• Journal of Institute of Control, Robotics and Systems
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• v.6 no.10
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• pp.936-941
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• 2000

Advanced space transportation systems, such as the National Aerospace Plane or an Orbital Transfer Vehicle, have atmospheric maneuvering capabilities. For such vehicles the use of aeroassisted orbital transfer from a high Earth orbit to a low Earth orbit, with unpowered flight in the atmosphere, has the potential for significant fuel savings compared to exoatmospheric Hohmann transfer. However, to exploit the fuel savings that can be achieved by using the Earths atmosphere to reduce the vehicles energy, a guidance law is required, and it must be able to handle large unpredictable fluctuations in atmospheric density, on the order of ${\pm}$50% relative to the 1962 US Standard Atmosphere. In this paper aeroassisted orbital transfer is considered as a differential game, with Nature controlling the atmosphere density to yield a worst case (min-max fuel required) atmosphere, from which the guaranteed playable set boundary are achieved. Inside the playable set, it is guaranteed that the vehicle achieves the optimal atmospheric exit condition for the minimum fuel consumption regardless of the atmospheric density variations.

• Journal of Information Technology and Architecture
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• v.9 no.3
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• pp.253-263
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• 2012

Presented in the paper is a methodology for the distributed simulation of underwater warfare based on standard synthetic environment. In the case of underwater warfare simulation, it is very important to reflect environmental data, such as salinity and temperature. For the reusability and interoperability of environmental data, this paper adopts Synthetic Environmental Data Representation and Interchange Specification (SEDRIS(ISO standard for environmental data)). Although SEDRIS provides various merits as an international standard, applying of SEDRIS has been hindered by its broadness and heaviness. To relieve the difficulties, this paper proposes an efficient procedure to utilize SEDRIS technology for the atmosphere and underwater environment. This paper identifies SEDRIS structure for the atmosphere/underwater structured dimensional grid-based and implements the proposed procedure on the High Level Architecture (HLA) / Run-Time Infrastructure (RTI) to explain the generation of the battlefield in a distributed simulation system.

• Korean Journal of Computational Design and Engineering
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• v.17 no.5
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• pp.353-363
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• 2012

As the distributed simulation system has been developed in the defense modeling and simulation, interoperability among heterogeneous simulators is essential to achieve the objectives of the distributed simulation system. However, the interoperability has been a problem to synchronize synthetic environment among many heterogeneous simulators that utilize different environmental data formats. SEDRIS (Synthetic Environmental Data Representation and Interchange Specification) was initiated to solve the problem of the interoperability. SEDRIS provides a standard mechanism to promote data interchange and reusability, and it represents all environmental things from ocean, land and atmosphere to the universe. Although SEDRIS provides various advantages as a standard environmental data format, applying of SEDRIS has been hindered by its broadness and complexity. The main objective of this paper is to explain application development process to improve SEDRIS usability for the atmosphere and ocean. The developed application of this paper provides auto-generation of SEDRIS data with minimum user's input, and the auto-generated SEDRIS data is also visualized and verified by the application.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.1
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• pp.1-15
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• 2011

Korea Global Atmosphere Watch Center (KGAWC), which is located in Anmyeondo and, belongs to the Korea Meteorological Administration (KMA), measures sulfur hexafluoride ($SF_6$) in every hour since 2007. In this study, $SF_6$ observed in 2007 are discussed. A gas chromatograph-electron capture detector (GC-ECD) with pre-cooled device is applied during the observation, and produced data are qualified by means of periodic calibration with $SF_6$ standard gas made by Korea Research Institute of Standard and Science (KRISS). $SF_6$ has been greatly paid attention since Kyoto protocol because of its high global warming potential(GWP) with 22,200 times of $CO_2$ in the period of 100 years. It is a man-made compound and has been usually used for gas insulation since 1970s and for etching process in the information technology-based industry since 1990. Average mixing ratio of $SF_6$ in 2007 was 6.65 pmol/mol at Anmyeondo. According to the GAW report published in 2008, average mixing ratio of $SF_6$ in the atmosphere is continuously growing. At present, the average mixing ratio of $SF_6$ in the atmosphere is known to be approximately 6.25 pmol/mol at global observatory. $SF_6$ value in Anmyeondo shows 0.40 pmol/mol greater than that of the Mauna Loa observatory in 2007.

• Environmental Analysis Health and Toxicology
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• v.22 no.2 s.57
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• pp.177-184
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• 2007

Gaseous organochlorine pesticides (OCPs : heptachlor epoxide, p, p'-DDE, ${\gamma}-HCH,\;{\alpha}-chlordane,\;{\gamma}-chlordane$ and trans-nonachlor) concentration was measured using PUF high volume sampler from June, 2000 to June, 2002 in the semi-rural atmosphere. The OCPs concentration in atmosphere, which is estimated by the slope (m) of Clausius-Clapeyron equation and phase-transition energy $({\Delta}H)$, was influenced by revolatilization from environmental matrix (soil, water and tree leaves) and a long range transportation of air mass. But the former affected OCPs concentration more than the latter. The degradation rate constants (k) of OCPs calculated using multiple regression analysis and revised standard temperature method were in good agreement each other. The value of k of ${\gamma}-HCH$ was very low as -0.0007, but the range of k of other components were $-0.00l8{\sim}-0.0038$. The half-life $({\tau})$ which was calculated by k of ${\gamma}-HCH$ was 2.6 years-the longest one, but that of heptachlor epoxide was in 0.5 year-the shortest one. $({\tau})\;of\;{\alpha}-chlordane,\;{\gamma}-chlordane$ and trans-nonachlor in technical chlordane was 1.0, 1.1 and 0.7 year respectively.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2005.11a
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• pp.349-350
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• 2005

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.7
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• pp.831-839
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• 2012

In this paper, an exponential model of Korea is proposed to minimize an altitude-error of high-altitude target due to atmosphere refraction at radar system. The relation between surface refractivity and refractivity gradient, which is extracted using the least square fit from the measured data at 7 weather stations, is applied to the exponential model. And in order to verify the proposed model, the altitude-errors for a standard atmosphere, a CRPL(Central Radio Propagation Lab.) exponential model, the proposed model are extracted and analyzed using a ray tracing. As a result, the proposed model can improve the altitude estimation performance of radar compared to conventional atmosphere refractive index models.

• Atmosphere
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• v.19 no.3
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• pp.289-296
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• 2009

Measurements of the three-dimensional water vapor distribution in the atmosphere are important for forecast and analysis of meteorological phenomenon. In this study, two Global Positioning System (GPS) campaign networks were installed in Jeju Island and Kangwon-do to construct the vertical water vapor profile solely based on GPS measurements. We implemented a layer model to get the wet refractivity profile and compared the result with radiosonde measurements. The result showed that the vertical profiles from GPS and radiosonde agree well. The bias, root-mean-square error (RMSE) and standard deviation of GPS wet refractivities compared with radiosonde measurements were in the range of 6.6~11.1 mm $km^{-1}$, 11.9~13.9 mm $km^{-1}$, and 4.3~12.3 mm $km^{-1}$, respectively.

• Proceedings of the KSRS Conference
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• 2005.10a
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• pp.388-391
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• 2005

The characteristics of the total ozone variations measured by the ground-based Brewer Ozone Spectrophotometer and the Total Ozone Mapping Spectrometer (TOMS) over Pohang are statistically examined from January 1994 to December 2004. First of all, in the correlation analysis of the total ozone measured from the Brewer Ozone Spectrophotometer and the TOMS, the correlation coefficient was 0.88 and the used data were 2190. The annual mean value of the total ozone is 311 DU with the standard deviation of 13 DU. The maximum and the minimum value were found in March (343 DU) and in September (282 DU), respectively. It was also revealed that the longest seasonal variation is in Spring (341 DU) and the smallest is in Autumn (283 DU). The time series data of the total ozone indicates that the annual variation is significant and the variations for three months and six months are relatively weak. Finally, the annual mean total ozones in Pohang (Brewer), Seoul (Brewer) and Busan (TOMS) are 312 DU, 324 DU and 304 DU, respectively.

• Corrosion Science and Technology
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• v.16 no.6
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• pp.273-277
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• 2017

Atmospheric corrosion is clearly the most noticeable of all corrosion processes. A tremendous amount of economic losses are caused by atmospheric corrosion. Thus, it is imperative to know the level of atmosphere's aggressiveness or in other words "corrosivity", before designing or planning any corrosion prevention strategy. In Singapore, corrosivity values were not recorded earlier though the process of measurement and recording was prevalent in other countries. With an aim of filling this gap, three test sites were setup at three locations in Singapore to represent marine, industrial and urban atmospheres or their mixtures. Subsequently, corrosivity readings were measured and recorded according to ISO 9223:2012 for the first time in Singapore. Salient atmospheric constituents or parameters like time of wetness (TOW), $Cl^-$, $SO_2$, $NO_2$, $O_3$, and $HNO_3$ were measured at all sites over a period of time to categorize corrosivity of particular atmosphere. The effect of the atmosphere on corrosion of steel, Cu, Al, and Zn has also been investigated and quantified. "Estimated" and "determined" corrosivities were quantified and compared according to ISO 9223 standard. The study data along with final corrosivity measurements will be presented and discussed in the present work.