• Journal of Korea Water Resources Association
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• v.43 no.2
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• pp.131-138
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• 2010

Due to the increased water demand and severe drought as an effect of the global warming, the effluent from wastewater treatment plants becomes considered as an alternative water source to supply agricultural, industrial, and public (gardening) water demand. The effluent from the wastewater treatment plant is a sustainable water source because of its good quality and stable amount of water discharge. In this study, the water reuse system was developed to minimize total construction cost to cope with the uncertain water demand in future using two-stage stochastic linear programming with binary variables. The pipes in the water reuse network were constructed in two stages of which in the first stage, the water demands of users are assumed to be known, while the water demands in the second stage have uncertainty in the predicted value. However, the water reuse system has to be designed now when the future water demands are not known precisely. Therefore, the construction of a pipe parallel with the existing one was allowed to meet the increased water demands in the second stage. As a result, the trade-off of construction costs between a pipe with large diameter and two pipes having small diameters was evaluated and the optimal solution was found. Three scenarios for the future water demand were selected and a hypothetical water reuse network considering the uncertainties was optimized. The results provide the information about the economies of scale in the water reuse network and the long range water supply plan.

• Journal of the Korean Institute of Gas
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• v.16 no.3
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• pp.22-28
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• 2012

For a methanol separation column of the BPA (Bisphenol A) plant, HAZOP (hazard and operability) assessment was performed and damage ranges were predicted from the accident scenarios for the fire and the explosion. As a result, the damage range of the jet fire was 20 m in the case of rupture of the discharge pipe (50 mm diameter) of safety valve, and that of the flash fire was 267 m in the case of catastrophic rupture. Also, the damage ranges of the unconfined vapor cloud explosion (UVCE) for the rupture of the discharge pipe and for the catastrophic rupture were 22 m and 542 m, respectively. For the worst case of release scenarios, safety measures were suggested as follows: the pressure instruments, which can detect abnormal rise of the internal pressure in the methanol separation column, should be installed by the 2 out of 3 voting method in the top section of the column. Through the detection, the instruments should simultaneously shut down the control and the emergency shut-off valves.

• Resources Recycling
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• v.9 no.4
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• pp.28-36
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• 2000

This study describes to analyze the characteristics for separation and recovery of both the dried particles and the purified solvent from the waste solvent through the vaporization process by the continuous and instantaneous vacuum drying system. The vacuum drying system for the waste solvents recovery consists of a feeding pump, a double pipe heat exchanger, a vacuum spray chamber, and a condenser. The vacuum drying system heats the waste solvent to the vapor in the double pipe heat exchanger and the expanded vapor is sprayed at the end of the tube. The vaporized solvent in the condenser are recovered. The particles in the waste solvent are separated and dried from the vapor in the vacuum spray chamber. Performance evaluation of the vacuum drying system was conducted using the mixture of the dried pigment particles and benzene or alkylbenzene as test samples. For the mixture of 10 wt% pigment particles an 90% benzene, the recovery efficiency of benzene was 88% with the purity of 99% and the recovery efficiency of dried particles was 94% with the moisture of 1.1 wt%. The size of pigment particles was decreased from $6.5\mu\textrm{m}$ to $5.6\mu\textrm{m}$ in diameter due to high speed spraying and dispersion in the vacuum drying system during drying process. Therefore, the vacuum drying system showed to be an effective method for separating particles and solvent in the waste solvent.

• Journal of the Korean Society of Propulsion Engineers
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• v.25 no.1
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• pp.1-11
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• 2021

POGO is a dynamic axial instability phenomenon that occurs in liquid-propelled rockets. As the natural frequencies of the fuselage and those of the propellant supply system become closer, the entire system will become unstable. To predict POGO, the propellant (oxidant and fuel) tank in the first stage is modeled as a shell element, and the remaining components, the engine and the upper part, are modeled as mass-spring, and structural analysis is performed. The transmission line model is used to predict the pressure and flow perturbation of the propellant supply system. In this paper, the closed-loop transfer function is constructed by integrating the fuselage structure and fluid modeling as described above. The pogo suppressor consists of a branch pipe and an accumulator that absorbs pressure fluctuations in a passive manner and is located in the middle of the propellant supply system. The design parameters for its design optimization to suppress the decay phenomenon are set as the diameter, length of the branch pipe, and accumulator. Multiple-objective function optimization is performed by setting the energy minimization of the closed loop transfer function in terms of to the mass of the pogo suppressor and that of the propellant as the objective function.

• Journal of the Society of Disaster Information
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• v.18 no.3
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• pp.542-549
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• 2022

Purpose: Pipes are widely used as applied devices in many industrial fields such as machinery, electronics, electricity, and plants, and are also widely used in safety-related fields such as firefighting and chemistry. With the diversification of products, the importance of technology in the piping field is also increasing. In particular, when changing the existing copper pipe to stainless steel, it is necessary to evaluate safety and flow characteristics through structural analysis or flow analysis. Method: This study investigated the structural stability of the 6.35 and 15.88 socket models, which are integrated insert type connectors developed by a company, using FEM. For structural analysis, HyperMesh as pre-processor, HYPER VIEW as post-processor, and LS-DYNA as solver were used. Result: In the case of 6.35 socket, the maximum stresses at hook, holder and hinge were 95.02MPa, 19.59MPa and 44.01MPa, respectively, and in case of 15.88 socket, it was 127.7 MPa, 40.09MPa and 45.23MPa, respectively. Conclusion: Comparing the stress distribution of the two socket models, the stress in the 15.88 socket, which has a relatively large outer diameter, appears to be large overall, but it is significantly lower than the yield stress of each material, indicating that there is no problem in structural safety in both models.

• Journal of the Korean Geotechnical Society
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• v.39 no.7
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• pp.69-76
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• 2023

Cavity causes settlement and its remediation after an accident results in significant time and economic losses. This study aims to experimentally evaluate the prospect of using infrared camera to detect and measure underground subsidence. Emissivity is necessary to detect the energy emitted from an object and accurately assess temperature using an infrared camera. The emissivity in laboratory tests is fixed to evaluate a reasonable distance between the infrared camera and the object, and temperature values are assessed at various distances. In field experiments, the cavity of the field experiment is simulated using a PVC pipe with a diameter of 5 cm, artificially buried at depths of 5 and 25 cm from the surface. The infrared camera measurements are taken from 4 PM to 3 PM of the next day (a total of 23 h). The analysis included the time-series temperature distribution and the cooling rate index assessment, which represents the temperature change rate per unit of time. The results showed that various temperature trends are observed depending on the location of the subsidence. This study demonstrates that the infrared camera can be used to assess the condition of the subsurface.

• Geotechnical Engineering
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• v.7 no.3
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• pp.51-64
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• 1991

The reliable estimation of pile bearing capacity is essential for the improvement of the re- liability and the cost-effectiveness of the design. There have been numerous pile bearing capacity prediction methods proposed up to now, however, execpt for the estimation made from the result of the pile loading test, not one method is appropriate for the reliable prediction. Due to the considerable time and expenses required to carry out the pile loading test, the test has seldom been utilized. The development of Simple Pile Loading Test(SPLT) which utilizes the pile skin friction as the required reaction force to cause the pile tip settlement, provides a solution to perform more pile loading tests and consequently a more economical pile design is possible. The separate measurement of skin friction and tip resistance during the course of performing SPLT provides a better understanding of the pile behavior than the result of the conventional pile loading test where only the total resistance is measured. On the other hand, there are some points to be clarified in order to apply the test results of SPLT to practical problem. They are the direction of the applied load to mobilize the skin friction and the use of reduced sized sliding core. In this research, both the SPLT and the conventional pile loading test on 406mm diameter steel pipe pile have been performed. From the result, it would be safe to use the measured SPLT skin friction value directly in the design, since the value is somewhat lower than the value measured in the conventional test. It is further assumed that the tip resistance value of the reduced sized sliding core should properly be analysed by taking the incluonce of scale effect into consideration.

• Journal of the Korean Geophysical Society
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• v.1 no.1
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• pp.59-68
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• 1998

Ground penetrating radar (GPR) experiments were performed in a sand tank to study the ability of detection of buried pipes and to characterize the signal of the reflection wave. The ratios of diameter of buried pipes to the depth were set 4 up to 24 % and materials were metal, synthetic resin, and wood. In case of groundwater table below buried materials, strong reflection signals were observed irrespective of diameter and depth except for wood. While it is very difficult to detect the reflection signals in case that the groundwater table is set to higher than buried materials. The reflection signals from the bottom of the sand tank, however, were clearly observed even in case of higher groundwater table. This implies that the weak reflection signals from the buried materials are not all due to the wave attenuation. The vertical reflection profiling method is recommended in case that the object of the survey is to find horizontal position of buried material because this method has the advantage in cost and time of survey. However, the full or partial CMP gather method is recommended in case that the objects of the survey are to get the detailed subsurface information, i.e. the depth to buried material, interval velocity of geological layer, and mapping the groundwater table.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3B
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• pp.205-209
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• 2011

The low carrying capacity caused by the deposition in a sewer line is one of the main reason of the urban flood. Therefore, an efficient maintenance and management of the storm water drainage system is very important to prevent urban flood. In this research, the sediment transport characteristics through a pressure pipeline were examined with laboratory experiments. Bed-forms in a pipeline, sediment rates, roughness due to sediments were examined. Experimental system consists of flow circulation system with a pump and a sediment feeder at the upstream of the pipeline. Sediments were supplied into a 60 mm-diameter and 8 m-long pipe. Maximum flow rate is $30m^3/hr$, and the sediment feeding rate range is 5 g/s~19 g/s. Governing parameters and estimation equation for sediment transport rate were developed. The mean velocity (U), coefficient of viscosity (${\mu}$), unit width bed load ($q_b$), mean diameter of particle ($d_{50}$), unit weight of sediment in water (${\gamma}^{\prime}_s$) were adopted as the most influencing factors of sediment transport patterns. The prediction equation for sediment transport rate were developed with two dimensionless terms. These two dimensionless terms showed a linear relationship with high correlation coefficient.

• Journal of Bio-Environment Control
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• v.22 no.2
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• pp.123-130
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• 2013

$CO_2$ enrichment systems have been recently used to shorten the growth period of plants and the improvement of harvest and its quality. To accomplish these goals, manifold should be designed to supply the same amount of $CO_2$. In this study, CFD approach has been used to understand the effects of geometric parameters, such as tube and hole diameters. An optimized geometry has been derived through pipe and tube part, respectively. As a result, the deviation of flow rate less than 0.1 g/s was expected at all holes of the $CO_2$ enrichment system.