• Journal of Korean Society of Transportation
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• v.25 no.2 s.95
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• pp.17-26
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• 2007

Because the prime objective of the current preemption methods at signalized intersections near highway-railroad grade crossings(IHRGCs) is to clear the crossing, secondary objectives such as safe pedestrian crossing time and minimized delay often are given less consideration or are ignored completely during the preemption. Under certain circumstances state-of-the-practice traffic signal preemption strategies may cause serious pedestrian safety and efficiency problems at IHRGCs. An improved transition preemption strategy(ITPS) that is specifically designed to improve intersection performance while maintaining or improving the current level of safety was developed by Cho and Rilett. Even if the new transition preemption strategy improved both the safety and efficiency of IHRGCs, the performance of the strategy is affected by train speed. Understanding the impact of this factor is essential in order to implement ITPS. In this paper, the effects of train speed were analyzed using a VISSIM simulation model which was calibrated to field conditions. It was concluded that the delay is affected more by train speed than the transitional preemption strategy and the safety of the intersection is not affected by train speed once an advanced preemption warning time(APWT) is equal to or greater than 90 seconds.

• Journal of Technology Innovation
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• v.18 no.1
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• pp.123-152
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• 2010

Concept of Open Innovation (OI) has recently prevailed in academia and industry as a model for increase in R&D productivity. This concept which in turn leads to an improvement in R&D investment efficiency has therefore drawn many firms to adopt this new model. And this has been the same for Korean firms since the extensive introduction of the OI concept in the early 2009. Yet, the problem with this is that the Korean firms do not know much about this concept in practice: what causes OI to occur, what the intended purpose of its introduction is, what proper procedures to take for a successful introduction, and so on. Based on LG Chem’s Open Innovation movement case which ignited in the late 2006, this paper answers the questions previously raised. The successful introduction was made possible by taking a proper procedure of change management along with a strong support from its senior management. This paper also identifies how the OI movement, which was a way to introduce new technology from the outside, has acted as a catalyst in forming a cooperative R&D atmosphere in LG Chem, and how the role of OI has transformed into a strategic tool for organization change.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.84-91
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• 2005

For long time, the takeoff and landing control of airship was worked by human handling. With the development of the autonomous control system, the exact controls during the takeoff and landing were required and lots of methods and algorithms were suggested. This paper presents the result of airship take-off and landing by buoyancy control using air ballonet volume change and performance control of pitch angle for stable flight within the desired altitude. For the complexity of airship's dynamics, firstly, simple PID controller was applied. Due to the various atmospheric conditions, this controller didn't give satisfactory results. Therefore, new control method was designed to reduce rapidly the error between designed trajectory and actual trajectory by learning algorithm using an artificial neural network. Generally, ANN has various weaknesses such as large training time, selection of neuron and hidden layer numbers required to deal with complex problem. To overcome these drawbacks, in this paper, the RBFN (radial basis function network) controller developed. The weight value of RBFN is acquired by learning which to reduce the error between desired input output through and airship dynamics to impress the disturbance. As a result of simulation, the controller using the RBFN is superior to PID controller which maximum error is 15M.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.3
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• pp.238-246
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• 2012

Once oil is spilled into marine environment, it experiences various weathering processes among which evaporation is the most dominant process in the initial stage of weathering. This study aimed to elucidate the effects of evaporation on the physicochemical properties of spilled oil using standardized laboratory experiments. Laboratory evaporation process was successfully reproduced using controlled rotary evaporation method. In case of Iranian Heavy crude (IHC), evaporation rate after 48 hours was $29.3{\pm}0.4%$ (n=40, p<0.001). Evaporation was simulated using ADIOS2 weathering model and the result was in agreement with laboratory experiment. Chemical composition changes of petroleum hydrocarbons including alkanes, polycyclic aromatic hydrocarbons (PAHs) and biomarkers by evaporation rate were also analyzed. As oil evaporated, low molecular weight alkanes and PAHs decreased, while biomakers showed conservative characteristics. Among biomarkers, $17{\alpha}(H)$, $21{\beta}(H)$-hopane was used for calculation of weathering rates, which matched with evaporative mass losses. Weathering rate calculation using hopane showed that stranded oils of weathering stage I (28.9%) and mesocosm oil weathering experiment till 5 days (26.5%) were mainly affected by evaporation process.

• Atmosphere
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• v.30 no.2
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• pp.183-193
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• 2020

In this study, Yeongdong cold air damming (YCAD) cases that occur in winters have been selected using automatic weather station data of the Yeongdong region of Korea. The vertical and horizontal scales of YCAD were analyzed using rawinsonde and numerical weather model. YCAD occurred in two typical synoptic patterns such that low pressure and trough systems crossing and passing over Korea (low crossing type: LC and low passing type: LP). When the Siberian high does not expand enough to the Korean peninsula, low pressure and trough systems are likely to move over Korea. Eventually this could lead to surface temperature (3.1℃) higher during YCAD than the average in the winter season (1.6℃). The surface temperature during YCAD, however, was decrease by 1.3℃. The cold air layer was elevated around 120 m~450 m for LP-type. For LC-type, the cold layer were found at less than approximately 400 m and over 1,000 m, which could be thought of combined phenomena with synoptic and local weather forcing. The cross-sectional analysis results indicate the accumulation of cold air on the east mountain slope. Additionally, the north or northeasterly winds turned to the northwesterly wind near the coast in all cases. The horizontal wind turning point of LC-type was farther from the top of the mountain (52.2 km~71.5 km) than that of LP-type (20.0 km~43.0 km).

• Korean Chemical Engineering Research
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• v.43 no.1
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• pp.1-8
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• 2005

In this study, $TiO_2$ powders were prepared by hydro-thermal synthesis with titanium tetra isopropoxide. The prepared $TiO_2$ and the commercial $TiO_2$(P-25, Degussa) were by impregnating $H_2PtCl_6$ solution or the leached solution from the waste catalytic converter of automobile. Modified photocatalysts were analyzed by ICP-AES, UV-DRS, XRD, SEM. And band-gap energy of modified photo-catalyst was found to decreased to 1.76eV and basic structure was changed upon modification by leached solution. Modified photocatalysts were coated on the wallpaper after using mixed solution with adhesive materials(PVC). And then to know the modified photo catalysts tested the reactivity and quantum efficiency in the mixed gas with NO as reactants in the photo catalytic reactor. In the gas phase, photo-catalytic activity of NO was the highest for modified P-25 catalysts(P-25(w)) that P-25(w) was impregnated by leached solution of wasted catalytic converter.

• Atmosphere
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• v.26 no.1
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• pp.111-126
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• 2016

In the numerical weather model, surface properties can be defined by various parameters such as terrain height, landuse, surface albedo, soil moisture, surface emissivity, roughness length and so on. And these parameters need to be improved in the Seoul metropolitan area that established high-rise and complex buildings by urbanization at a recent time. The surface roughness length map is developed from digital elevation model (DEM) and it is implemented to the high-resolution numerical weather (WISE-WRF) model. Simulated results from WISE-WRF model are analyzed the relationship between meteorological variables to changes in the surface roughness length. Friction speed and wind speed are improved with various surface roughness in urban, these variables affected to temperature and relative humidity and hence the surface roughness length will affect to the precipitation and Planetary Boundary Layer (PBL) height. When surface variables by the WISE-WRF model are validated with Automatic Weather System (AWS) observations, NEW experiment is able to simulate more accurate than ORG experiment in temperature and wind speed. Especially, wind speed is overestimated over $2.5m\;s^{-1}$ on some AWS stations in Seoul and surrounding area but it improved with positive correlation and Root Mean Square Error (RMSE) below $2.5m\;s^{-1}$ in whole area. There are close relationship between surface roughness length and wind speed, and the change of surface variables lead to the change of location and duration of precipitation. As a result, the accuracy of WISE-WRF model is improved with the new surface roughness length retrieved from DEM, and its surface roughness length is important role in the high-resolution WISE-WRF model. By the way, the result in this study need various validation from retrieved the surface roughness length to numerical weather model simulations with observation data.

• Korean Journal of Agricultural and Forest Meteorology
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• v.14 no.4
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• pp.189-195
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• 2012

To predict the blooming date of 'Yumyeong' peach trees, the models for flower bud developmental rate (DVR) were constructed. The DVRs were calculated from the demanded times at controlled air temperatures. The branches of 'Yumyeong' peach trees were incubated at three different temperatures of 9.7, 15.2, and $18.9^{\circ}C$. The DVRs were also constructed with blooming dates and air temperatures in the field, collected from 1979 to 2008 at the experimental orchard of National Institute of Horticultural and Herbal Science, Suwon, Korea. All the DVRs increased linearly or exponentially with air temperature. The DVR equations evaluated under controlled air temperatures were y=0.0018x+0.0051 and y=$0.0125e^{0.0603x}$. The DVR equations under field conditions were calculated as y=0.0039x-0.0112 and y=$0.0062e^{0.1512x}$. These DVR equations offer developmental indices and predict the date for blooming with air temperature data. These DVR equations were validated against the blooming data observed in the field. When the blooming dates were calculated with exponential DVR equations and daily air temperature data, the root mean squared errors between the observed and predicted dates were around 2 days. These results suggest that the DVR models are useful to predict the blooming date of 'Yumyeong' peach trees.

• Journal of the Korean Association of Geographic Information Studies
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• v.16 no.4
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• pp.91-105
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• 2013

This study performed an assessment of wave power potential in the Kangwon and Dongnam regions encompassing the East Sea and part of South Sea. Annual electricity production and economic effects of 28 wave energy converters with 750kW capacity were analyzed using significant wave height and peak wave period data(created from the NOAA's NWW3 model) and InVEST software(developed by Stanford University and University of Minnesota). Annual electricity production was estimated to be up to 1,207MWh/year and at least 163MWh/year. The spatial pattern of annual electricity production showed that the sea far from land has higher wave power potential than the sea near coast. The net present value(NPV) of 28 wave energy converters was calculated by considering an operation period of 25 years. When assuming that the electricity produced from wave energy converters is transferred to onshore power plants through underwater cables, the NPV was estimated to be up to 5,883USD(6,600,000KRW) and at least -63,494USD(-71,000,000KRW). In contrast, the NPV increased up to 28,095 USD(31,600,000KRW) when assuming that the electricity is utilized in the Ulleungdo and Dokdo. In addition, it was found that the break-even line of NPV in the East Sea becomes closer towards the land according to the increment of electricity price. The NPV of wave energy converters near the Ulleungdo and Dokdo will be 88,158 USD(99,000,000KRW) if the increment of electricity price is 100KRW.

• Journal of the Korean Chemical Society
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• v.50 no.1
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• pp.14-22
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• 2006

the basic model of chemical reactor using glow discharge, we used cathode discharge cell with vacant cavity in the middle. Currently glow discharge is widely studied as a radiation source or atomization device in atomic spectroscopy and remarkable technological achievements are made through the graft with other analysis devices such as microanalysis and steel analysis.1 Additionally, as the characteristics of basic glow discharge and radiation have been reviewed many times, those results could be used in this experiment.2-3 In 1993, an article regarding the treatment of poisonous gas in the air using low temperature plasma was published. According to this article, if DC Glow Discharge is used under continuous atmospheric flow, poisonous gases such as SO2 and NO can be removed.4 Based on those findings, we designed highly efficient reactor where stable air plasma is composed and all air flow pass the negative glow area passing through the tube. It was observed that the cathode tube type glow discharge developed in this study would be economical, easy to use and could be used as radiation source as well.