, and happened to increase with latter and middle parts of the senior driver more than the early part. Therefore, this study proposes four policy suggestions: 1) The senior driver need to be offered customized driving educations and the improvement of road environment is also recommended. 2) Political assistance is needed to support and guide a safety related technology installation for the new or existing car. 3) Renewal of driving license and an aptitude test(physical examination, cognitive test) for drivers over 75 years old should take in a less than 3 years and an additional road test is needed as occasion demands. 4) Like the United States and Europe, development and extension of customized treatment guidebook for medical teams who examine senior drivers is needed and establishment of education and administration system that a supervisor of driving license renewal can impose safety restriction and American anonymity reporting system is considered to institutionalize in the medium to longer term.

• Preventive Nutrition and Food Science
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• v.22 no.2
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• pp.131-137
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• 2017

Maximum production of isoquercetin and quercetin simultaneously from rutin by subcritical water hydrolysis (SWH) was optimized using the response surface methodology. Hydrolysis parameters such as temperature, time, and $CO_2$ pressure were selected as independent variables, and isoquercetin and quercetin yields were selected as dependent variables. The regression models of the yield of isoquercetin and quercetin were valid due to the high F-value and low P-value. Furthermore, the high regression coefficient indicated that the polynomial model equation provides a good approximation of experimental results. In maximum production of isoquercetin from rutin, the hydrolysis temperature was the major factor, and the temperature or time can be lower if the $CO_2$ pressure was increased high enough, thereby preventing the degradation of isoquercetin into quercetin. The yield of quercetin was considerably influenced by temperature instead of time and $CO_2$ pressure. The optimal condition for maximum production of isoquercetin and quercetin simultaneously was temperature of $171.4^{\circ}C$, time of 10.0 min, and $CO_2$ pressure of 11.0 MPa, where the predicted maximum yields of isoquercetin and quercetin were 13.7% and 53.3%, respectively. Hydrolysis temperature, time, and $CO_2$ pressure for maximum production of isoquercetin were lower than those of quercetin. Thermal degradation products such as protocatechuic acid and 2,5-dihydroxyacetophenone were observed due to pyrolysis at high temperature. It was concluded that rutin can be easily converted into isoquercetin and quercetin by SWH under $CO_2$ pressure, and this result can be applied for SWH of rutin-rich foodstuffs.

• Earthquakes and Structures
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• v.11 no.5
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• pp.741-777
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• 2016

A simplified approach of assessing torsionally balanced (TB) and torsionally unbalanced (TU) low-medium rise buildings of up to 30 m in height is presented in this paper for regions of low-to-moderate seismicity. The Generalised Force Method of Analysis for TB buildings which is illustrated in the early part of the paper involves calculation of the deflection profile of the building in a 2D analysis in order that a capacity diagram can be constructed to intercept with the acceleration-displacement response spectrum diagram representing seismic actions. This approach of calculation on the planar model of a building which involves applying lateral forces to the building (waiving away the need of a dynamic analysis and yet obtaining similar results) has been adapted for determining the deflection behaviour of a TU building in the later part of the paper. Another key original contribution to knowledge is taking into account the strong dependence of the torsional response behaviour of the building on the periodic properties of the applied excitations in relation to the natural periods of vibration of the building. Many of the trends presented are not reflected in provisions of major codes of practices for the seismic design of buildings. The deflection behaviour of the building in response to displacement controlled (DC) excitations is in stark contrast to behaviour in acceleration controlled (AC), or velocity controlled (VC), conditions, and is much easier to generalise. Although DC conditions are rare with buildings not exceeding 30 m in height displacement estimates based on such conditions can be taken as upper bound estimates in order that a conservative prediction of the displacement profile at the edge of a TU building can be obtained conveniently by the use of a constant amplification factor to scale results from planar analysis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.4
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• pp.305-311
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• 2005

Shotcrete adhesive strength in large section tunnels in jointed rock masses plays an important role in preventing rock block from falling and shotcrete debonding due to blasting vibration. Nevertheless, it has not been considered as a major factor such as shotcrete compressive strength in design and construction. For this reason, the purpose of this study is to analyze the effect on shotcrete adhesive strength for large-sectioned tunnels. First, the parametric study using numerical model similar to Holmgren's punch-loaded test was executed for various range of adhesive strength. It shows that the shotcrete bearing capacity is linearly proportioned to the adhesive strength between shotcrete layer and blocks. And then, distinct element analysis of a jointed rock tunnel for an adhesive strength of 1 MPa and a conventional fully-bonded condition between the shotcrete layer and the excavation face was compared in order to evaluate the effect of the shotcrete adhesive strength.

• Geomechanics and Engineering
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• v.20 no.1
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• pp.43-54
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• 2020

The limit analysis and response surfaces method were combined to investigate the reliability of pressurized tunnel faces subjected to seismic force. The quasi-static method was utilized to introduce seismic force into the tunnel face. A 3D horn failure mechanism of pressurized tunnel faces subjected to seismic force was constructed. The collapse pressure of pressurized tunnel faces was solved by the kinematical approach. The limit state equation of pressurized tunnel faces was obtained according to the collapse pressure and support pressure. And then a reliability model of pressurized tunnel faces was established. The feasibility and superiority of the response surfaces method was verified by comparing with the Monte Carlo method. The influence of the mean of soil parameters and support pressure, variation coefficients, distribution type and correlation of c-φ on the reliability of pressurized tunnel faces was discussed. The reasonable safety factor and support pressure required by pressurized tunnel faces to satisfy 3 safety levels were presented. In addition, the effects of horizontal seismic force, vertical seismic force and correlation of k_h-k_v on the reliability of pressurized tunnel faces were also performed. The method of this work can give a new idea for anti-seismic design of pressurized tunnel faces.