• Journal of the Korea Institute of Building Construction
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• v.14 no.6
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• pp.639-645
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• 2014

For the construction materials, concrete, as the most widely used material, is focused on its improvement of performance. Although concrete has many advantages of easiness of handling, economical benefits, and high compressive strength, low tensile strength, brittleness and drying shrinkage are reported as the drawbacks of concrete. Hence, to solve these drawbacks of concrete, many research has conducted especially using fiber-reinforced concrete technology. Especially, HPFRCC which has high volume of fiber reinforcement was suggested as a solution of these drawbacks of normal concrete with increased ductility while it has the possibility of workability loss with fiber clumping which can cause low performance of concrete. Therefore, in this paper, optimized fiber combination with either or both metal and organic fibers is suggested to provide better performance of HPFRCC in tensile strength and ductility. As the results of experiment, better workability was achieved with 1 % of single fiber rather than multiple fibers combinations, espeically, short steel fiber showed the best workability result. Furthermore, in the case of organic fibers which showed higher air content than steel fibers, higher compressive strength was achieved while lower tensile and flexural strength were shown.

• Journal of Chest Surgery
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• v.39 no.1 s.258
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• pp.56-59
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• 2006

Background: Spontaneous pneumomediastinum (SPM) is a relatively rare and benign condition that generally occurs in young adults without any precipitating factor or disease. The purpose of this study was to assess whether more uncomforting diagnostic procedures are necessary and to establish standards in the diagnosis and treatment of spontaneous pneumomediastinum. Material and Method: A retrospective study was done on 18 patients from the hospitals of Hanyang University Seoul Hospital and Hanyang University Guri Hospital between February, 1997 and June, 2004. All patients had presence of mediastinal air without a pneumothorax and no evidence of trauma or barotrauma. Result: Among the 18 patients, the majority were male patients with only two female patients. Their mean age was 20.95 years old with standard deviation of 14.3 years. The most common complaints were chest pain, dyspnea, and coughing. Evaluation included simple chest roentgenogram in all patients, 10 patients had a chest tomographic scan, 10 patients had an esophagoscopic exam, 6 patients had a bronchofiberoscopic exam, and 3 patients had an esophagogram done. The mean hospital stay was 10.9 days. All patients were treated conservatively and in a follow-up of 1 $\∼$ 8 years only one recurrence was found. Conclusion: SPM is caused by alveolar rupture in the pulmonary interstitium leading to dissection of air towards the hilum and mediastinum. Although SPM is a self-limiting condition, evaluation should include chest roentgenogram and chest tomographic scans to rule out any other secondary condition. More aggressive evaluation seems unnecessary.

• Land and Housing Review
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• v.4 no.4
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• pp.417-424
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• 2013

The purpose of this study was to investigate the characteristics of the indoor air quality by season. The surveyed houses were 48 new apartment complex in 2012 across the country. The houses were carried out the bakeout before the test. The measuring method was "Indoor air quality testing standards process" and the measured items were formaldehyde, benzene, toluene, ethylbenzene, xylene, styrene average emissions. All the items were more emitting during the summer. From June to September the average concentration of formaldehyde emission was higher than other seasons. The average emissions of benzene concentrations in all seasons were released in small quantities. Average emissions of toluene and ethylbenzene concentration from April to August showed slightly higher emissions. Xylene and styrene concentration showed the highest emissions at April, but without large deviations throughout the year.

• Journal of Bio-Environment Control
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• v.27 no.3
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• pp.206-212
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• 2018

As many consumers prefer good quality food, farms have used various facilities to cultivate products for satisfying their desires. Among them, the most representative facilities are plastic and glass multi-span greenhouse. The height of both plastic greenhouse and glass greenhouse is around three meters high in Korea. As a result, the crop productivity is limited. The solution is to increase the height of the greenhouses to improve the greenhouses' environment. The device for raising columns consists of a stop device, a pneumatic cylinder, and a vertical member. Pneumatic cylinders were designed with a diameter of 160 mm and a stroke length of 50 mm, taking into consideration the safety factor of 1.5. In addition, the air flow was controlled by nozzle to achieve a time of less than 30 seconds per stroke. It was calculated that $21.5L{\cdot}min^{-1}$ of air was needed to complete in less than 30 seconds. Accordingly, the diameter of the nozzle is designed to be 0.5 mm. When the pressure was 0.9 MPa, the average raising force was 13,805N, which was close to the calculated value of 15,612N. The field test results show that any inconsistency in the row columns was not generated. and that it is considered applicable to the actual glass and plastic greenhouses.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.5
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• pp.17-25
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• 2016

In this study, the air quality of underground and overground railway stations was evaluated focusing on the degree of influence of the outside air quality. The measured components were particulate matter ($PM_{10}$), carbon dioxide ($CO_2$), carbon monoxide (CO), nitrogen dioxide ($NO_2$), formaldehyde (HCHO), ozone ($O_3$), total airborne bacteria (TAB), total volatile organic carbon (TVOC), and Radon (Rn), which are included in the maintenance standards and recommended standards of the Indoor Air Quality Management Act. Also, the indoor/outdoor concentration ratios of $PM_{10}$, $NO_2$, and $O_3$ were calculated to estimate the influence of the outdoor air quality. The concentrations of $PM_{10}$ HCHO, TVOC, $NO_2$, and Rn in the underground stations were found to be higher than those in the overground stations. These results indicate that the (present) generation of contaminants are caused by the indoor source of the underground station. The ozone concentration of the overground stations was higher than that of the underground stations, which indicates that the outdoor ozone concentration influenced that of the overground stations directly. Thus, methods of improving the IAQ should take into consideration the types of contamination.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.609-619
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• 2018

This study was carried out at a local limestone mine to analyze the ventilation efficiency of the shaft equipped with a main fan. The results show that its ventilation efficiency is clearly verified for the natural as well as the mechanical ventilation. The airflow rate of $11.7m^3/s$ was induced by the natural ventilation force and the maximum quantity is almost same as the airflow rate estimated by monitoring the average temperatures in the upcast and downcast air columns. Meanwhile, the airflow rate exhausted by the main fan through the shaft was $20.3{\sim}24.8m^3/s$; variation of the quantity was caused by the upward shift of the mine ventilation characteristic curve due to the frequent movement of the equipment. This indicates efforts are required to reduce the ventilation resistance and raise the quantity supplied by the main fan. The turbulent diffusion coefficients along the 1912 m long airway from the portal to the shaft bottom was estimated to be $15m^2/s$ and $18m^2/s$. Since these higher coefficients imply that contaminants will be dispersed at a faster velocity than the airflow, prompt exhaust method should be planned for the effective air quality control. The ventilation shaft and main fan are definitely what local limestone mines inevitably need for better working environment and sustainable development.

• Journal of Environmental Impact Assessment
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• v.30 no.4
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• pp.187-202
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• 2021

This study examined the effectiveness of wind corridor construction by analyzing the thermal environment, cold air generation, ventilation, and geographical characteristics to improve urban thermal environment and establish the basis for specialized strategy in Changwon-si, Gyeongsangnam-do. Using spatial analysis and remote sensing techniques, surface temperature, land cover and land use, wind field, and slope were measured and through this, a wind corridor analysis model was constructed. As a result of the analysis as of 2020, Changwon-si generally has land cover characteristics that are advantageous for the generation of cold air, but the temperature in most urban areas is the highest, and the temperature in areas such as north Changwon area, Jinbukmyeon, Ung-dong, and Ungcheon-dong are relatively high. There was a typical trend of high average wind speed in mountain regions and low average wind speed in urban areas. Accordingly, the north Changwon area, the former Changwon downtown area, the Hogye-ri and Pyeongseong-ri areas, and the Changpo Bay area are derived as vulnerable areas to thermal environment, and various measures to reduce temperature and improve air quality that the inflow of cold air into the area considering the characteristics of each area and securing wind ventilation between the surrounding mountains, reservoirs, and park areas were proposed.

• Journal of the Korean Society of Floral Art and Design
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• no.44
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• pp.3-31
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• 2021

To verify the types of effects that plants have in our general living conditions, I examined an air quality in living rooms of the three, 129.78m² size, apartments that were with and without plants. and the findings of the study were as addressed below. 1) Experiments showed no statistically significant differences in Case A. However, in Case B and Case C, the standard deviation of PM10, PM2.5 and PM 1.0 verified that each had statistically significant (p<.01) differences. 2) It is believed that the effect of reducing particle matters due to the installation of plants in the indoor space is to vary significantly depending on the indoor environmental conditions, the cleanliness of the room, and the amount of furniture and may also differ depending on the daily dietary cooking method. In addition, it is believed that the planterior will not only reduce indoor fine dust, but also reduce the psychological comfort and eye fatigue of the residents. Nevertheless, supplementary research is needed. 3) In the planterior design for reducing indoor particle matters, various measures were examined. Among them, the vertical wall design method was tested and suggested through empirical experiments. In addition, maintenance methods were proposed depending on the type of indoor plant.

• Journal of Convergence for Information Technology
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• v.12 no.2
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• pp.134-141
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• 2022

To improve the performance of aluminum-air batteries, it is very important to understand the effect of electrolytes on the electrochemical properties of electrodes. In this study, the effects of electrolyte cations on the electrochemical redox reactions proceeding at the negative and positive electrodes were investigated using electrolytes having the same anion but different cations such as NaCl, LiCl, CaCl₂, and ZnCl₂. It was confirmed by discharge test, scanning electron microscopy and X-ray diffraction analysis that electrolyte cations affect the discharge potential and specific capacity of the electrode. Precipitates were formed on the surface of the positive electrode by Ca²⁺ and Zn²⁺ ions, resulting in degradation of the performance of the positive electrode. In addition, Ca²⁺ ions passivated the negative electrode and accelerated the performance degradation. This suggests that the positive ions of the electrolyte have different effects on the electrochemical performance of the positive and negative electrodes.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.4
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• pp.395-401
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• 2009

One of the key design factors for the ventilation and safety system at extra long tunnel is the airflow velocity induced by the natural ventilation force. Despite of the importance, it has not been widely studied due to the complicated influencing variables and the relationship among them is difficult to quantify. At this moment none of the countries in the world defines its specific value on verified ground. It is also the case in Korea. The recent worldwide disasters by tunnel fires and demands for better air quality inside tunnel by users require the optimization of the tunnel ventilation system. This indicates why the natural ventilation force is necessary to be thoroughly studied. This paper aims at predicting the natural ventilation force at a 11 km-long tunnel which is in the stage of detailed design and will be the longest vehicle tunnel in Korea. The concept of barometric barrier which can provide the maximum possible natural ventilation force generated by the topographic effect on the external wind is applied to estimate the effect of wind pressure and the chimney effect caused by the in and outside temperature difference is also analyzed.