• Bulletin of the Korean Space Science Society
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• 2003.10a
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• pp.48-48
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• 2003

A precision orbit determination (POD) system of low Earth orbiter using the GPS dual frequency measurements has been developed. It is an option of KOMPSAT-2 POD process system. In this research, the orbit determination using the real dual frequency carrier phase measurements of the SAC-C satellite was conducted to verify KOMPSAT-2 POD system reliability. The SAC-C satellite is an international cooperative mission between NASA, the Argentine Commission on Space Activities (CONAE), Centre National d'Etudes Spatiales (CNES or the French Space Agency), Instituto Nacional De Pesquisas Espaciais (Brazilian Space Agency), Danish Space Research Institute, and Agenzia Spaziale Italiana (Italian Space Agency). The SAC-C was launched at November 21, 2000. The altitude of SAC-C is 702 km and it carries a TurboRogue III GPS and four high gain antennas developed by the JPL. The receiver is able to generate the dual frequency code and carrier phase data. Double-differenced carrier phase measurements were formed using 25 IGS stations. The data were sampled at 30 seconds interval. Fully dynamic approach was adopted for POD. The POD results were compared with those of JPL using GOA n software. The comparison verifies that deci-meter level 3D position accuracy of low Earth orbiting satellite could be achieved. The POD system has been developed successfully.

• Smart Structures and Systems
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• v.4 no.1
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• pp.1-17
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• 2008

This study proposes a conceptual framework of in-situ vibration tests and analyses for quality appraisal of non-slender, cast-in-place piles with irregular cross-section configuration. It evaluates a frequency index from vibration recordings to a series of impulse loadings that is related to total soil-resistance forces around a pile, so as to assess if the pile achieves the design requirement in terms of bearing capacity. In particular, in-situ pile-vibration tests in sequential are carried out, in which dropping a weight from different heights generates series impulse loadings with low-to-high amplitudes. The high-amplitude impulse is designed in way that the load will generate equivalent static load that is equal to or larger than the designed bearing capacity of the pile. This study then uses empirical mode decomposition and Hilbert spectral analysis for processing the nonstationary, short-period recordings, so as to single out with accuracy the frequency index. Comparison of the frequency indices identified from the recordings to the series loadings with the design-based one would tell if the total soil resistance force remains linear or nonlinear and subsequently for the quality appraisal of the pile. As an example, this study investigates six data sets collected from the in-situ tests of two piles in Taipu water pump project, Jiangshu Province of China. It concludes that the two piles have the actual axial load capacity higher than the designed bearing capacity. The true bearing capacity of the piles under investigation can be estimated with accuracy if the amplitude of impact loadings is further increased and the analyses are calibrated with the static testing results.

• Journal of The Korean Society of Agricultural Engineers
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• v.53 no.6
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• pp.75-84
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• 2011

The objective of this study is to evaluate the hydrologic impacts of climate and land use changes in a rural small watershed. HadCM3 (Hadley Centre Coupled Model, ver.3) A2 scenario and LARS-WG (Long Ashton Research Station - Weather Generator) were used to generate future climatic data. Future land use data were also generated by the CA-Markov (Cellular Automata-Markov) method. The Soil and Water Assessment Tool (SWAT) model was used to evaluate hydrologic impacts. The SWAT model was calibrated and validated with stream flow measured at the Baran watershed in Korea. The SWAT model simulation results agreed well with observed values during the calibration and validation periods. In this study, hydrologic impacts were analyzed according to three scenarios: future climate change (Scenario I), future land use change (Scenario II), and both future climate and land use changes (Scenario III). For Scenario I, the comparison results between a 30-year baseline period (1997~2004) and a future 30-year period (2011~2040) indicated that the total runoff, surface runoff, lateral subsurface runoff, groundwater discharge, and evapotranspiration increased as precipitation and temperature for the future 30-year period increased. The monthly variation analysis results showed that the monthly runoff for all months except September increased compared to the baseline period. For Scenario II, both the total and surface runoff increased as the built-up area, including the impervious surface, increased, while the groundwater discharge and evapotranspiration decreased. The monthly variation analysis results indicated that the total runoff increased in the summer season, when the precipitation was concentrated. In Scenario III, the results showed a similar trend to that of Scenario II. The monthly runoff for all months except October increased compared to the baseline period.

• Journal of Korea Multimedia Society
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• v.17 no.1
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• pp.69-76
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• 2014

It is hard to represent massive terrain data in real-time even using recent graphics hardware. In order to process massive terrain data, mesh simplification method such as continuous Level-of-Detail is commonly used. However, existing GPU-based methods using quad-tree structure such as geometry splitting, produce lots of vertices to traverse the quad-tree and retransmit those vertices back to the GPU in each tree traversal. Also they have disadvantage of increase of tree size since they construct the tree structure using texture. To solve the problem, we proposed GPU-base chunked LOD technique for real-time terrain rendering. We restrict depth of tree search and generate chunks with tessellator in GPU. By using our method, we can efficiently render the terrain by generating the chunks on GPU and reduce the computing time for tree traversal.

• Knowledge Management Research
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• v.10 no.2
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• pp.85-103
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• 2009

Web 2.0, characterized as openness, sharing, and participation, has enabled Internet users to easily generate a variety of contents, and to share them through Web 2.0 services. Knowledge search service (KSS) is positioning itself as one of typical Web 2.0 services. Yet, few studies have sharpened our understanding of users' knowledge sharing behavior in the KSS environment. In order to address this knowledge void, this paper attempts to explore antecedents of their usage behavior in the KSS environment. Typically, they utilize stored knowledge and share their knowledge simultaneously. Considering this characteristic, our study regards service usage intention and knowledge sharing intention as final dependent variables. This study advances a research model based on Bhattacherjee's expectation-confirmation model, which is expanded by incorporating trust belief. Because of the openness of KSS, trust belief is believed to play a critical role in forming users' service usage intention and knowledge sharing intention. Furthermore, this study examines the difference of the antecedents' effects in terms of users' gender. We collected data from 275 respondents who have experience in using KSS. PLS (partial least squares) was employed for the analysis of the data. Analysis results confirm the important role of user satisfaction and trust belief in the formation of users' service usage intention and knowledge sharing intention. More importantly, trust belief has a more salient effect on knowledge service usage intention than user satisfaction. This study also shows the moderating role of users' gender. Finally, this paper provides managerial guidance on strategic planning aimed at improving users' service usage intention and knowledge sharing intention in the KSS environment.

• Journal of Advanced Navigation Technology
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• v.21 no.6
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• pp.601-607
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• 2017

This study performed fault test on global positoining system (GPS) carrier phase measurements, which is a preprocessing step to generate the positioning correction information based on the global navigation satellite system (GNSS) infrastructure. The existing carrier acceleration ramp step test (CARST) method affects the test result by using the mean value to eliminate the receiver clock error. In this regard, this study applied differencing and compared its results with those of the existing CARST. The fault simulation that applied artificial faults to the actual data found that the fault could be detected independently on each satellite when difference method was applied, and the single difference CARST and the double difference CARST produced similar results. The comparison with the existing method using actual data demonstrated the strengths and weaknesses of satellite and station single difference. Nevertheless, it is our understanding that it would require an additional analysis to determine whether the results were affected by the satellite or receiver clock error.

• Journal of Nutrition and Health
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• v.39 no.8
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• pp.841-849
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• 2006

This study compared the nutritional quality of Korean adults's consumption of lunch prepared at home, commercial places, and institutions. The one day food intake data collected via 24-hour recall in the 2001 National Health and Nutrition Survey were analyzed. Individuals with 19-64 years of age were selected (n = 5,756). Sampling weights in the Survey were used to generate nationally representative estimates. Lunch was categorized into three groups according to the place where the lunch was prepared. home, commercial places, and institutions such as schools and work places. Comparison among the three groups was made for 19-39 years old men (n = 1,387) and women (n =1,572) and 40-64 years old men (n = 1,364) and women (1,433), respectively. The lunch prepared away from home contained more calories. The lunch prepared commercially was higher in calories percentages from fat than that prepared either at home or at institutions. Across the age and gender groups, lunch prepared at home contribute a high level of sodium intake. Among individuals with 40-64 years of age, but not those with 19-39 years of age, lunch prepared commercially was as sodium dense as that prepared at home. Among individuals with 19-39 years of age, the sodium density of lunch prepared commercially was about the same as that prepared at institutional food service of which the menus were planned by dieticians. Such differences in nutritional quality among meals prepared at home, commercial places, and institutions should be considered and applied for the content development of nutrition education and policy.

• Journal of Biomedical Engineering Research
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• v.10 no.3
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• pp.253-260
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• 1989

The time domain methods of estimating the attenuation coefficient are generally based on the analysis of statisical properties of the reflected echoes form an attenuating medium. Hence, it is often required to have a large number of data samples in order to obtain a statistically stable estimation result. In the attenuation estimation problem, this means that many different speckle patterns are required in the spatial resolution volume of an attenLlation image. In this paper, by using the fact that the speckle pattern Is sensitive to the point spread function of the ultrasound beam, we suggest a method to generate the statiscally uncorrelated or slightly correlated data samples in a given region by rotating a linear transducer and carrying out lateral scans for all rotating angles. This technique is applied to the entropy method for attenuation estimation proposed recently by the authors where the performance is verified by experiments using a tissue equivalent phantom.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2007.06a
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• pp.754-757
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• 2007

In this paper, we present an implementation and it's real-sea test of an underwater acoustic data communication system, which allows the system to reduce complexity and increase robustness in time variant underwater environments. For easy adaptation to complicated and time-varying environments of the ocean, all-digital transmitter and receiver systems were implemented. For frame synchronization the CAZAC sequence was used, and QPSK modulation/ demodulation method with carrier frequency of 25kHz and a bandwidth of 5kHz were applied to generate 10kbps transmission rate including overhead. To improve transmission quality, we used several techniques and algorithms such as adaptive beamforming, adaptive equalizer, and convolution coding/Viterbi decoding. for the verification of the system performance, measurement of BER has been done in a very shallow water with depth of 8m at JangMok, Geoje. During the experiment, image data were successfully transmitted up to about 7.4km.

• The KIPS Transactions:PartA
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• v.18A no.6
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• pp.249-254
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• 2011

This paper describes an efficient design of the interpolation circuit to generate the luma and chroma sub-pixels for H.264 motion estimation. The circuit based on the proposed architecture does not require any input data buffering and processes the horizontal, vertical and diagonal sub-pixel interpolations in parallel. The performance of the circuit is further improved by simultaneously processing the 1/2-pixel and 1/4-pixel interpolations for luma components and the 1/8-pixel interpolations for chroma components. In order to reduce the circuit size, we store the intermediate data required to process all the interpolations in parallel in the internal SRAM's instead of registers. We described the proposed circuit at register transfer level and verified its operation on FPGA board. We also synthesized the gate-level circuit using 130nm CMOS standard cell library. It consists of 20,674 gates and has the maximum operating frequency of 244MHz. The total number of SPSRAM bits used in our circuit is 3,232. The size of our circuit (including logic gates and SRAM's) is smaller than others and the performance is still comparable to them.