• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.5
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• pp.286-291
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• 2014

In this study, novel ultrasonic rotary motor of hexadecagon shape stator was proposed. Stator of the hexadecagon ultrasonic motor was composed of an elastic ring and ceramics. The elastic ring had sixteen sides and sixteen angular points. Eight ceramics were attached on the outer surface of the eight sides of the ring. When rotor of cylindrical shaft was inserted inside of the ring stator, central lines of the sixteen sides of the stator hold the shaft by the slight pressures(frictions). This slight pressure was a preload of the motor and it could be controlled by radius and thickness of the ring. When two sinusoidal voltages which have 90 degree phase difference were applied to each four ceramics, elliptical displacements of inner surface of the ring were obtained. These elliptical displacements of the inner surface rotated the shaft rotor through the frictions. The proposed hexadecagon ultrasonic motor was designed and analyzed by using the finite element method (FEM), depending on materials of the elastic ring. Based on the FEM results, one model of motor which showed maximum displacement at contact points was chosen and fabricated. And characteristics of the motor were compared with simulated results. When the motor was fabricated with these results, EL20ET0.5CT0.5CW2 model showed 115[rpm] speed about input voltage of 60[Vrms] at 65.6[kHz]. And the maximum torque of 6[gfcm] was obtained. From these results, the hexadecagon shaped ultrasonic motor can be used to actuator for optical device which needs detailed position control. Also it can be used to medical and portable device by reducing size and weight.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.32 no.3
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• pp.233-244
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• 2014

Precise Point Positioning (PPP) is an increasingly recognized precisely the GPS/GNSS positioning technique. In order to improve the accuracy of PPP, the error sources in PPP measurements should be reduced as much as possible and the ambiguities should be correctly resolved. The correct ambiguity resolution requires a careful control of residual errors that are normally categorized into random and systematic errors. To understand effects from two categorized errors on the PPP ambiguity resolution, those two GPS datasets are simulated by generating in locations in South Korea (denoted as SUWN) and Hong Kong (PolyU). Both simulation cases are studied for each dataset; the first case is that all the satellites are affected by systematic and random errors, and the second case is that only a few satellites are affected. In the first case with random errors only, when the magnitude of random errors is increased, L1 ambiguities have a much higher chance to be incorrectly fixed. However, the size of ambiguity error is not exactly proportional to the magnitude of random error. Satellite geometry has more impacts on the L1 ambiguity resolution than the magnitude of random errors. In the first case when all the satellites have both random and systematic errors, the accuracy of fixed ambiguities is considerably affected by the systematic error. A pseudorange systematic error of 5 cm is the much more detrimental to ambiguity resolutions than carrier phase systematic error of 2 mm. In the $2^{nd}$ case when only a portion of satellites have systematic and random errors, the L1 ambiguity resolution in PPP can be still corrected. The number of allowable satellites varies from stations to stations, depending on the geometry of satellites. Through extensive simulation tests under different schemes, this paper sheds light on how the PPP ambiguity resolution (more precisely L1 ambiguity resolution) is affected by the characteristics of the residual errors in PPP observations. The numerical examples recall the PPP data analysts that how accurate the error correction models must achieve in order to get all the ambiguities resolved correctly.

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.304-312
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• 2005

Effects of two endocrine disrupters (EDs) , nonylphenol (NP) and diethylhexyl phthalate (DEHP), on the population growth and morphology of two freshwater HABs (harmful algal blooms) , Microcystis aeruginosa and Stephanodiscus hantzschii, which frequently evoked the hazard bloom in an eutrophic lakes and reservoirs worldwide, were examined with seven different concentrations of EDs (0.01, 0.05, 0.1, 1,2, 2.5 and 3 ppm). Even at concentration below 0.01 ppm, NP strongly inhibited the algal growth of both M. aeruginosa and S. hantzschii, regardless of the algal growth phase. Morphologically, the algal cell treated with NP gradually lost green color in cytoplasm, became smaller in cell size, and then, was hardly seen in microscopic field. On the other hand, DEHP employed did not affect two algae at all concentrations, and rather stimulated the growth by about 10% with a treatment at 3.00 ppm compared to control. These results indicate that the continuous input of EDs, DEHP into the natural water system plays a crucial role to enhance or help an outbreak of algal bloom in eutrophic waters.

• KSBB Journal
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• v.8 no.3
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• pp.193-199
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• 1993

To find out the optimum conditions for indigo cell culture in air-lift bioreactor, effects of media composition including nutrients and precursors of the indigo colorants on the cell growth and characteristics of the cell growth under various cultural conditions were analyzed. Optimum cultural conditions were tested and the growth characteristics were analyzed in external and internal loop type air-lift bioreactors during 14-day culture. Better cell growth was obtained when the inoculum size was higher in the range of 0.5∼2.5% packed cell volume tested. In the sucrose concentration of 2 to 4%, the cell growth was better when the sucrose concentration was 4% (w/w) in both types of reactors. Sucrose was used up in the early stage of exponential phase of growth At the optimum concentration of a Precursor tryptophan at 1 U UW was 3.8 g/l in internal loop bioreactor, and 3.5 g/l in external one after 14 days of cultivation. Addition of indole showed negative effect on cell growth of suspension culture in air-lift biorector culture and cell mass of 2.5 g/l and 2.2 g/l were obtained in external and internal loop bioreactor, respectively. Selected inorganic nitrogen source potassium nitrate showed about 110% increase in cell growth than that of control. DCW was 16.34 g/l under optimum conditions during 14-day cultivation in internal loop bioreactor.

• Journal of Korea Water Resources Association
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• v.50 no.1
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• pp.29-35
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• 2017

A vehicle rainfall sensor is made to control the operating speed of wipers depending on rainfall. Therefore this is the apparatus to determine the velocity phase of the wipers roughly based on the amount of rainfall. However, the technology which can judge the size of rainfall amount besides determining speed level of the wipers is developing according to the development of the function of rainfall sensor due to the development of technology. In this study, a rainfall measurement by using light scattering by precipitation particles was used. This measurement is to use light signal reflection from front glass and the bigger particle is the less detection of light by light scattering. The detection area of the rainfall sensor and detection channel were extended sizes to increase the accuracy of the rainfall. Also the W-S-R relational expression was developed by using a relationship between the specific precipitation (R) and the amount of sensor detection (S) when there is speed change of the wipers (W) and an indoor rainfall apparatus was used to convert sensing signal to rainfall. The signal system of vehicle rainfall sensor can be converted to the actual rainfall amount by using this formula and if this is provided to users then the vehicle observation network can produce higher-resolution than actual observation network can be produced.

• Korean Chemical Engineering Research
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• v.56 no.6
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• pp.901-908
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• 2018

Graphite is used as a sample anode active material. However, since the maximum theoretical capacity is limited to $372mA\;h\;g^{-1}$, a new anode active material is required for the development of a high capacity lithium ion battery. The maximum theoretical capacity of Si is $4200mA\;h\;g^{-1}$, which is higher than that of graphite. However, it is not suitable for direct application to the anode active material because it has a volume expansion of 400%. In order to minimize the decrease of the discharge capacity due to the volume expansion, the Si was pulverized by the dry method to reduce the mechanical stress and the volume change of the reaction phase, and the change of the volume was suppressed by coating the carbon layers to the particle size controlled Si particles. And carbon fiber is grown like a thread on the particle surface to control secondary volume expansion and improve electrical conductivity. The physical and chemical properties of the materials were measured by XRD, SEM and TEM, and their electrochemical properties were evaluated. In this study, we have investigated the synthesis method that can be used as anode active material by improving cycle characteristics of Si.

• Korean Chemical Engineering Research
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• v.53 no.6
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• pp.740-745
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• 2015

This study investigated the effect of different collection methods on physical properties of pectin hydrogels in microfluidic synthetic approach. The pectin hydrogels were simply produced by the incorporation of calcium ions dissolved in continuous mineral oil. Then, different collection methods, pipetting, tubing, and settling, for harvesting pectin hydrogels were applied. The settling method showed most uniform and monodispersed hydrogels. In the case of settling, a coefficient of variation was 3.46 which was lower than pipetting method (18.60) and tubing method (14.76). Under the settling method, we could control the size of hydrogels, ranging from $30{\mu}m$ to $180{\mu}m$, by simple manipulation of the viscosity of pectin and volumetric flow rate of dispersed and continuous phase. Finally, according to the characteristics of simple encapsulation of biological materials, we envision that the pectin hydrogels can be applied to drug delivery, food, and biocompatible materials.

• Journal of Life Science
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• v.30 no.4
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• pp.402-409
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• 2020

Nervous necrosis virus (NNV) contains a bi-segmented viral genome, RNA1 (3.4 kb, RdRp), and RNA2 (1.4 kb, capsid protein) in a small particle (25 nm). Despite its extremely compact size, NNV has caused serious damage by infecting approximately 120 fish species worldwide since it was first reported in the late 1980s. In order to minimize the damage caused by NNV infection and develop effective vaccines, it is necessary to understand the intra cellular signaling system according to NNV infection. NNV infection induces cell cycle arrest at the G1 phase via the p53-dependent pathway to use the cellular system for its replication. Otherwise, host cells recognize NNV infection through the RIG-1-like receptor (RLR) signaling pathway to control the virus and infected cells, and then ISGs required for antiviral action are activated via the IFN signaling pathway. Moreover, apoptosis of infected cells is triggered by the unfolded protein response (UPR) through ER stress and mitochondria-mediated cell death. Cell signaling studies on the NNV infection mechanisms are still at an early stage and many pathways have yet to be identified. Understanding the various disease-specific cellular signaling systems associated with NNV infection is essential for rapid and accurate diagnosis and vaccine development.

• Journal of Korean Society on Water Environment
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• v.23 no.6
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• pp.945-950
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• 2007

The stormwater runoff from paved area are highly polluted because of particulate materials as well as metals from various vehicular activities. The Division of Road Maintenance in Ministry of Construction and Transportation was recently developed the Guidelines of Environment-kindly Road Maintenance. It is actually requiring the BMP construction to control the nonpoint source pollution as based on the TMDL program. This research is carried out in order to define the characteristics of stormwater runoff from the toll-gate of highways since 2006, which is actually one of the main pollutant sources of paved areas. This monitoring is the first phase work for establishing the treatment facilities in the toll-gates. The one of the main characteristics from toll-gate runoff is the first flush phenomenon containing lots of sediments and metal compounds at the beginning of a storm event. Usually it is used to determine the size of treatment facilities and to calculate the reduced pollutant mass in the facility. The research results shows that the mean EMC vaules for heavy metals are determined to $274.3{\mu}g/L$ for Cd, $1,273.4{\mu}g/L$ for Cr, $1,822.0{\mu}g/L$ for Cu, $6,504.9{\mu}g/L$ for Fe, $14,930.3{\mu}g/L$ for Pb, and $714.1{\mu}g/L$ for Zn. Also the metal mass loadings from the toll-gates are calculated using EMC, watershed area and storm duration.

• Journal of Life Science
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• v.26 no.2
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• pp.247-252
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• 2016

Cultivated wild ginseng is a widely used dietary supplement and medicinal herb. The aim of this study was to optimize the ginseng using high performance liquid chromatography (HPLC)- charged aerosol detection (CAD) for ginsenoside analysis. CAD measures the physical property of an analyte and responds to almost all non-volatile species, independent of their nature, spectral properties, or particle size. It has become widely employed in pharmaceutical analysis. The cultivated wild ginseng extracts were analyzed for compositions of ginsenosides Rb1, Rd, Rg1, Rf, Re, and Rh1. The optimal analysis condition was set up from an experiment using a gradient. Ten grams of cultivated wild ginseng were extracted with 95% EtOH 100 ml for 24 hr at 80℃. The contents of the 6six major ginsenosides in the cultivated wild ginseng extract were Rb1 (5.48±0.12 mg/g), Rd (5.33±0.14 mg/g), Rg1 (12.80± 0.05 mg/g), Rf (19.08±0.68 mg/g), Re (19.87±0.05 mg/g), and Rh1 (16.47±0.16 mg/g), respectively. HPLC showed that the protopanaxatriol group (Rg1, Rf, Re, Rh1) had more content than the protopanaxadiol group (Rb1, Rd) in cultivated wild ginseng extract. In summary, the ginsenosides were identified with HPLC-CAD analysis, and their presence and quantity imply the importance of quality control, as well as the pharmacological activity of the ginseng root.