• Journal of the Korean Society of Visualization
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• v.20 no.3
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• pp.86-93
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• 2022

An electrostatic precipitator (ESP) is an industrial post processing facility for high efficiency dust mitigation. Uniformity of the flow passing through the inlet duct leading into the main chamber is important for efficient reduction of dust. To examine flow uniformity, this study conducted a numerical analysis of the flow within a scale-down ESP inlet duct. Magnetic resonance velocimetry (MRV) results from a prior study were utilized to validate the Reynolds-averaged Navier-Stokes (RANS) numerical simulations. Both the experimental and computational results displayed a similar recirculation zone shape and normalized velocity profile near the duct outlet for the baseline geometry. To optimize the uniformity of the flow, the number of guide vanes was modified, and the guide vanes were partially extended straight upward. Design evaluation is done based on the outlet velocity distribution and mass flowrate balance between the two outlets. Simulation results indicate that the vane extension is critical for flow optimization in curved ESP ducts.

• Particle and aerosol research
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• v.18 no.3
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• pp.61-68
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• 2022

In this study, a fluidized bed particle generator was developed to generate an aerosol without supply of compressed air and to increase portability. It was assumed that the mixing ratio of the test particles and beads, the input amount, and the air flow rate supplied to the generator would have effect on the aerosol generation characteristics. The product of these three parameters was set as a characteristic parameter and particle generation characteristics according to the change of the characteristic parameter were observed. As a result, it was confirmed that the input amount of test particles and beads was not suitable as a characteristic parameter and a characteristic parameter expressed as a product of the mass mixing ratio and the air flowrate was newly defined. When the new characteristic parameter is applied, it can be confirmed that the total amount of particles generated from the particle generator is a function of the characteristic parameter. As a result of measuring the amount of particle generation by adjusting the characteristic parameter, it was confirmed that the performance required for the test particle generator for the field inspection equipment of PM-2.5 sensors could be satisfied.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.37-37
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• 2023

There is currently a high-accuracy modern forecasting method that uses machine learning algorithms or artificial neural network models to forecast river water levels or flowrate. As a result, this study aims to develop a mathematical model based on artificial neural networks to effectively forecast river water levels upstream of Tranh Culvert in North Vietnam's Bac Hung Hai irrigation system. The mathematical model was thoroughly studied and evaluated by using hydrological data from six gauge stations over a period of twenty-two years between 2000 and 2022. Furthermore, the results of the developed model were also compared to those of the long-short-term memory neural networks model. This study performs four predictions, with a forecast time ranging from 6 to 24 hours and a time step of 6 hours. To validate and test the model's performance, the Nash-Sutcliffe efficiency coefficient (NSE), mean absolute error, and root mean squared error were calculated. During the testing phase, the NSE of the model varies from 0.981 to 0.879, corresponding to forecast cases from one to four time steps ahead. The forecast results from the model are very reasonable, indicating that the model performed excellently. Therefore, the proposed model can be used to forecast water levels in North Vietnam's irrigation system or rivers impacted by tides.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.5
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• pp.85-91
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• 1997

Air grinding time in grinding process has a great effect on its efficiency due to low feedrate. This paper presents a reduction methos of air grinding time in cylindrical plunge grinding operation. Tje reduction of air grinding time is accomplished by finding the distance between contact point and rising point of ultra- sonic signal of the grinding wheel to workpiece. It uses a variation of sound signal generated by the flow of coolant when the grinding wheel approaches to workpiece. The ultrasonic sensor with 23 kHz center fre- quency and 8 kHz bandwidth is used to find the nearest approaching point(NAP). Monitoring and control system of the grinding conditions is implemented with CNC controller to control feedrate override and ultrasonic sensor to find NAP. The experimental result shows that the ultrasonic signal is a good measure- ment to find NAP. But it needs the considerations for the effect of the relationship between flowrate of coolant and diameter of workpiece.

• Analytical Science and Technology
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• v.20 no.1
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• pp.55-60
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• 2007

A sensitive technique for the determination of trace Cu(II) in various samples after the column preconcentration by adsorbing its N-benzoylphenylhydroxylamine (BPHA) onto benzophenone was developed. Several experimental conditions such as the pH of the sample solution, the amount of chelating agent, the amount of benzophenone, and the flowrate of sample solution and so forth were optimized. The interfering effects of diverse concomitant ions were investigated. Fe(III) and $CN^-$ interfered with more seriously than any other ions. However, the interference by these ions could be overcome sufficiently by adjusting the added volume of 0.01M BPHA to 10 mL. The dynamic range, the correlation coefficient ($r^2$) and the detection limit obtained by this proposed technique were 5.0~120 ng/mL, 0.9974, and 2.1 ng/mL, respectively. For validating this proposed technique, the aqueous samples (stream water, reservoir water, and wastewater), the plastic sample and the diluted brass sample were used. Recovery yields of 93~102% were obtained. These measured data were not different from ICP-MS data at 95% confidence level. This method was also validated by the rice flour CRM (normal, fortified) samples. Based on the results from the experiment, it was found that this proposed technique could be applied to the determination of Cu(II) in various real samples.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.389-389
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• 2022

상수도 관망에서의 유량 측정은 유수율을 결정하는 데 있어서 중요한 평가 수단이다. 따라서, 유량 측정을 위해 유량계를 활용하는데, 높은 빈도의 자료를 획득할 수 있는 수압계는 시중에서 저가로 활용 가능하지만, 상수도관망 예산의 상당부분을 차지하고 있는 유량계는 수압계보다 고가에도 낮은 빈도의 자료만을 획득하는 비용 대비 낮은 효율을 가진다. 만약 수압계의 측정자료를 유량자료로 고속전환하는 기술을 개발하면 기존의 유량계보다 적은 비용으로 고빈도의 유량자료를 획득할 수 있다. 상수도 관망에서 수압자료를 유량 자료로 전환하는 기술은 기존 관망에서 유도된 지배방정식에서 임의 관망에서 일련의 유도과정을 거쳐 상하류 단사이 수압과 유량의 관계를 형성하고, 이러한 관계를 활용하여 간단한 저수조-관망-밸브 체제에서 관망 내의 특정지점에서의 시간상 수압자료와 시간상 유량자료의 비를 정의한 다음, 임의의 지점에서 측정된 수압자료를 정의한 비로 나타나는 임피던스 역수를 역푸리에 전환하면 시간상의 유량자료를 획득할 수 있는 원리이다. 이러한 수압-유량 전환기술의 원리를 가지고 개발된 기술의 정확도를 확인하는 과정을 수행하였으며, 이는 전통적 천이류 해석 방법인 특성선 모델로 비교하는 수치해석적인 방법 그리고 실제 설치된 관망을 사용해서 수압을 측정하고, 지정된 지점에서 유량을 정밀측정하여 비교하는 실험적인 방법을 통해 정확도를 비교해봄으로써 개발된 기술을 검증해보고자 한다.

• Journal of Korea Water Resources Association
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• v.42 no.12
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• pp.1091-1102
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• 2009

This study developed an integrated approach to climate change and urbanization impact assessment by linking models of SDSM (statistical downscaling model), HSPF (hydrological simulation program?Fortran) and ICM (impervious cover model). A case study of the Anyangcheon watershed illustrated how the proposed framework can be used to analyze the impacts of climate change and urbanization in terms of flood control, water security and water quality. The evaluation criteria were the variations of flow and pollutant concentration duration curves. In this study, nine scenarios including three climate (present condition, A1B and A2) and three urbanization scenarios were analyzed using HSPF model. As a result, climate change is a large influence on the flowrate and the urbanization affects the pollutant concentration. Therefore, the impacts of both climate change and urbanization must be included into the watershed management and water resources planning for sustainable development.

• Korean Journal of Soil Science and Fertilizer
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• v.46 no.6
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• pp.458-462
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• 2013

A drainage ditch is normally a component of drainage networks in farming systems to remove surplus water, but at the same time, it may act as a major conduit of agricultural nonpoint source pollutions such as sediment, nitrogen, phosphorus, and so on. The hybrid turbidity reduction system using biodegradable check dam and synthetic polymer was developed in this study to manage pollutant discharge from agricultural farmlands during rainfall events and/or irrigation periods. The performance of this hybrid system was assessed using a laboratory open channel sized in 10m-length and 0.2m-width. Various check dams using agricultural byproducts (e.g., rice straw, rice husks, coconut fiber and a mixture of rice husks and coconut fiber) were tested and additional physical factors (e.g., channel slope, flowrate, PAM dosage, turbidity level, etc.) affecting on turbidity reduction were applied to assess their performance. A series of lab experiments clearly showed that the hybrid turbidity reduction system could play a significant role as a supplementary of Best Management Practice (BMP). Moreover, the findings of this study could facilitate to develop an advanced BMP for minimizing nonpoint source pollution from agricultural farmlands and ultimately to achieve the sustainable agriculture.

• Clean Technology
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• v.22 no.3
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• pp.168-174
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• 2016

The working environment is deteriorated due to a rise in temperature of a coal mine caused by increase of its depth and carriage tunnels. To improve the environment, the temperature distribution resulted by using the fan type ventilation system aiming for the temperature drop is calculated by using a fluid dynamic analysis program. The analysis shows that A coal mine needs 6,152 m³ min^-1 for in-flow ventilation rate but the total input air flowrate is 4,710 m³ min^-1, 1,442 m³ min^-1 of in-flow ventilation rate shortage and the temperature between the carriage tunnel openings and the workings with exhausting ventilation system type is 2~3 ℃ less than that with blowing ventilation system type. The exhausting ventilation system type would be more effective than blowing ventilation system when the distance between the carriage tunnel openings and the workings is relatively far.

• Plant Journal
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• v.16 no.1
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• pp.34-37
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• 2020

The need to improve the performance of the dust collector by increasing the fine dust pollution in Korea is eminent. In this study, electrostatic spray wet electrostatic precipitator is used to remove Particulate Matter (PM). In order to enter the Cone-jet mode, which is the most stable spray mode among the various modes of electrostatic spraying, an appropriate voltage-flow condition must be satisfied, and a voltage-flow interval enabling this can be expressed as Stability Island. The voltage at which the conduit mode starts in the Stability Island section is referred to as the electrostatic spray minimum voltage (Onset Voltage). However, the conventional electrostatic spray is uses a very low flowrate, at most few millilitres per minute. The use of much higher flowrates has introduced different patterns of electrospray modes. In this study, the different spray modes will be studied in detail.