• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.5
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• pp.3518-3524
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• 2015

Spatial and time variation of the precipitation in Korea is high, therefore, more than 2/3 of the annual precipitation is concentrated during the rainy season. Climate change also causes the intensive rainfall in the area of dense population, thus the occurrence frequency of the heavy flood in the impervious area has been increased. Therefore, the structural food mitigation measures such as the construction of the higher design frequency stormwater pipes, pumping stations, and/or detention ponds. The flood bypass tunnel or retention storage is also one of the efficient structures to mitigate flood damage in the urban area. However, the economic feasibility has been controversial because the flood bypass tunnel might be used once or twice a year. To solve the problem, the multi-functional tunnel for the urban traffic and flooding bypass has been considered. In this study, the design criteria of the road and water tunnel has been analysed and the composite design criteria is proposed for the multi-functional tunnel which is expected to be constructed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.10
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• pp.403-411
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• 2016

Recently, the number of occurrences of inundation and the severity of flood damage has increased rapidly as the frequency of localized heavy rainfall and the ratio of impervious area increased in urban areas. Most local governments focus on employing structural measures (e.g., the construction of detention reservoirs/pump stations, rehabilitation of drainage and sewer pipes) to prevent urban inundation. On the other hand, the effectiveness of implementing such structural measures is being dimished because there are already many inundation prevention facilities. The limitation of structural measures can be overcoming by employing non-structure measures, such as flood alerts and the operation of drainage facilities. This study suggests the pump operation rule (i.e., suggesting pump stop level) for a new detention reservoir operating method, which triggers the operation of a pump based on the water level at the monitoring node in urban drainage system. In the new reservoir operation, a total of 48 rainfall events are generated by the Huff distribution for determining the proper pump stop level. First, the generated rainfall events are distributed as frequencies, quartiles, and durations. The averaged system resilience value was determined to range from 1.2 m to 1.5 m is based on the rainfall-runoff simulation with rainfall generated by the Huff distribution. In this range, 1.2 m was identified considering the safety factor of 1.25 by the Standard on sewer facilities in 2011.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.143-150
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• 2011

Energy loss at manholes, often exceeding friction loss of pipes under surcharged flow, is considered as one of the major causes of inundation in urban area. Therefore, it is important to analyze the head losses at manholes, especially in case of surcharged flow. The stream characteristics were analyzed and head loss coefficients were estimated by using the computational fluid dynamics(CFD) model, FLUENT 6.3, at surcharged square manhole in this study. The CFD model was carefully assessed by comparing simulated results with the experimental ones. The study results indicate that there was good agreement between simulation model and experiment. The CFD model was proved to be capable of estimating the head loss coefficients at surcharged manholes. The head loss coefficients with variation of the ratio of manhole width(B) to inflow pipe diameter(d) and variation of the drop height at surcharged square manhole with a straight-path through were calculated using FLUENT 6.3. As the ratio of B/d increases, head loss coefficient increases. The depth and head loss coefficient at manhole were gradually increased when the drop height was more than 5cm. Therefore, the CFD model(Fluent 6.3) might be used as a tool to simulate the water depth, energy losses, and velocity distribution at surcharged square manhole.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.56-66
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• 2021

In this study, a waste heat recovery system was devised and the performances of components incorporated to recover the heat generated during the processing of aerobic liquid-composting in a livestock manure treatment facility were analyzed. In addition, the availability of recovered heat was confirmed. The heat generated by liquid fermentation in the livestock manure treatment facility was also checked. Experimental temperatures were set at 35, 40, and 45 ℃ based on considerations of the uniformity of aerobic liquid-composting fermentation tank temperature and its operating range (34.5 ~ 43.9 ℃). Recovered heat energies from the combined heat exchanger, which consisted of PE and STS pipes, were 53.5, 65.6, 74.4 MJ/h, The heat pump of capacity 5 RT was heated at 95.6, 96.1, 98.9 MJ/h and the heating COPs of the pump were 4.53, 4.62, and 4.65, respectively. The maximum hot water production capacity of the heat exchanger assuming a fermentation tank temperature of 45 ℃ confirmed an energy supply of 56 360 kcal/day. The heating capacity of the FCU linked to the heat storage tank was 20.8 MJ/h, and the energy utilization efficiency was 96.1%. When livestock manure was dried using the FCU, it was confirmed that the initial function rate was reduced by 50.5 to 45.8 % after drying.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.513-519
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• 2019

Typically, contaminated sediments cause clogging of the drain pipe, which increases the residual water pressure in the drain pipe; this study constructed a system for improving drainage efficiency of tunnels by reducing physical and chemical obstructions through ultrasonic energy generated by a PVDF film. The developed hybrid drainage system utilized a PVDF material film fused with an existing drainage tunnel and maintenance system resulting in the ability to initialize the reverse piezoelectric effect, which was evaluated through an on site application. In order to investigate the maintenance performance of the tunnel drainage system, contaminated sediments were simulated in a drainage pipe to test the effect of ultrasonic conditions on drainage efficiency in the laboratory. As a result of applying the developed portable equipment, the ultrasonic energy was generated for about 20 minutes resulting in a reduction of 74.62% of the contaminated sediments and improving drainage efficiency. From the tunnel, acoustic pressure measurements were taken to calculate the response rate while taking into account the laboratory results. In addition, PVDF film was attached to the transverse and longitudinal side of the drainage pipes where contaminated sediments occur most often in the field tunnel. these calculations show contaminant removal was 90% effective.

• Journal of Korean Tunnelling and Underground Space Association
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• v.20 no.6
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• pp.1073-1090
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• 2018

Since the domestic utility tunnels were built mainly in the development project of the new city, they are all in the form of cut-and-cover box tunnel. But, in the case of overseas construction of utility tunnels for existing urban areas, the bored tunnel types are mainly adopted. It is reasonable to install bored tunnels in a downtown area because it is difficult to block the roads or install bypass roads due to heavy traffic and civil complaints. In order to activate the utility tunnels in bored type, it is necessary to secure optimized cross-sectional design technology considering the optimal supplying capacity and mutual influencing factors (Thermal Interference, electrolytic corrosion, efficiency of the maintenance, etc.) of utilities (power cables, telecommunication cables, water pipes, etc.). The optimal cross-section design method for bored utility tunnels is ultimately to derive the optimal arrangement technique for the utilities. In order to develop the design methods, firstly, the cases of tunnel cross-section (Shield TBM, Conventional Tunneling) in overseas shall be investigated to analyze the characteristics of the installation of utilities in the section and installation of auxiliary facilities, It is necessary to sort out and analyze the criteria related to the inner cross-section design (arrangement) presented in the standards and guidelines.

• Journal of the Korean Institute of Gas
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• v.22 no.6
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• pp.76-89
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• 2018

The distribution of the combined heat and power system is active as a solution to the instability of energy supply and environmental pollution caused by continuous industrial development. In Korea, the safety standards for combined heat and power system using a gas engine are insufficient therefore the study on this is needed. In this study, the safety performance and structural/material assessment items of domestic and international standards applied to the combined heat and power system were analyzed to carry out a standardization study on safety performance applicable to 20 kW gas engine combined heat and power system. In addition, the safety performance assessment (plan) of the gas engine combined heat and power system was derived by performing risk analysis and risk assessment using HAZOP. Assessment items include engine ignition systems related to safety performance, piping tight performance, watering and temperature rise performance, combustion performance, electrical efficiency, thermal efficiency, overall efficiency and humidity performance. Gas and water pipes, gas control and shut-off valves, durability, heat resistance, and cold resistance of metal or non-metallic materials related to the structure and materials of the gas engine combined heat and power systems.

• Tunnel and Underground Space
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• v.28 no.6
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• pp.596-608
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• 2018

As urban infrastructure is aging, the possibility of accidents due to the failures or breakdowns of infrastructure increases. Especially, aging underground infrastructures like sewer pipes, waterworks, and subway have a potential to cause an urban ground sink. Urban ground sink is defined just as a local and erratic collapse occurred by underground cavity due to soil erosion or soil loss, which is separated from a sinkhole in soluble bedrock such as limestone. The conventional measurements such as differential settlement gauge, inclinometer or earth pressure gauge have a shortcoming just to provide point measurements with short coverage. Therefore, these methods are not adequate for monitoring of an erratic subsidence caused by underground cavity due to soil erosion or soil loss which occurring at unspecified time and location. Therefore, an alternative technology is required to detect a change of underground physical condition in real time. In this study, the feasibility of a novel magnetic resonance based monitoring method is investigated through laboratory tests, where the changes of path loss (S21) were measured under various testing conditions: media including air, water, and soil, resonant frequency, impedance, and distances between transmitter (TX) and receiver (RX). Theoretically, the transfer characteristic of magnetic field is known to be independent of the density of the medium. However, the results of the test showed the meaningful differences in the path loss (S21) under the different conditions of medium. And it is found that the reflection coefficient showed the more distinct differences over the testing conditions than the path loss. In particular, input reflection coefficient (S11) is more distinguishable than output reflection coefficient (S22).

• Journal of Conservation Science
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• v.34 no.6
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• pp.459-470
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• 2018

Cellulose nitrates were used for folklore artifacts(ornamental beads and pipes in hatstrings, frames of eyeglasses, ornamental eyeglass cases, headband ornaments, and jeogori buttons) between the 19th and 20th centuries; however, they are susceptible to cracking, crazing, embrittlement, and crumbling due to deterioration. To consolidate and adhere deteriorated cellulose nitrate folklore artifacts, water-soluble acrylic emulsion adhesives were investigated. For consolidation, Plextol D 498, which has the lowest viscosity in low concentrations, was used. In adhesive films whose glass transition temperature(Tg) is lower than room temperature, the tensile stress and modulus decreased and the strain increased; therefore, the flexibility was high. The Plextol D 498 and Plextol D 498 and Dispersion K 52 films maintained their adhesiveness and flexibility after artificial-sunlight-accelerated ageing, and Plextol D 498 and Dispersion K 52 films hardly caused yellowing. Plextol D 498 was the most stable for accelerating ageing. A low concentration of Plextol D 498 emulsion resulted in the best permeability on the surface of cellulose nitrate, compared with other acrylic emulsions. To prevent ornamental hatstrings from cracking, crazing, embrittlement, and crumbling, a Plextol D 498 emulsion was used. After applying low concentrations(1%, 3%) of the emulsion to consolidate the fragments and high concentration to adhere the fragments, the ornamental hatstrings were protected from crumbling by deterioration, and their fragments were well-adhered. To preserve it from deterioration by oxygen and humidity, the treated ornament was sealed with an oxygen-barrier film using a low-humidity oxygen scavenger.

• Ecology and Resilient Infrastructure
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• v.8 no.1
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• pp.44-53
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• 2021

The flood prevention capacity of drainage facilities in urban areas has weakened because of the increase in impervious surface areas downtown owing to rapid urbanization as well as localized heavy rains caused by climate change. Detention can be installed in trunk sewers and linked to existing drainage facilities for the efficient drainage of runoff in various urban areas with increasing stormwater discharge and changing runoff patterns. In this study, the concept of detention in trunk sewers, which are storage facilities linked to existing sewer pipes, was applied. By selecting a virtual watershed with a different watershed shape, the relationship between the characteristic factors of detention in the trunk sewer and the design parameters was analyzed. The effect of reducing stormwater runoff according to the installation location and capacity of the reservoir was examined. The relationship between the installation location and the capacity of the detention trunk sewer in the Dowon district of the city of Yeosu, South Korea was verified. The effects of the existing water runoff reduction facility and the detention trunk sewer were also compared and analyzed. As a result of analyzing the effects of reducing internal inundation, it was found that the inundation area decreased by approximately 66.5% depending on the installation location of the detention trunk sewer. The detention trunk sewer proposed in this paper could effectively reduce internal inundation in urban areas.