Saeromi Lee

Design of the Compact UWB Antenna With PI-shaped Matching Stub

In this paper, we have proposed a compact UWB antenna with PI-shaped (π-shaped) matching stub for UWB applications. The antenna has a modified trapezoidal radiating patch, a PI-shaped matching stub, CPW feeding, and two steps for impedance matching. A prototype antenna printed on the dielectric substrate of FR4 has dimensions of 20 mm by 20 mm. The proposed antenna exhibits a voltage standing wave ratio (VSWR) of less than 2.0, and the figure-of-eight radiation patterns with gain from 2 to 3.5 dBi in a frequency range from 3.1 to 10.6 GHz. To evaluate the dispersion performance of the designed UWB antenna, the path loss (|S21|) and the group delay are simulated and measured. Details of the proposed antenna design and the simulated and measured results are presented and discussed.

Field application of waterworks automated meter reading systems and analysis of household water consumption

AbstractAfter the construction of waterworks automated meter reading (AMR) systems with a 15-mm diameter smart water meter developed in this study, both the feasibility of field application of waterworks AMR and the patterns of household water consumption were evaluated. Average reception rate was 94.1% due to the communication blackout, and one-to-one communication with RF UHF and Internet (i.e. TCP/IP) was found to be more stable in AMR systems than multiple-to-one communication with RF UHF, DCU, and Wibro. Household water consumption clearly showed seasonal periodicity due to weather factors. Based on the analysis of liters per capita day (LPCD) for 80 households, the LPCD values were found to decrease gradually as the number of residents increased due to the saving effects through common consumption (i.e. washing, cooking, cleaning, irrigation, etc.). Relative to LPCD values of 100 control households without AMR systems, the LPCD values of 80 pilot households with AMR systems were reduced by 5.3%. Con...

Analysis of Water Quality Improvement of Ceratophyllum demersum under Laboratory Condition - by Nutrients Removal Efficiency

To evaluate the ability of the submerged plant, Ceratophyllum demersum’s (C. demersum) to remove nutrients and to inhibit growth of cyanobacteria, a total of 6 mesocosms were conducted in a batch reactor for 9 days. From the 84 hr of the experiment, C. demersum was stabilized and showed daily cycle trends according to changes in pH and DO levels. The concentration of nutrients, NH3, NO3 and PO4 continuously decreased until 9 days of the experiment, with the rapid decrease in nutrient concentration for the first 24 hours. High correlation coefficient (r≥ 0.96, p < 0.001) between the amount of C. demersum’s biomass per unit area and the nutrients removal level were derived, and greater C. demersum’s biomass per unit area showed higher removal efficiency of nutrients. However, there were differences in the C. demersum’s activity level between batch reactors with higher and similar density of the C. demersum, but nonetheless water purification effect appears to have a significant influence due to attached algae and microorganisms. The growth rate of harmful cyanobacteria, Microcystis aeruginosa (M. aeruginosa) with C. demersum’s density of 2,500 g fw/m (100% of cover degree) was 0.31 /day, compared to the growth rate of 0.47 /day for the control group (0% of cover degree). In terms of number of cells, the control group had 1.7 times higher number of cells than the experimental group, proving that C. demersum has the ability to inhibit the growth of harmful cyanobacteria.

An Experimental Approach to Secure Freshwater Fish Shelter according to the Water Level Fluctuations in a Shallow Pond

Physical disturbance, which induces a lack of flow rate, frequently occurs in freshwater ecosystem. Due to this, it is required to provide a new fish shelter to resolve. We installed a pilot scale test-bed to scrutinize the relationship between water level and the influence of fish shelter. The proposed ADP (artificial deep pool) is a fish shelter which composed of concrete materials. From the monitoring results in test-bed, it was observed that the population of fish was the highest at the 0.5 m in depth from the water level of experimental pond. But it was more appropriate for shallow water level (<0.3 m) to conserve the total number of fish by increasing the number per unit area despite of lower inner temperature and DO than outer environment. Therefore, inner of ADP was more efficient lentic system for fish to live due to higher WCS, OS, SS, and TS. In addition, there was a relative abundance of WCS fish species such as Acheilognathus koreensis (A. koreensis), Carassius carassius (C. carassius). Considered these results, it is suggested that ADP is appropriate to use for fish shelter and habitat for the fishes in lentic ecosystem.

Evaluation on Removal Efficiency of Methylene Blue Using Nano-ZnO/Laponite/PVA Photocatalyzed Adsorption Ball

In order to overcome drawbacks (i.e., filtration and recovery) of conventional powder type photocatalysts, nano-ZnO/Laponite/PVA (ZLP) photocatalyzed adsorption balls were developed by using in situ mixing of nanoscale ZnO as a photocatalyst, and Laponite as both adsorbent and supporting media in deionized water, followed by the poly vinyl alcohol polymerization with boric acid. The optimum mixing ratio of nano-ZnO:Laponite:PVA:deionized water was found to be 3:1:1:16 (by weight), and the mesh and film produced by PVA polymerization with boric acid might inhibit both swelling of Laponite and detachment of nanoscale ZnO from ZLP balls. Drying ZLP balls with microwave (600 watt) was found to produce ZLP balls with stable structure in water, and various sizes (55~500 ) of pore were found to be distributed based on SEM and TEM results. In the initial period of reaction (i. e., 40 min), adsorption through ionic interaction between methylene blue and Laponite was the main removal mechanism. After the saturation of methylene blue to available adsorption sites for Laponite, the photocatalytic degradation of methylene blue occurred. The effective removal of methylene blue was attributed to adsorption and photocatalytic degradation. Based on the results from this study, synthesized ZLP photocatalyzed adsorption balls were expected to remove recalcitrant organic compounds effectively through both adsorption and photocatalytic degradation, and the risks of environmental receptors caused by detachment of nanoscale photocatalysts can be reduced.

Application of Titanium Dioxide (TiO2)-Embedded Buoyant Photocatalyst Balls Using Expanded Polystyrene

A new immobilization technique of nanoscale TiO₂ powders to expanded polystryrene (EPS) balls with temperature-controlled melting method was validated for mass production, and the photocatalytic activity of TiO₂ powder-embedded EPS (TiEPS) balls using methylene blue (MB) solution with different concentrations under ultraviolet irradiation and under the natural solar light irradiation. Whereas MB molecules were weakly adsorbed onto the surface of both TiO₂ powders and supporting polymers without any specific interactions, the photocatalytic efficiency of TiEPS balls with UV (Kapp =0.016~0.043 min-1) was greater through coupled reaction processes (adsorption, photolysis, and photocatalysis). After 5-min sonication, more TiO₂ powders on the TiEPS balls can be involved into the both adsorption and photocatalytic reactions of MB, and can increase the MB removal efficiencies. TiEPS balls can be reused for several consecutive runs without any significant decrease in photocatalytic activity until the recalcitrant contaminants were completely coated on the surface of TiEPS balls and loss of TiO₂ powders embedded on the surface of TiEPS balls was significant. Based on the aforementioned results, self-floating TiEPS balls manufactured from this simple and cost-effective melting method can be used to remove the organic contaminants and to inhibit the excessive growth of harmful algae in the stagnant water body.

Development of Titanium Dioxide (TiO2)-Embedded Buoyant Photocatalyst Balls Using Expanded Polystyrene

A new immobilization technique of nanoscale TiO₂ powders to expanded polystryrene (EPS) balls with temperature-controlled melting method was developed for mass production, and the characterization of TiO₂ powder-embedded EPS (TiEPS) balls was evaluated. Based on the scanning electron microscope (SEM) images and associated energy-dispersive X-ray spectroscopy (EDX) analysis, the components of intact EPS balls are carbon and oxygen whereas those of TiEPS balls are carbon, oxygen, and titanium, indicating that TiO₂ powders were embedded on the surface of EPS balls. As also evident by the X-ray diffraction (XRD) and FTIR analyses, no significant changes in crystalline structure of TiO₂ powders embedded on the EPS balls were found during the preparation and application processes of TiEPS balls. These characterization results indicated that the patches of TiO₂ powders were soundly impregnated over the surface of EPS balls without the significant changes in crystalline structure of TiO₂ powders and both structural changes and deformation of EPS polymer.

A Study on Development of Freshwater Fish Shelter and Evaluation of Water Quality for the Reduction of Thermal Stress in Shallow Pond

The purpose of this study evaluates the water quality of artificial deep pool (ADP) during the late spring and summer. we monitored the water quality, as pH, dissolved oxygen (DO), temperature and conductivity at two stations (St. 1. open water, St. 2. in the ADP). The water quality in the ADP is very stable, and temperature and DO are lower than the open water (average value; temperature 1.4~3.2°C, DO 2.4~3.6 mg/L). In particular, daily variation of temperature in the open water showed above 4°C, but ADP remained stable. The water quality was analyzed using two-way analysis of variance (ANOVA). The results of the analysis showed difference about temperature, pH, DO, conductivity (two-way ANOVA, p<0.05). The ADP has created an aqua environment in thermal and DO gradients by depth. About 1.2 m, Temperature and DO were sharply decreased. The Rhodeus uyekii is dominant species in pond of this study. The ADP offers optimum water temperature (16.5~18.5°C) to the Rhodeus uyekii about spawning. Consequently, the ADP offers stable habitat than open water for fish and aquatic organisms during the summer. It is also a good shelter for fish from a thermal stress.

Evaluation of 1,1,2-trichloroethylene Removal Efficiency Using Composites of Nano-ZnO Photocatalyst and Various Organic Supports

In this study, the various organic supports (i.e., silicone, acrylonitrile-butadiene-styrene, epoxy, and, butadiene rubber) with great sorption capacity of organic contaminants were chosen to develop nano-ZnO/organic composites (NZOCs) and to prevent the detachment of nano-ZnO particles. The water resistance of the developed NZOCs were evaluated, and the feasibility of the developed NZOCs were investigated by evaluating the removal efficiency of 1,1,2-trichloroethylene (TCE) in the aqueous phase. Based on the results from water-resistance experiments, long-term water treatment usage of all NZOCs was found to be feasible. According to the FE-SEM, EDX, and imaging analysis, nano-ZnO/butadiene rubber composite (NZBC) with various sizes and types of porosity and crack was measured to be coated with relatively homogeneously-distributed nano-ZnO particles whereas nano-ZnO/silicone composite (NZSC), nano-ZnO/ABS composite (NZAC), and nano-ZnO/epoxy composite (NZEC) with poorly-developed porosity and crack were measured to be coated with relatively heterogeneously-distributed nano-ZnO particles. The sorption capacity of NZBC was close to 60% relative to the initial concentration, and this result was mainly attributed to the amorphous structure of NZBC, hence the hydrophobic partitioning of TCE to the amorphous structure of NZBC intensively occurred. The removal efficiency of TCE in aqueous phase using NZBC was close to 99% relative to the initial concentration, and the removal efficiency of TCE was improved as the amount of NZBC increased. These results stemmed from the synergistic mechanisms with great sorption capability of butadiene rubber and superior photocatalytic activities of nano-ZnO. Finally, the removal efficiency of TCE in aqueous phase using NZBC was well represented by linear model (), and the values of NZBC were from 2.64 to 3.85 times greater than those of , indicating that butadiene rubber was found to be the suitable organic supporting materials with enhanced sorption capacity and without inhibition of photocatalytic activities of nano-ZnO.