• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.11
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• pp.7990-8000
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• 2015

Plant factories are plant cultivation systems which produce farm products uniformly under the controlled environmental condition regardless of seasons and places. Thermal flow in the plant factory is an important parameter in cultivating plants. In this research, we study thermal flow characteristics for a hybrid plant factory with multi-layer cultivation shelves using computer simulation techniques. In order to obtain numerical solutions for thermal flow characteristics, a finite volume method was applied. We consider a low-Reynolds-number ${\kappa}-{\epsilon}$ turbulence model, incompressible viscous flows, and pressure boundary conditions for numerical simulation. Commercial software Solid Works Flow Simulation is then used to investigate characteristics of thermal flows in the plant factory applying several different inflow air velocities and arrangements of cultivation shelves. From numerical analysis results, we found that temperatures in cultivation shelves were uniformly distributed for Case 3 when the inflow air velocity was 1.6 m/s by using a blower in the plant factory. However in Case 1 lower temperature distributions were observed in test beds, TB2 and TB3, which indicated that additional temperature control efforts would be required. Average shelf temperature increased by $3^{\circ}C$ using artificial light source (DYLED47) with 50% blue and 50% red LED ratios. Korea Academia-Industrial cooperation Society.

• Journal of Korea Water Resources Association
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• v.50 no.8
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• pp.521-535
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• 2017

Acoustic Doppler Current Profilers (ADCPs) have been widely utilized for assessing streamflow discharge, yet few comprehensive studies were conducted to evaluate discharge uncertainty in consideration of individual uncertainty components. It could be mostly because it was not easy to determine which uncertainty framework can be appropriate to rigorously analyze streamflow discharge driven by ADCPs. In this regard, considerable efforts have been made by scientific and engineering societies to develop a standardized theoretical framework for uncertainty analysis in hydrometry. One of the well-established UA methodology based on sound statistical and engineering concepts is Guide to the Expression of Uncertainty Measurement (GUM) adopted widely by various scientific and research communities. This research fundamentally adapted the GUM framework to assess individual uncertainty components of ADCP discharge measurements, and subsequently provided results of a customized experiment in a controllable real-scale artificial river channel. We focused particularly upon sensitivities of uncertainty components in the GUM framework driven by ADCPs direct measurements such as depths, edge distance, submerged depth, velocity gap, sampling time, repeatability, bed roughness and so on. Section-by-Section method for ADCP discharge measurement was applied for uncertainty analysis for this study. All of measurements were carefully compared with data using other instrumentations such as ADV to evaluate individual uncertainty components.

• 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 Soil and Groundwater Environment
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• v.10 no.6
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• pp.20-31
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• 2005

Three dimensional Monte-Carlo simulations of non-ergodic transport of a lion-reactive solute plume by steady-state groundwater flow under a uniform mean velocity in isotropic heterogeneous aquifers were conducted. The log-normally distributed hydraulic conductivity, K(x), is modeled as a random field. Significant efforts are made to reduce tile simulation uncertainties. Ensemble averages of the second spatial moments of the plume and plume centroid variances were simulated with 1600 Monte Carlo runs for three variances of log K, ${\sigma}_Y^2=0.09,\;0.23$, and 0.46, and three dimensionless lengths of line plume sources normal to the mean velocity. The simulated second spatial moment and the plume centroid variance in longitudinal direction fit well to the first order theoretical results while the simulated transverse moments are generally larger than the first order results. The first order theoretical results significantly underestimated the simulated dimensionless transverse moments for the aquifers of large ${\sigma}_Y^2$ and large dimensionless time. The ergodic condition for the second spatial moments is far from reaching in all cases simulated, and transport In transverse directions may reach ergodic condition much slower than that in longitudinal direction. The evolution of the contaminant transported in a heterogeneous aquifer is not affected by the shape of the initial plume but affected mainly by the degree of the heterogeneity and the size of the initial plume.

• Journal of Korean Society of Environmental Engineers
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• v.35 no.11
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• pp.835-860
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• 2013

Recently, the consumption of nanomaterials has been significantly increased in both industrial and commercial sectors, as a result of steady advancement in the nano-technologies. This ubiquitous use of nanomaterials has brought up the concern that their exposure to environments may cause detrimental effects on human health as well as natural ecosystems, and it is required to characterize their behavior in various environmental media and to evaluate their ecotoxicity. For the sake of accomplishing those assessments, the development of methods to effectively separate them from diverse media and to quantify their properties should be requisitely accompanied. Among a number of separation techniques developed so far, this study focuses on Field-Flow Fractionation (FFF) because of its strengths, such as relatively less disturbance of samples and simple pretreatment, and we review overseas and domestic literatures on the separation of nanomaterials using the FFF technique. In particular, researches with Flow Field-Flow Fractionation (FlFFF) are highlighted due to its most frequent application among FFF techniques. The basic principle of the FlFFF is briefly introduced and the studies conducted so far are classified and scrutinized based on the sort of target nanomaterials for the purpose of furnishing practical data and information for the researchers struggling in this field. The literature review suggests that the operational conditions, such as pretreatment, selection of membrane and carrier solution, and rate (velocity) of each flow, should be optimized in order to effectively separate them from various matrices using the FFF technique. Moreover, it seems to be a prerequisite to couple or hyphenate with several detectors and analyzers for quantification of their properties after their separation using the FFF. However, its application has been restricted regarding the types of target nanomaterials and environmental media. Furthermore, domestic literature data on both separation and characterization of nanomaterials are extremely limited. Taking into account the overwhelmingly increasing consumption of nanomaterials, the efforts for the area seem to be greatly urgent.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.3
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• pp.279-293
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• 1995

The most obvious and easily recognizable sources of potential water pollution are point sources such as domestic and industrial wastes. But recently, the potential effects of nonpoint sources on water quality have been increased apparently. In order to evaluate the characteristics and the effects of nonpoint sources on water quality, this study was performed in Suyeong Bay from May, 1992 to July, 1992. The depth-averaged 2-dimensional numerical model, which consists of the hydrodynamic model and the diffusion model was applied to simulate the water quality in Suyeong Bay. When flowrate was $65.736m^3/s,$ the concentration of pollutants (COD, TSS and VSS) at Oncheon stream (Sebeong bridge) during second flush were very high as much as 121.4mg/l of COD, 1148.0mg/l of TSS and 262.0mg/1 of VSS. When flowrate was 4.686m^3/s, the concentration of pollutants $(TIN,\;NH_4\;^+-\;N,\;NO_2\;^--N\;and\;PO_4\;^{3-}-P)$ during the first flush were very high as much as 20.306mg/1 of TIN, 14.154mg/1 of $NH_4\;^+-N$, 9.571mg/l of $NO_2\;^--N$ and l.785mg/l of $PO_2\;^{3-}-P$ As results of the hydrodynamic model simulation, the computed maximum velocity of tidal currents in Suyeong Bay was 0.3m/s and their direction was clockwise flow for ebb tide and counter clockwise flow for Hood tide. Four different methods were applied for the diffusion simulation in Suyeong Bay. There were the effects for the water quality due to point loads, annual nonpoint loads and nonpoint loads during the wet weather and the investigation period, respectively. The efforts of annual nonpoint loads and nonpoint loads during the wet weather seem to be slightly deteriorated in comparison with the effects of point loads. However, the bay was significantly polluted by the nonpoint loads during the investigation period. In this case, COD and SS concentrations ranged 2.0-30.0mg/l, 7.0- 200.0mg/l in ebb tide, respectively. From these results, it can be emphasized that the large amount of pollutants caused by nonpoint sources during the wet weather were discharged into the bay, and affected significantly to both the water quality and the marine ecosystem. Therefore, it is necessary to consider the loadings of nonpoint pollutants to plan wastewater treatment plant.