• International Journal of Ocean System Engineering
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• v.1 no.2
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• pp.102-109
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• 2011

This paper describes the implementation of a precise underwater navigation solution using a multiple sensor fusion technique based on USBL, GPS, DVL and AHRS measurements for the operation of a remotely operated mine disposal vehicle (MDV). The estimation of accurate 6DOF positions and attitudes is the key factor in executing dangerous and complicated missions. To implement the precise underwater navigation, two strategies are chosen in this paper. Firstly, the sensor frame alignment to the body frame is conducted to enhance the performance of a standalone dead-reckoning algorithm. Secondly, absolute position data measured by USBL is fused to prevent cumulative integration error. The heading alignment error is identified by comparing the measured absolute positions with the DR algorithm results. The performance of the developed approach is evaluated with the experimental data acquired by MDV in the South-sea trial.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.5
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• pp.549-556
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• 2009

One of the basic technology for implementing the autonomy of UGV(Unmanned Ground Vehicle) is a path planning algorithm using obstacle and raw terrain information which are gathered from perception sensors such as stereo camera and laser scanner. In this paper, we propose a generation method of DVGM(Directional Velocity Grid Map) which have traverse speed of UGV for the five heading directions except the rear one. The fuzzy system is designed to generate a resonable traveling speed for DVGM from current patch to the next one by using terrain slope, roughness and obstacle information extracted from raw world model data. A simulation is conducted with world model data sampled from real terrain so as to verify the performance of proposed fuzzy inference system.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 1996.06b
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• pp.13-17
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• 1996

This paper presents animation techniques and issues involved in virtual environments where the participants interact with each other through a network. The state of the participant should be recognized at each local site, and broadcast to the other sites. Because information exchange is minimal, animation techniques are applied to convert the incoming low DOF parameters into high DOF joint angles that completely determine the configuration of the agents at each frame. As a case study, a software system VRLOCO is introduced, which has been developed by the author over the last five years. From a simple stream of body center positions, VRLOCO generates realistic curved path human locomotion in real-time. Based on the heading direction and speed, the locomotion automatically switches among five different primitives: walking, running, lateral stepping, backward stepping, and turnaround. The techniques presented here proved robust and faithful: the algorithm is not sensitive to the noise in the data, and the resulting animation conforms well with the original data.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.6 no.1
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• pp.21-29
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• 1998

The purpose of the present paper is to determine the time required and error tolerance limits for flight data computation. The results of statistical analysis showed that the calculator side computation required about 50 seconds for each question and wind side computation needed about 115 seconds for each question. In case of error tolerance limits, it was found that the error tolerance limit for altitude computation war 90 feet and two knots of interval was recommanded for the speed computation in calculator side, and one degree of interval for heading computation and five knots interval for speed computation in wind side.

• Korean Journal of Agricultural and Forest Meteorology
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• v.8 no.3
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• pp.190-198
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• 2006

Radiation use efficiency (RUE), the amount of biomass produced per unit intercepted photosynthetically active radiation (PAR), constitutes a main part of crop growth simulation models. The objective of the present study was to evaluate the variation of RUE of rice plants under various nitrogen nutritive conditions. from 1998 to 2000, shoot dry weight (DW), intercepted PAR of rice canopies, and nitrogen nutritive status were measured in various nitrogen fertilization regimes using japonica and Tongil-type varieties. These data were used for estimating the average RUEs before heading and the relationship between RUE and the nitrogen nutritive status. The canopy extinction coefficient (K) increased with the growth of rice until maximum tillering stage and maintained constant at about 0.4 from maximum tillering to heading stage, rapidly increasing again after heading stage. The DW growth revealed significant linear correlation with the cumulative PAR interception of the canopy, enabling the estimation of the average RUE before heading with the slopes of the regression lines. Average RUE tended to increase with the increased level of nitrogen fertilization. RUE increased approaching maximum as the nitrogen nutrition index (NNI) calculated by the ratio of actual shoot N concentration to the critical N concentration for the maximum growth at any growth stage and the specific leaf nitrogen $(SLN;\;g/m^2\;leaf\;area)$ increased. This relationship between RUE (g/MJ of PAR) and N nutritive status was expressed well by the following exponential functions: $$RUE=3.13\{1-exp(-4.33NNNI+1.26)\}$$ $$RUE=3.17\{1-exp(-1.33SLN+0.04)\}$$ The above equations explained, respectively, about 80% and 75% of the average RUE variation due to varying nitrogen nutritive status of rice plants. However, these equations would have some limitations if incorporated as a component model to simulate the rice growth as they are based on relationships averaged over the entire growth period before heading.

• Magazine of the Korean Society of Agricultural Engineers
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• v.24 no.4
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• pp.69-79
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• 1982

The objective of this study is to contribute to drainage planning in the most realistic and economical way by establishing the relationship between rice yield reduction and overhead flooding by muddy water of each growth stage of paddy, which is the most important factor in determining optimum drainage facilities. This study was based on the data mainly from the experimental reports of the Office of Rural Development of Korea, Reduction Rate Estimation for Summer Crops, published by Ministry of Agriculture and Forestry of Japan and other related research documenta- tion. The results of this study are summarized as follows 1. Damages by overhead flooding are highest in heading stage and have the tendency of decrease in the order of booting stage, panicle formation stage, tillering stage, and stage just after transplanting. Damages by overhead flooding of each growing stage are as follows: a) It is considered that overhead flooding just after transplanting gives a little influence on plant growth and yield because the paddy has sufficient growth period from floo ding to harvest time. b) Jt is analyzed that according to the equation y=11 12x 0.908 which is derived from this study, damages by overhead flooding during tillering stage for 1, 2, 3 successive days are 11.1 %, 20.9%, and 30.2% respectively. c) Damages by overhead flooding after panicle formation stage are very serious because recovering period is very short after damage and ineffective tillering is much. Acc- ording to the equation y=9. 58x+10. Ol derived from this study, damages by overhead flooding fal 1,2,3,5 successive days are 19.6%, 29.2%, 38.8%, 57.9% respectively. d) Booting stage is the very important period in which young panicle has grown up almost completely and the number of glumous flower is fixed since reduction division takes place in the microspore mother cell and enbryo mother cell. According to the equation y=39. 66x 0.558 derived from this study, damages by overhead floodingfor 0.5, 1, 3, 5 successive days are 26.9%, 39.7%, 72. 2% and 97.4%, respectively. Therefore, damages by overhead flooding is very serious during the hooting stage. e) When ear of paddy emerges, flowering begins on that day or the next day; when paddy flowers, fertilization will be completed 2-3 hours after flowering. Therefore overhead flooding during heading stage impedes flowering and increases sterilizing percentage. From this reason damages of heading stage are larger than that of booting stage. According to the equation y-41 94x 0.589 derived from this study, damages by overhead flooding for 0.5, 1, 3, 5, successive days are 27.9%, 63.1 %, 80.1%, and 100% 2. Considering that temperature of booting stage is higher than that of beading stage and plant height of booting stage is ten centimeters shorter than that of heading stage, booting stage should be taken as a critical period for drainage planning because possi- bility of damage occurrence in booting stage is larger than that of heading stage. There-fore, it is considered that booting stage should be taken as critical period of paddy growth for drainage planning. 3. Overhead flooding depth is different depending on the stage of growth. In case, booting stage is adopted as design stage of growth for drainage planning, it is conside red that the allowable flooding depth for new varieties and general varieties are 70cm and 80cm respectively. 4. Reduction Rate Estimation by Wind and Flood for Rice Planting of the present design criteria for drainage planning shows damage by overhead flooding for 1 to 2, 3 to 4, 5 to 7 consecutive days; damages by overhead flooding varies considerably over several hours and experimental condition of soil, variety of paddy, and climate differs with real situation. From these reasons, damage by flooding could not be estimated properly in the past. This study has derived the equation which shows damages by flooding of each growth stage on an hourly basis. Therefore, it has become possible to compute the exact damages in case duration of overhead flooding is known.

• Korean Journal of Agricultural and Forest Meteorology
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• v.1 no.1
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• pp.72-80
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• 1999

The study was conducted to establish the safe cropping season for direct- seeding on flooded paddy by the analysis of meteorological data(l973~1992, 20 years) from Korea Meteorological Administration. The critical date for early seeding(CDES) at direct- seeding culture on flooded paddy was decided by the appearance date of daily mean air temperature(DMAT) of 15$^{\circ}C$. The optimum heading date(OHD) was the first day when 22$^{\circ}C$ of daily mean air temperature could be kept for 40 days of ripening period after heading, and the critical date of late heading for safe ripening(CDHR) was the last day when 19$^{\circ}C$ of daily mean air temperature could be kept for 40 days after heading. The optimum seeding date(OSD) and the critical date for late seeding(CDLS) could be decided by the accumulated temperature from OHD and CDHR to the appearance dates of necessary temperatures for early, intermediate, and intermediately late maturing varieties. This results can be used for the determination of the safe cropping season of direct-seeding on flooded paddy in each agroclimatic zone. For instance, the OSD appearance date for early maturing variety in Suwon region appeared to be May 11~20 and the CDLS appearance date was May 31~June 7.

• Journal of Auto-vehicle Safety Association
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• v.10 no.2
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• pp.29-35
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• 2018

This paper presents a quantitative evaluation method and result of moving vehicle perception using automotive radar. It is also important to analyze the accuracy of the perception algorithm quantitatively as well as to accurately percept nearby moving vehicles for safe and efficient autonomous driving. In this study, accuracy of the automotive radar-based perception algorithm which is developed based on interacting multiple model (IMM) has been verified via vehicle tests on real roads. In order to obtain experimental data for quantitative evaluation, Long Range Radar (LRR) has been mounted on the front of the ego vehicle and Short Range Radar (SRR) has been mounted on the rear side of both sides. RT-range has been installed on the ego vehicle and the target vehicle to simultaneously collect reference data on the states of the two vehicles. The experimental data is acquired in various relative positions and velocity, and the accuracy of the algorithm has been analyzed according to relative position and velocity. Quantitative analysis is conducted on relative position, relative heading angle, absolute velocity, and yaw rate of each vehicle.

• Korean Journal of Remote Sensing
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• v.16 no.2
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• pp.109-116
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• 2000

This study was carried out to assess the use of RADARSAT data which is C-band with HH polarization for the rice growth monitoring in Korea. Nine time-series data were taken by shallow incidence angle (standard beam mode 5 or 6) during rice growing season. And then, backscattering coefficients ($\sigma$$^{\circ}$) were extracted by calibration process for comparing with rice growth parameters such as plant height, leaf area index(LAI), and fresh and dry biomass. Field experimental data concerned with rice growth were collected 8 times for the ground truth at the study area, Tangjin, Chungnam, Korea. At the beginning of rice growth, backscattering coefficients were ranged from -l6~-l3dB when rice fields were not covered with rice canopy and flooded. At the maximum vegetative stage of rice, backscattering coefficients of the rice field were the highest ranging from -4.4dB~-3.1dB. The temporal variation of backscattering coefficient($\sigma$$^{\circ}$) in rice field was significant in this study. Backscattering coefficient ($\sigma$$^{\circ}$) of rice field was a little bit lower again after heading stage than before. This results show RADARSAT data is promising for rice monitoring.

• Journal of the Korea Institute of Military Science and Technology
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• v.27 no.2
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• pp.189-196
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• 2024

Classification of drones and birds is challenging due to diverse flight patterns and limited data availability. Previous research has focused on identifying the flight patterns of unmanned aerial vehicles by emphasizing dynamic features such as speed and heading. However, this approach tends to neglect crucial spatial information, making accurate discrimination of unmanned aerial vehicle characteristics challenging. Furthermore, training methods for situations with imbalanced data among classes have not been proposed by traditional machine learning techniques. In this paper, we propose a data processing method that preserves angle information while maintaining positional details, enabling the deep learning model to better comprehend positional information of drones. Additionally, we introduce a training technique to address the issue of data imbalance.