• Journal of the Korean Institute of Gas
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• v.24 no.2
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• pp.22-28
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• 2020

In this study, quantitative risk assessment was carried out for city gas high-pressure pipelines crossing through urban rivers. The risk assessment was performed based on actual city gas properties, traffic volume and population and weather data in the worst case scenario conditions. The results confirmed that the social and individual risks were located in conditionally acceptable areas. This can be judged to be safer considering that the risk mitigation effect of protecting the pipes or installing them in the protective structure at the time of the construction of the river buried pipe is not reflected in the result of the risk assessment. Also, SAFETI v8.22 was used to analyze the effects of wind speed and pasquil stability on the accident damage and dispersion distances caused by radiation. As a result of the risk assessment, the safety of the pipelines has been secured to date, but suggests ways to improve safety by preventing unexpected accidents including river bed changes through periodic inspections and monitoring.

• Journal of Korea Port Economic Association
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• v.25 no.4
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• pp.21-44
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• 2009

This study aims to understand the conditions for using logistics outsourcing of Korean enterprises, present existing problems, examine factors affecting utility, and analyze the pattern of logistics outsourcing based on contract term, and to ultimately contribute to enhancing competitiveness of logistics enterprises. Through the literature survey 8 factors were identified as three broad factors of corporate strategy, corporate characteristics, and environment. Factor analysis was conducted on the bases of 155 collected data among 400 distributions for 2 months from April to May in 2008. From the result of analysis, the implication and finding can be summarized into three aspects. Firstly, Korean companies value factors relative to corporate strategies as motivating factors for logistics outsourcing. Secondly, Korean companies consider logistics outsourcing depending on how to handle customers' demands and the severity of competition. Thirdly, it was found that product and organization characteristics are perceived as more important when contract term with logistics business is longer. The implications can be observed into two aspects. Firstly once the logistics outsourcing between manufacturers and logistics companies are determined, it was verified that mutual agreement, particular contracts and periodic communications can increase the outcome. Secondly the logistics outsourcing appeared to be different depending on the level of entering to foreign market and resulted in higher performance as well.

• Journal of the Korean Society for Railway
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• v.20 no.5
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• pp.649-657
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• 2017

In this study, fatigue testing was carried out for long-term use of rail according to track type. From S-N curves for 50%~0.01% failure probability, the fatigue life of the long-term use rail for each track type was derived using the weight probability analysis technique on the experimental data. Because the rails used in the fatigue test have different cumulative tonnages, the number of repetitions was modified by averaging the cumulative tonnage. In addition, the bending stresses of rail bottoms, considering rail surface irregularities, track support stiffnesses and train speeds, were evaluated using the predicted rail bending stresses derived from existing studies. As a result, for rail fatigue life evaluation, the fatigue life of rail on the ballast track was found to be more than 200 million tons higher than the standard value for rail replacement. Also, the fatigue life of rail on concrete track is more than 300 million tons higher than that on ballast track. The Haibach rule is adaptable for the fatigue life evaluation of rail for stress range under fatigue limit.

• Journal of dental hygiene science
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• v.10 no.5
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• pp.329-334
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• 2010

This study was performed to identify the relationship between scaling behaviors and knowledge about scaling and oral health belief of worker, and to provide baseline data for developing industry oral health policy. The survey had conducted self-administered questionnaires by 326 workers in Gyeongsan and Yeongcheon areas in Gyeongbuk province. Their scaling behaviors, knowledge and oral health belief were measured. The results were as follow; The average score of knowledge about scaling was 6.44. The average oral health belief was 2.72. In detail, 'usefulness' was 3.24 as the highest and 'seriousness' was 2.25 as the lowest. The periodic scaling and scaling cycle were associated with 'seriousness' and 'barrier' as positive correlation(p<.05, .01). On the other hand, they were associated with knowledge and 'usefulness' as negative correlation(p<.01). Meanwhile, scaling motive showed positive correlation with 'cue of action'(p<.01), showed negative correlation with knowledge(p<.01). In the correlation between knowledge about scaling and oral health belief, knowledge showed negative correlation with 'barrier'(p<.01) and showed positive correlation with 'usefulness'(p<.01). Finally, we need to advertise and manage the importance of scaling politically and makes people do the voluntary scaling in six-month intervals in order to keep the periodontal health of worker.

• The Journal of the Acoustical Society of Korea
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• v.34 no.1
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• pp.12-19
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• 2015

In this paper, temporal variations of acoustic transmission loss (TL) affected by internal tide are studied by computer simulation using oceanic data measured in the southern sea of Jeju Island in summer. Temperature was measured with depth (bottom depth are nearly 80 m) in two sites near Seogwipo coast every one hour for 25 hours during July 27 and 28, 2009. The periodic fluctuation of temperature due to the internal tide was observed and its vertical displacement was more than 10 m. In order to investigate temporal variation of TL by internal tide, acoustic propagation between two measurement sites (3.8 km distance) was simulated with a source depth of 10 m. TL variation for 1/3 octave band of 100 Hz center frequency highly coincided with tidal period but more complex variation with indistinct tidal period was observed for 1 kHz. Maximun standard deviation of TL variation was 4.2 dB for 100 Hz at 2.8 km distance from a source and it was 3.7 dB for 1 kHz. The tidal variation was also shown in detection range and its maximum variance was less than 1 km. These results imply that temporal variation of TL should be considered for acoustic researches at the southern sea of Jeju Island.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.9
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• pp.533-542
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• 2016

The periodic maintenance of bridges is necessary once they have been constructed and its cost depends on various factors, such as their condition, environmental conditions and so on. To make a decision support system, it is essential to establish a basic reconstruction cost model. In this study, a regression model is suggested for calculating the reconstruction cost for typical cases and influential factors, depending on the type of bridge and its components, by analyzing the basic bridge specifications based on the data of the Bridge Management System (BMS). The details for each case were estimated in consideration of the cost calculation variables. The details for each case were estimated in consideration of the cost calculation variables. The cost model for the new construction of the superstructure, substructure and foundation and the temporary bridge construction and demolition costs were drawn from the regression analysis of the estimation results of typical cases according to the cost calculation variables. The reconstruction costs for different types of bridge were obtained using the cost model and compared with those in the literature. The cost model developed herein is expected to be utilized effectively in maintenance decision making.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.38 no.3
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• pp.35-49
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• 2020

The purpose of this study is to provide the baseline data for conservation and management of the ecosystem of urban forest by surveying and analysing the vascular plants distributed in Hwangseong Park, Gyeongju-si. The results of the survey of vascular plants from April 2018 to May 2020 were summarized as 338 taxa including 78 families, 222 genera, 296 species, 5 subspecies, 18 varieties, 6 forms, 4 hybrids and 9 cultivars, and 110 taxa of planted species and 235 taxa of native species were identified. The representative planting species was Liriope muscari. The 7 taxa of rare plants and 5 taxa of Korean endemic plants were investigated. The specific plants by floristic region were totally 24 taxa, which were 1 taxa of grade V, 4 taxa of grade IV, 7 taxa of grade III, 4 taxa of grade II and 8 taxa of grade I. The 57 taxa of naturalized plants and 6 taxa of invasive alien plants were showed. In particular, Chionanthus retusus represent traditional landscape trees in Korea and have high ecological value. Therefore, the old trees of Chionanthus retusus will have to be managed by assigning a number for each individual. The invasive alien plants will need periodic control and development of programs that can work in conjunction with civic groups.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.47 no.2
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• pp.103-112
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• 2010

In sensor networks, because sensors are deployed in an unprotected environment, they are prone to be targets of compromise attack, If the number of compromised nodes increases considerably, the key management in the network is paralyzed. In particular, compromise of Cluster Heads (CHs) in clustered sensor networks is much more threatening than that of normalsensors. Recently, rekeying schemes which update the exposed keys using the keys unknown to the compromised nodes are emerging. However, they cause some security and efficiency problems such as single group key employment in a cluster, passive eviction of compromised nodes, and excessive communication and computation overhead. In this paper, we present a proactive rekeying scheme using renewals of duster organization for clustered sensor networks. In the proposed scheme, each sensor establishes individual keys with neighbors at network boot-up time, and these keys are employed for later transmissions between sensors and their CH. By the periodic cluster reorganization, the compromised nodes are expelled from network and the individual keys employed in a cluster are changed continuously. Besides, newly elected CHs securely agree a key with sink by informing their members to sink, without exchangingany keying materials. The simulation results shows that the proposed scheme remarkably improves the confidentiality and integrity of data in spite of the increase of compromised nodes. Also, they show that the proposed scheme exploits the precious energy resource more efficiently than SHELL.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.41 no.1
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• pp.73-83
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• 2015

Dendropanax morbifera Leveille (Araliaceae) is an endemic species growing in the south-western part of South Korea and has been used in folk medicine. However, the effects of Dendropanax morbifera Lev. on skin biology remain to be elucidated. In this study, we isolated 1-tetradecanol and ${\beta}$-sitosterol from the n-hexane fraction of Dendropanax mobifera Lev. and To investigate the whitening effect of the fraction, we tested the inhibition of tyrosinase activity of 1-tetradecanol. The results show that the inhibitory effect of the 1-tetradecanol was higher than water extract and n-hexane fraction. And 1-tetradecanol significantly reduced melanin contents of B16F10 cells compared to more than water extract and n-haxane fraction dose-dependantly without cell cytotoxicitiy (below $100{\mu}g/mL$). We also investigated the skin moisturizing effect using HR-1 hairless mice. The transepidermal water loss (TEWL) in the 1-tetradecanol treated group was significantly smaller than that in the other groups. To investigate the effect of the preventing hair loss by ${\beta}$-sitosterol, we observed HR-1 hairless mice through periodic growth feature. The results suggest that hair loss of mice by ${\beta}$-sitosterol was delayed and it's hair density showed the highest. These data provide evidence that Dendropanax morbifera Lev. may be a potent candidate for the improvement of both skin whitening, moisturizing and alopecia from the point of cosmetic industry view.

• Journal of Soil and Groundwater Environment
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• v.14 no.4
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• pp.15-22
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• 2009

The remediation efficiency for a large scale petroleum-contaminated site was evaluated by using the Engineered Land-farming system which was consists of the following parameters; moisture & nutrient injector data, blower system, HDPE sheet and sump system. To enhance the degradation ability in the early stage, main nutrients such as nitrogen (N) and phosphorus (P) were adjusted for the site condition. As a result of the periodic tilling process, the concentration of contaminated soil was decreased to 348 mg/kg, which was lower than 500 mg/kg (regal standards) while satisfying remediation Efficiency of 82% (the maximum concentration of 1,893 mg/kg). The appropriate temperature range for an active operation was investigated between $28.9{\sim}35.6^{\circ}C$. For the contaminated soils having different initial concentration, the TPH (Total Petroleum Hydrocarbons) concentration was decreased evenly along with the CFU (Colony Forming Unit), moisture content and contaminant concentration after 38days of gratifying the legal standards of under 500 mg/kg.