• Journal of Korean Society of Environmental Engineers
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• v.33 no.10
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• pp.723-730
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• 2011

In this experiment, persulfate, a strong oxidant for ISCO (In-Situ Chemical Oxidation) was used to degraded RDX in artificial ground water at ambient temperature. Results of RDX degradation by persulfate in a batch reactor showed that the oxidation reaction was pseudo first order with estimated Ea (activation energy) of $1.14{\times}10^2kJ/mol$ and the rate was increased with the increase of reaction temperature. The oxidation of RDX by persulfate increased slightly with the increase of initial solution pH from 4 to 8. The RDX oxidation rate increased 13 times at pH 10 compared with that at pH 4, however, alkaline hydrolysis was found to be the main reaction of RDX degradation rather than oxidation. The study also showed that the oxidation rate of RDX by persulfate was linearly dependent upon the molar ratios of persulfate to RDX from 5 : 1 up to 100 : 1, with a proportion constant of $4{\times}10^{-4}$ ($min^{-1}$/molar ratio) at $70^{\circ}C$. While NOM (Natural Organic Matter) exerted negative effects on the oxidation rate of RDX by persulfate, with a proportion constant of $1.21{\times}10^{-4}$ ($min^{-1}{\cdot}L/mg-NOM$) at $70^{\circ}C$ and persulfate/NOM molar ratio of 10/1. The decrease in RDX oxidation rate was linearly dependent upon the added NOM concentration. However, the estimated activation energy in the presence of 20 mg-NOM/L was within 3.3% error compared to that without NOM, which implies the addition of NOM does not alter intrinsic oxidation reaction.

• International Journal of Highway Engineering
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• v.13 no.4
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• pp.231-238
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• 2011

Variable message signs(VMS) in use are being displaying with the LED device as the luminous source, and it is a recent trend to be changed from the Lamp type to the Surface-Mount Devices(SMD) type. The LED device leads to get VMS display brightly and clearly, leading to have visibility and legibility better than the existing VMS. However, the lights which display off the road, the unnecessary energy, might have negative effect on ecosystem. This study developed the way of getting the lights be displayed only to drivers without the unnecessary energy and estimated the energy efficiency of the development by the optical testing. As a result, this study showed that the energy consumption of the developed display device appeared to decrease by about 36.1% compared to the existing device. Also the upward and downward angle of the lights changed from an angle of $24^{\circ}C$ to $0^{\circ}C$and from an angle of $-24^{\circ}C$ to $-11^{\circ}C$, respectively. Therefore, it anticipates that the developed device would benefit highway safety due to an improvement in visibility and legibility compared to the existing VMS and the energy consumption would be less lower than the existing VMS.

• Journal of the Microelectronics and Packaging Society
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• v.22 no.1
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• pp.15-19
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• 2015

We demonstrated an inspection system for detecting discoloration of PCB Cu ball pad with an OSP surface finish. Though the OSP surface finish has many advantages such as eco-friendly and low cost, however, it often shows a discoloration phenomenon due to a heating process. In this study, the discoloration was analyzed with device-independent CIELAB color space. First of all, the PCB samples were inspected with standard lamps and CCD camera. The measured data was processed with Labview program for detecting discoloration of Cu ball pad. From the original PCB sample image, the localized Cu ball pad image was selected to reduce the image size by the binarization and edge detection processes and it was also converted to device-independent CIELAB color space using $3{\times}3$ conversion matrix. Both acquisition time and false acceptance rate were significantly reduced with this proposed inspection system. In addition, $L^*$ and $b^*$ values of CIELAB color space were suitable for inspection of discoloration of Cu ball pad.

• Journal of the Korea Convergence Society
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• v.10 no.12
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• pp.129-134
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• 2019

PVC was chosen as a plastic product that can cope with lead, a radiation shielding material that is widely used in medical institutions. In addition to radiation shielding clothing, we want to evaluate whether it can be used as a medical device component and industrial shielding material in low dose areas. Commercial PVC has a density of 3.68 g/㎠ and can be positively expected sufficient shielding effect in certain radiation areas such as material flexibility and economy efficiency, and can be transformed into various forms and used as a lightweight shielding wall. The shielding performance was tested by adjusting the thickness of 5 sheets of 3mm PVC in the range of medical radiation used for clinical examination in medical institutions. Shielding performance against effective energy was evaluated based on tube radiation voltage of medical radiation. The thicker the PVC, the lower the tube voltage and the lower the effective energy, the greater the shielding effect. The shielding effect was 70% at 12mm thickness and 80kVp tube voltage. Therefore, the shielding effect of PVC material has a high dependence of thickness. In the future, continuous research is needed to make thin and light eco-friendly products while improving shielding performance.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.5
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• pp.509-515
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• 2012

In this study, ${\gamma}-Al_2O_3$ nanoparticles were synthesized by using coflow hydrogen diffusion flames. The synthesis conditions were varied with using several oxygen concentrations in the oxidizing air. The particle characteristics of the flame-synthesized $Al_2O_3$ nanoparticles were determined by examining the crystalline structure, shape, and specific surface area of the nanoparticles. The measured maximum centerline temperature of the flames ranged from 1507.8 K to 1998.7 K. The morphology and crystal structure of the $Al_2O_3$ nanoparticles were determined from SEM images and XRD analyses, respectively. The particle sizes were calculated from measured BET specific surface areas and ranged from 25 nm to 52 nm. From XRD analyses, it was inferred that a large number of the synthesized nanoparticles were ${\gamma}-Al_2O_3$ nanoparticles including ${\theta}-Al_2O_3$ nanoparticles.

• Journal of the Korean Society of Marine Environment & Safety
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• v.24 no.6
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• pp.818-824
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• 2018

CFRP is often used as lightweight hull material for luxury yachts or special-service ships. An electric propulsion system is also eco-friendly, and has been trialled to equip a small vessel as its main propulsion. In this study, replacing the hull materials and propulsion system with CFRP and electric motors, we made an estimate of the effect of weight reduction and compared it to the original design, for this purpose a case study was conducted on a 45-ft yacht. When redesigning structures with CFRP, we applied the reinforcement content of the carbon fiber in the same way as the original (GC = 0.4), and when changing to the electric propulsion system, we designed motors and battery packs to achieve the same performance as the original. The result showed that CFRP and the electric propulsion system could make the structural and machinery weights 45 % and 58 % lighter, respectively. However, in terms of efficiency, it was confirmed that the electric propulsion system is practically inefficient because it requires a huge amount of battery packs for the same navigation range with diesel engines.

• Korean Journal of Environmental Agriculture
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• v.31 no.3
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• pp.235-247
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• 2012

BACKGROUND: Gohyeon Stream is the municipal eco-stream of 7.1km in total length which flows through the downtown area of Gohyeon in Geoje city, rising from the watershed of Mundong Water Fall. Gohyeon district in Geoje city has been a rapid growing area centering in Geoje city and then experienced an rapid increase in population. Large amounts of sewage pollutants have been spewed into Gohyeon Stream from its tributaries, due to the lack of sewer system. Gohyeon Stream is laced with unhealthy levels of fecal coliform (FC). Restoration of water quality in Gohyeon Stream is no less inevitable in behalf of its ecosystem and the citizen. In this study, the water quality of Gohyeon Stream and its tributaries was examined temporally and spatially, and their relationships were comparatively analyzed to give useful basic data applying to a restoration project of the water quality of Gohyeon Stream. METHODS AND RESULTS: The samples ware taken at 20 points in Gohyeon Stream and 19 points in its tributaries during the rainy and dry seasons, respectively, and examined on the parameters of pH, temperature, salinity, dissolved oxygen (DO), suspended solid (SS), biochemical oxygen demand (BOD), chemical oxygen demand (COD), dissolved inorganic nitrogen (DIN; $NH_3$-N, $NO_3$-N, $NO_2$-N), disolved inorganic phosphorus (DIP; $PO_4$-P) and FC. The data were analyzed using a comparative analysis and Pearson's correlation analysis among the parameters. During the rainy season, the concentration of SS was high in the upper region of Gohyeon Stream, and the concentrations of COD, DIN and DIP were low in the upper region and high in the middle and lower regions. During the dry season, the concentration of SS was low and the concentrations of COD, DIN, DIP and FC were high in all regions. The Pearson's correlation analyses showed that the relationships between DO and FC, COD and DIP, and DIN and FC during the rainy season as well as between DO and DIN, SS and FC, COD and DIP, and DIN and DIP during the dry season were significant. CONCLUSION: During the rainy season, the upper region of Gohyeon Stream flowed the high level of SS, the middle region the high level of nutrients due to an agricultural run-off, and the lower region the high level of nutrients due to a sewage inflow. During the dry season, the water quality of Gohyeon Stream was directly and sensitively influenced on the inflow of sewage from the tributaries.

• Ecology and Resilient Infrastructure
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• v.7 no.1
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• pp.72-81
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• 2020

Blooms of the small centric diatom Stephanodiscus is quite occasional in winter season in temperate freshwater ecosystems. Often, it leads to degradation of water quality and affects quality of supplied drinking water. In previous studies, naphthoquinone (NQ) compounds have been shown to be effective and selective for controlling winter bloom species Stephanodiscus hantzschii. We conducted a 5 ton scale mesocosm experiment to investigate the effects of NQ on native Stephanodiscus sp. collected from Nakdonggang River in water. After treatment with NQ 4-6 compound (0.2 μM), the cell density of Stephanodiscus sp. was rapidly reduced from 5 × 10³ cells mL^-1 to 0.2 × 10³ cells mL^-1 for 10 days. Additionally, NQ 4-6 compound did not affect physicochemical factors (water temperature, dissolved oxygen, pH, conductivity, nutrients) and biological factors (bacteria, heterotrophic nanoflagellates, zooplankton). Therefore, these findings suggest that the NQ 4-6 compound has potential as an alternative algicidal substances to effectively mitigate natural Stephanodiscus sp. blooms, and the application of NQ 4-6 compound will restore the healthy aquatic ecosystems.

• The Journal of the Korea institute of electronic communication sciences
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• v.10 no.11
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• pp.1271-1276
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• 2015

The recent trend is that diesel power generation on islands where its prime cost for power generation is high is replaced by new and renewable energy. Therefore, south Jeolla province is progressing the construction project of self-sufficient islands for the areas where power is supplied by depending on diesel generators, which is the project that power is supplied through eco-friendly energy source using sunlight, wind power and energy storage device etc. However, it is difficult to construct new and renewable energy source with the capacity to respond to the load perfectly due to its environmental and geographical conditions regarding capacity design of new and renewable energy. Besides, Microgrid design considering appropriate capacity design of the system components and efficient operation is required through the analysis of climate conditions and load patterns from the design stage for optimal composition of a hybrid system with economic feasibility. Therefore, this study is aimed to conduct a research on optimal combination, capacity calculation and economic feasibility by comprising a hybrid power generation system which will replace 40% of power generation by diesel as new and renewable energy source for Geomun Island where has more than 300 households and requires expansion of the facility among islands located in southwest coast.

• Journal of Korea Water Resources Association
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• v.53 no.10
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• pp.833-843
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• 2020

Ecohydraulics is a newly born discipline in the early 1990s by the interdisciplinary approach combined with aquatic ecology in one discipline and geomorphology, hydrology, and fluid hydrodynamics in another. Major areas of ecohydraulics can be delineated as habitat hydraulics (including environmental flow), vegetation hydraulics, eco-corridor hydraulics, eutrophication hydraulics, and ecological restoration hydraulics. Reviews of relevant international journals and literature reveal that ecohydraulics has remained in the limited areas of fish response, hydraulic modeling, and physical habitat response. It has not reached a truly interdisciplinary stage. Literature reviews in Korea reveal that only 3% of the total number of the papers listed in the Journal of KWRA during the last 24 years is related to ecohydraulics. It is about 20% of the total listed in the Journal of Ecology and Resilient Infrastructure. Most of those related to ecohydraulics in Korea concern vegetation hydraulics, habitat hydraulics, and ecological restoration hydraulics. In contrast, dynamic flow modeling areas, including turbulence, fauna motion simulation, and eutrophication hydraulics, are not found. Areas of further research in ecohydraulics in Korea may be specified as follows: 1) environmental flows adapted to the traits of the rivers in Korea, 2) development of the dynamic floodplain vegetation models (DFVM) to assess the changes from the white river to green river, 3) development of the eutrophication hydraulic model to predict the freshwater algal blooms, and 4) development of the models to evaluate the physical, chemical, and biological impacts of the stream restoration, decommissioning and removal of old weirs or small dams.