• Aerospace Engineering and Technology
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• v.4 no.1
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• pp.57-65
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• 2005

Due to the future of a large size satellite like Geo-stationary orbit satellite, KARI has progressed the construction of Large Thermal Vacuum Chamber(LTVC) with Φ8mXL10m, which simulates the orbit environment at space. The space environment can be characterized as very harsh conditions. Once the spacecraft is launched and enters its orbit, the satellite is exposed to this space environment. The continuous exposure to such space environment could cause malfunction of major parts of the spacecraft, which could lead to the failure of the entire mission. Due to the fact that space environment is completely different from that of the ground, the satellite that functioned normally on the ground could show some unexpected malfunction in space environment. For this reason, the performance of the spacecraft must be confirmed under the simulated conditions of the space environment. This document includes LTVC control logic, Interlock by which the LTVC can be controlled more safely and efficiently.

• Spatial Information Research
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• v.20 no.4
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• pp.83-92
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• 2012

Location-based services (LBS) are increasingly popular due to the improvement of geo-positioning capabilities and wireless communication technology. However, in order to enjoy LBS services, a user requesting a query must send his/her exact location to the LBS provider. Therefore, it is a key challenge to preserve user's privacy while providing LBS. To solve this problem, the existing method employs a 2PASS cloaking framework that not only hides the actual user location but also reduces bandwidth consumption. However, 2PASS does not fully guarantee the actual user privacy because it does not take the real user distribution into account. Hence, in this paper, we propose a nearest neighbor query processing algorithm that supports K-anonymity property based on the weighted adjacency graph(WAG). Our algorithm not only preserves the location of a user by guaranteeing k-anonymity in a query region, but also improves a bandwidth usage by reducing unnecessary search for a query result. We demonstrate from experimental results that our algorithm outperforms the existing one in terms of query processing time and bandwidth usage.

• Ocean and Polar Research
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• v.42 no.3
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• pp.179-194
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• 2020

The present study aims to evaluate the effects of satellite-based SST (OSTIA) assimilation on a regional ocean circulation model for the Yellow and East China Seas (YECS), using three different assimilation methods: the Ensemble Optimal Interpolation (EnOI), Ensemble Kalman Filter (EnKF), and 4-Dimensional Variational (4DVAR) techniques, which are widely used in the ocean modeling communities. The model experiments show that an improved initial condition by assimilating the SST affects the seasonal water temperature and water mass distributions of the YECS. In particular, the SST data assimilation influences the temperature structures horizontally and vertically in winter, thereby improving the behavior of the YS warm current water. This is due to the fact that during wintertime the water column is well mixed, which is directly updated by the SST assimilation. The model comparisons indicate that the SST assimilation can improve the model performance in resolving the subsurface structures in wintertime, but has a relatively small impact in summertime due to the strong stratification. The differences among the different assimilation experiments are obvious when the SST was sharply changed due to a typhoon passage. Overall, the EnKF and 4DVAR show better agreement with the observations than the EnOI. The relatively low performance of EnOI under storm conditions may be related with a limitation of EnOI method whereby an analysis is obtained from a number of climatological fields, and thus the typhoon-induced SST changes in short-time scales may not be adequately reflected in the data assimilation.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.33 no.1
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• pp.23-30
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• 2015

A shoreline mapping is essential for describing coastal areas, estimating coastal erosions and managing coastal properties. This study has planned to map the 3D shorelines with the airborne LiDAR(Light Detection and Ranging) data and the KOMPSAT-2 imagery, acquired in Uljin, Korea. Following to the study, the DSM(Digital Surface Model) is generated firstly with the given LiDAR data, while the NDWI(Normalized Difference Water Index) imagery is generated by the given KOMPSAT-2 imagery. The classification method is employed to generate water and land clusters from the NDWI imagery, as the 2D shorelines are selected from the boundaries between the two clusters. Lastly, the 3D shorelines are constructed by adding the elevation information obtained from the DSM into the generated 2D shorelines. As a result, the constructed 3D shorelines have had 0.90m horizontal accuracy and 0.10m vertical accuracy. This statistical results could be concluded in that the generated 3D shorelines shows the relatively high accuracy on classified water and land surfaces, but relatively low accuracies on unclassified water and land surfaces.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.1
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• pp.72-82
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• 2015

In order to effectively and economically apply the previous POM(Princeton Ocean Model) WAD(Wetting And Drying) to the coastal area, the POM WAD was modified such as the water elevation input of tidal harmonics in the open boundaries was included and a CTS(Computing Time Saving) technique was introduced to the model. The modified model was tested to the standing waves in the rectangular bay and the hydraulic experiments for the flow and heat diffusion in the 3D basin. The numerical results showed a good agreement with the analytical solutions of the standing waves and the observed values by the hydraulic experiments, respectively. And also when the modified model with the CTS technique was applied to Gwangyang Bay of Korea, the computing time was decreased by as much as 39.4%.

• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.10
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• pp.1145-1152
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• 2014

The RFID (Radio-Frequency Identification) system is a technology to discern things by radio and an epoch-making new method to improve product management such as distribution, transport, mobilization, inventory control. However, RFID, which uses radio, is at risk for information leakage and falsification due to the vulnerability of security of the communication section. We designed the new authentication protocol by applying the tent map, which is the representative complex systems, to the RFID communication system. A more solid and simple authentication system was designed by applying the initial value sensitivity and irregularity, which are the representative characteristics of the complex system, to the reader and tag of RFID. The purpose of this paper is to verify the usability of the RFID authentication protocol design that uses the nonlinear system shown in this thesis by the new system differentiated from the authentication system that depends on the existing hash function or random numbers.

• Horticultural Science & Technology
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• v.17 no.4
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• pp.467-469
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• 1999

This study was conducted to examine the changes of nutritive substances in the edible potato varieties ('Superior', 'Atlantic', 'Irish Cobbler', 'Dejima') during storage under low temperature condition($4^{\circ}C$, 85-90% RH) from January to May. The items examined in this experiment were moisture, free soluble sugars, starch and vitamin C. The contents of starch and vitamin C decreased with increasing storage period. The rates of decrease in starch and vitamin C contents were high in February and low after that. The contents of moisture and free soluble sugars did not show a constant tendency during storage period. The contents of glucose and fructose were the highest in February and March. Among the four varieties, 'Superior' contained highest vitamin C, free sugar, and moisture, while 'Atlantic' contained the highest starch.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.93-100
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• 2011

A coupled tide-surge model, which has been evaluated the utility in the previous study, is applied for simulating the inundation phenomena. The coupled model system adopts the hydrodynamic module of MIKE21 software, and the study area is identical to the previous study. The only difference is additional detailed areas for simulating inundation. An artificial scenario of a virtual typhoon striking Mokpo coastal zone at spring high tide is simulated. Then the calculated water level corresponds to the extreme high water level(556 cm) for 100 year return period. The result also shows the inundation depth is 50~100 cm not only near the Mokpo Inner Port but also near the Mokpo North Port. Finally, the coastal inundation prediction map is drawn on the basis of inundation simulation results.

• Journal of Soil and Groundwater Environment
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• v.21 no.6
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• pp.192-203
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• 2016

A field investigation was conducted on an aquifer contaminated with trichloroethylene (TCE) for application of in situ reactive zone treatment using nanosized zero-valent iron (NZVI). The aquifer was an unconfined aquifer with a mean hydraulic conductivity of $5.14{\times}10^{-4}cm/sec$, which would be favorable for NZVI injection. Seasonal monitoring of TCE concentration revealed a presence of non-aqueous phase liquid form of TCE near IW (injection well). The hydrochemical data characterized the site groundwater to be a $Ca-HCO_3$ type. The average value of Langelier Saturation Index of the groundwater was -1.33, which implied that the site was favorable for corrosion of NZVI. Dissolved oxygen (DO) concentration varied between 2.5~11.5 mg/L, which indicated that DO would greatly compete with TCE as an electron acceptor. The hydrogeological and hydrochemical characterization reveals that the time around November would be appropriate for NZVI injection when water level and temperature are relatively high and DO concentration is low.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.3
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• pp.321-331
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• 2013

This paper describes the evaluation of shield TBM disc cutter penetration depth in practice. In this study the disc cutter penetration depth used to design the excavation speed of tunnel is reviewed. The characteristics of ground encountered in the investigation site are analysed and evaluated. The shield TBM used in the field is reviewed to verify the applicability of machine in the site. The thrust and torque capacities of each TBM disc cutter are also evaluated. Based on the field data, the excavation volume and speed are re-analysed to evaluate the disc cutter penetration depth used in the design stage. It is clearly found that the design value of disc cutter penetration depth needs to modify when estimation of the TBM capacities in very hard rock formation ($S_c$ >150 MPa).