• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.6
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• pp.599-612
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• 2013

This study aims to investigate an economical efficiency of two excavation methods with respect to the room-and-pillar method for the underground space and conventional excavation method, i.e. 2-arch tunnelling method. For feasibility study, an excavation cost for both room-and-pillar method and 2-arch tunnelling method was estimated when the same space in operation was required. It was assumed that properties of reinforcements and rock were adopted from literatures. However, an excavation shape of the room-and-pillar method was assumed not to be the rectangular shape which is a general type in the room-and-pillar method but to be an arch shape in order to compare with the conventional excavation method (2-arch tunnelling) and to achieve the maximum bearing capacity of the structure during excavation. Consequently, the wider space in use or required and the better condition of rock we assumed, the more economical advantage we have in the room-and-pillar method than the 2-arch tunnelling method.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.3
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• pp.355-373
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• 2017

Tunnelling in urban areas, it is essential to understand existing structure-tunnel interactive behavior. Serviced structures in the city are supported by pile foundation, since they are certainly effected due to tunnelling. In this research, thus, pile load distribution and ground behavior due to tunnelling below grouped pile were investigated using laboratory model test. Grouped pile foundations were considered as 2, 3 row pile and offsets (between pile tip and tunnel crown: 0.5D, 1.0D and 1.5D for generalization to tunnel diameter, D means tunnel diameter). Soil in the tank for laboratory model test was formed by loose sand (relative density: Dr = 30%) and strain gauges were attached to the pile inner shaft to estimate distribution of axial force. Also, settlements of grouped pile and adjacent ground surface depending on the offsets were measured by LVDT and dial gauge, respectively. Tunnelling-induced deformation of underground was measured by close range photogrammetric technique. Numerical analysis was conducted to analyze and compare with results from laboratory model test and close range photogrammetry. For expression of tunnel excavation, the concept of volume loss was applied in this study, it was 1.5%. As a result from this study, far offset, the smaller reduction of pile axial load and was appeared trend of settlement was similar among them. Particulary, ratio of pile load and settlement reduction were larger when the offset is from 0.5D to 1.0D than from 1.0D to 1.5D.

• The Journal of the Korea Contents Association
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• v.18 no.4
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• pp.114-127
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• 2018

This study aimed to investigate the levels of Obstructive Sleep Apnea (OSA), health behavior and sleep quality and to examine the predictors of OSA in patients with ischemic cardio-cerebrovascular disease. 141 patients who were admitted to the vascular unit were recruited and surveyed using structured questionnaires. Saturation of Peripheral Oxygen (SpO2) was measured at three time points using a pulse oximeter. Data were analyzed using SPSS/WIN 20.0. The mean age of the subjects was $64.4{\pm}11.1$ years and 61% was men. The 21.3%(n=30) of the subjects were classified as high-risk for OSA by the cut point and 71.6%(n=101) had low sleep quality. OSA high-risk group showed significant difference in SpO2 in the middle of sleep (p=.006) and at the end of sleep (p=.004) compared to the low-risk group. Multiple logistic regression analysis showed that perceived frequent snoring, smoking, obesity, lack of exercise among health behavior were found as predicting factors on OSA. OSA or persistent snoring should be recognized as a cardiovascular risk factor in the cardiovascular nursing practice. In addition to early treatment of OSA, education and counseling should be provided to patients and their family for prevention of secondary recurrence.

• Journal of the Korean Society for Marine Environment & Energy
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• v.18 no.1
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• pp.22-28
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• 2015

The design on a riser in 1MW OTEC system is performed. The minimum diameter of the riser is decided depending on intake quantity of deep-sea water to supply an OTEC cycle. An applicable pipe material is selected from analyzing the properties of commercial pipes. The selected HDPE pipe with the low density and strength is reinforced with a lumped block attached at the end of and wire ropes along the riser. A lumped block, connected to a floating structure by wire ropes, with 25% and 50% weight of a GFRP riser is designed to be attached the end of a riser. The structural safety of the HDPE riser with wire rope supporting axial loads induced by a lumped block is analyzed under the harsh ocean environmental condition near Hawaii ocean with the numerical method. The final dimension of the riser and accessories is determined considering the economic point of view. The designed riser will be applicable to the construction of the 1 MW OTEC pilot plant.

• Journal of the Korean association of regional geographers
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• v.14 no.3
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• pp.254-268
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• 2008

Jang Sang-Hoon(장상훈) concluded that Dongyeo(東輿) seemed to be made between 1859 and 1866 but it was ahead of Cheonggudo(靑邱圖) in terms of the content and format. Accordingly he insisted that Cheonggudo was compiled based on the original version of Dongyeo which was supposed to be drawn between 1790 and 1834. This paper reappraised critically the previous researches and got several findings. Firstly, the changes of place names-4 places names were selected for the Jang Sang-Hoon's research and 2 were added in this paper-are reflected in the Yeodobiji(輿圖備志) and Dongyeo compiled by Choi Seonghwan(최성환) and Kim Jeongho(金正浩) between 1853 and 1856. Secondly, the sectioning format of Dongye shows some transitional character from the book style such as Cheonggudo to the folding style that was shown in Dongyeodo(東輿圖) and Daedongyeojido(大東輿地圖). Thirdly, the expression of the mountains in Dongyeo shares the same style which is shown in Dongyeodo and Daedongyejido. Fourth, Dongyeo contains the same information about old military bases and the castle locations in small local town centers that appear in Dongyeodo and Daedongyeojido but not in Cheonggudo and similar kinds of maps. In conclusion, Dongyeo and the original version of it are likely to be drawn by Kim Jeongho between 1853 and 1856 after Cheonggudo was made.

• Journal of the Korean Applied Science and Technology
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• v.35 no.3
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• pp.757-767
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• 2018

In the propane dehydrogenation reaction proceeding at high temperature, the main cause of deactivation of the catalyst is coke deposition and sintering. In order to investigate the catalysts for reducing such inactivation, we have investigated the applicability of $MgAl_2O_4$ as a carrier for the catalytic dehydrogenation reaction. $MgAl_2O_4$ was prepared by Alcohthermal method at calcination temperature of 800, 900, $1000^{\circ}C$, and $Pt-Sn/MgAl_2O_4$ catalyst was prepared by supporting Pt and Sn by co-impregnation method. The reaction temperature was conducted at a high temperature of 650, $600^{\circ}C$ to confirm the thermal stability. As a result of the reaction experiment, it was confirmed that the conversion rate and yield of propane dehydrogenation reaction test were higher than that of the carrier-applied catalyst having a carrier calcination temperature of 900 and $1000^{\circ}C$, when the carrier-applied catalyst having a calcination temperature of $800^{\circ}C$ was used, It was found that the yield was higher than that of $Pt-Sn/{\theta}-Al_2O_3$ at $650^{\circ}C$. TGA, BET, XRD, CO-chemisorption, and SEM-EDS analyzes were performed for characterization. $MgAl_2O_4-800^{\circ}C$ was correlated with the relationship between good yield, Pt dispersion and low deactivation rate.

• The Journal of the Korea Contents Association
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• v.20 no.5
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• pp.222-235
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• 2020

This study examines the poverty progress and its factors which drove the lives of the middle-aged men in Chokbang area. The observed examples are the retired government officials and the self-employed who have been classified as the ones in the economically-middle class but currently as the welfare recipients. According to the results of in-depth interview and observation, the poverty of the observed has undergone the progress of trigger, worsening, breakup, desperation and stabilizing stages. The poverty factors found in this study could be categorized into two factors; circumstantial factors(bankruptcy after IMF, debt guarantee for relatives) and inner factors(the participants' behavior and characteristics). The circumstantial factors worked mainly in the trigger stage and the inner factors contributed to worsening economic crisis and facilitating the progress. According to the result, this study suggests not only individual-scale measures such as encouragement of familial bond or medical treatment of the alcoholism but also social measures including proper regulation of shark loan and opportunity supply to exit from poverty.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.54-63
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• 2018

In this study, the stability and economic feasibility of a MSE (Mechanically stability earth) wall with a pre-cast concrete pacing panel was investigated for a standard section of highway. Based on the design criteria, the MSE walls of the panel type were designed considering the load conditions of the highway, such as the dead load of the concrete pavement, traffic load, and impact load of the barrier. The length of the ribbed metal strip was arranged at 0.9H according to the height of the MSE walls. Because the length of the reinforcement was set to 0.9H according to the height of the MSE wall, the external stability governed by the shape of the reinforced soil was not affected by the height increase. The factor of safety (FOS) for the bearing capacity was decreased drastically due to the increase in self-weight according to the height of the MSE wall. As a result of examining the internal stability according to the cohesive gravity method, the FOS of pullout was increased and the FOS of fracture was decreased. As the height of the MSEW wall increases, the horizontal earth pressure acting as an active force and the vertical earth pressure acting as a resistance force are increased together, so that the FOS of the pullout is increased. Because the long-term allowable tensile force of the ribbed metal strip is constant, the FOS of the fracture is decreased by only an increase in the horizontal earth pressure according to the height. The panel type MSE wall was more economical than the block type at all heights. Compared to the concrete retaining wall, it has excellent economic efficiency at a height of 5.0 m or more.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.672-680
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• 2018

The opening angle of the duct cap assembly during the operation of a refrigerator ice dispenser was evaluated by transient structural analysis, and an improved design to maximize the opening angle was obtained. The opening angle of the existing design was found to be 78% of the upper limit. Several design modifications were proposed and analyzed to examine the effects of the design factors on the opening angle. As a result of the design modifications, the opening angle was improved by changing the lever material to a material with a high elastic modulus, moving the position of the support to the motor side, or increasing the lever shaft diameter. Considering the manufacturing cost of the new design, the design modification changing only the lever material was found to be the best because it does not require a change in the structure of the ice dispenser case. In conclusion, the opening angle can be improved by up to 95% of the upper limit value if the lever material is changed to an aluminum alloy. The methods and results presented in this study were found to be of great help in designing the duct cap assembly structure to facilitate the discharge of ice.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.399-409
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• 2018

The mechanically stabilized earth wall (MSEW) of the IPM bridge is an important structure that constitutes the bridge, and supports the horizontal earth pressure and approach slab. Therefore, it is necessary to carefully analyze the settlement of MSEW of the IPM bridge. This study examined the settlement according to the height and ground stiffness on the MSEW on the IPM Bridge. According to the design guideline, the IPM Bridge (2016) was designed to have a height of 4.0 ~ 10.0m and the elastic settlement was calculated. The base area and the grounding pressure of the MSE wall increased linearly with the height, and the elastic settlement also increased linearly. In addition, the stiffness of the foundations satisfying the allowable settlement of the approach slab is a N value of 35 or more. The settlement of finite element analysis was estimated to be smaller than the elastic settlement, and the stiffness of the foundation ground satisfied the allowable settlement of the approach slab above N value of 20. Because the elastic settlement of the MSEW of the IPM Bridge was overestimated, it will be necessary to examine it carefully by finite element analysis.