• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.1
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• pp.11-18
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• 2022

In order to improve the accuracy of particle tracking prediction techniques near the Korean Strait, this study compared and analyzed a particle tracking model based on a seawater flow numerical model and a machine learning based on a particle tracking model using field observation data. The data used in the study were the surface drifter buoy movement trajectory data observed in the Korea Strait, prediction data by machine learning (linear regression, decision tree) using the tide and wind data from three observation stations (Gageo Island, Geoje Island, Gyoboncho), and prediciton data by numerical models (ROMS, MOHID). The above three data were compared through three error evaluation methods (Correlation Coefficient (CC), Root Mean Square Errors (RMSE), and Normalized Cumulative Lagrangian Separation (NCLS)). As a final result, the decision tree model had the best prediction accuracy in CC and RMSE, and the MOHID model had the best prediction results in NCLS.

• Journal of the Korean Association of Geographic Information Studies
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• v.8 no.1
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• pp.23-39
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• 2005

As developing satellite communication, the tracking range of the moving objects which move in local area is expanded to the whole world. However previous logistics management system is able to monitor freight which transporting in local area using mobile communication system. In this paper, we propose the reefer container management system that manages the location information and other related information such as temperature, humidity of container using the satellite system. The proposed system consists of three parts; data collector, satellite communication manager, reefer container information manager. And the proposed system uses the moving object index for managing the trajectory of container and tracing the location of container or vessel that is transporting the container, and supports various services such as reefer container and vessel tracking, container control and container statistics to logistic companies like shipper and forwarding agent. And the system can be increasing the quality of container transportation service to the shipper, and it makes the efficient management of reefer container to the shipping company.

• Journal of the Korea Computer Graphics Society
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• v.8 no.2
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• pp.1-7
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• 2002

The fast extraction of the silhouettes of a model is very useful for many applications in computer graphics and animation. In this paper, we present an efficient algorithm to compute a sequence of perspective silhouettes for a polyhedral model from a moving viewpoint. The viewpoint is assumed to move along a trajectory q(t), which is a space curve of a time parameter t. Then, we can compute the time-intervals for each edge of the model to be contained in the silhouette by two major computations: (i) intersecting q(t) with two planes and (ii) a number of dot products. If q(t) is a curve of degree n, then there are at most of n + 1 time-intervals for an edge to be in a silhouette. For each time point $t_i$ we can extract silhouette edges by searching the intervals containing $t_i$ among the computed intervals. For the efficient search, we propose two kinds of data structures for storing the intervals: an interval tree and an array. Our algorithm can be easily extended to compute the parallel silhouettes with minor modifications.

• Spatial Information Research
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• v.23 no.2
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• pp.69-81
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• 2015

If one can infer the residential area of SNS users by analyzing the SNS big data, it can be an alternative by replacing the spatial big data researches which result from the location sparsity and ecological error. In this study, we developed the way of utilizing the daily life activity pattern, which can be found from timeline data of tweet users, to infer the residential areas of tweet users. We recognized the daily life activity pattern of tweet users from user's movement pattern and the regional cognition words that users text in tweet. The models based on user's movement and text are named as the daily movement pattern model and the daily activity field model, respectively. And then we selected the variables which are going to be utilized in each model. We defined the dependent variables as 0, if the residential areas that users tweet mainly are their home location(HL) and as 1, vice versa. According to our results, performed by the discriminant analysis, the hit ratio of the two models was 67.5%, 57.5% respectively. We tested both models by using the timeline data of the stress-related tweets. As a result, we inferred the residential areas of 5,301 users out of 48,235 users and could obtain 9,606 stress-related tweets with residential area. The results shows about 44 times increase by comparing to the geo-tagged tweets counts. We think that the methodology we have used in this study can be used not only to secure more location data in the study of SNS big data, but also to link the SNS big data with regional statistics in order to analyze the regional phenomenon.

• Journal of the Korean association of regional geographers
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• v.22 no.4
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• pp.887-911
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• 2016

The empirical law that transverse dunes migrate inversely with their heights leads logically to the prediction that multiple dune ridges will converse to a single huge dune by merging. This contradicts the existence of the steady state dune fields on the Earth. The recent studies have emphasized dune collisions as a key mechanism to the stability of dunefield. The roles of wind shadow aspect ratio, however, have yet to be fully explored. This research aims to investigate the potential roles of wind shadow aspect ratio in the dynamical behaviors of transverse dune field. The simplified model is established for this, based upon allometric properties of transverse dunes, wind speedup on the stoss slope and sand trapping efficiency. The derived governing equations can be transformed to the zoning criteria and vector field for dune evolution. The dynamics analysis indicates that wind shadow aspect ratios do not produce convergent areas on the behavior space; rather, they just act as one of the factors that affect the trajectories of dune evolution. Though the model cannot represent the stability of dune field, but seem to produce a reasonable exponent for dune spacing-height relations.

• Korean Journal of Remote Sensing
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• v.39 no.3
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• pp.257-268
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• 2023

Sea ice plays an important role in Earth's climate by regulating the amount of solar energy absorbed and controlling the exchange of heat and material across the air-sea interface. Its growth, drift, and melting are monitored on a regular basis by satellite observations. However, low-resolution products with passive microwave radiometer have reduced accuracy during summer to autumn when the ice surface changes rapidly. Synthetic aperture radar (SAR) observations are emerging as a powerful complementary, but previous researches have mainly focused on winter ice. In this study, sea ice drift tracking was evaluated and analyzed using SAR images and tracker with global positioning system (GPS) during late summer-early autumn period when ice surface condition changes a lot. The results showed that observational uncertainty increases compared to winter period, however, the correlation coefficient with GPS measurements was excellent at 0.98, and the performance of the ice tracking algorithm was proportional to the sea ice concentration with a correlation coefficient of 0.59 for ice concentrations above 50%.

• Proceedings of the Korean Society for Agricultural Machinery Conference
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• 2017.04a
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• pp.165-165
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• 2017

모돈은 사육 특성상 제한된 파일롯 공간 안에 장시간 머물기 때문에 과중한 몸무게에 의한 지제 이상, 섭식 등의 불량, 수면상태의 불량 등을 지속적으로 관찰해야 하는 대상이다. 측면에 다수의 초음파 센서를 설치하여 기립의 상태 및 운동 시 몸체 궤적의 특성을 분석하여 종합적으로 모돈의 행동 특성을 정량화 하고자 하였다. 이 과정에서 계측 신호의 값을 대수적으로 비교하는 방식에 한계가 있음을 발견하였고, 이를 해결하고자 10 Hz/Ch 내외의 시계열 상대거리 궤적 신호를 주파수 도메인으로 변경하여 분석을 수행하였다. 일정 주파수에 집중되어 있는 주파수 값의 크기 변화(파워 스펙트럼 밀도)를 기준으로 모돈의 움직임의 정상 상태 유무 판별이 가능하였다. 단, 이러한 분석은 계측 데이터를 일괄 처리 방식으로 분석하는 방법으로 도출이 되었으므로, 계측과 정량 분석을 동시에 수행하기 위한 개선이 필요하였다. 계측 시스템에서 사용한 마이크로 프로세서는 Nucleo-446(STMelectronics, CA, USA)로 180 Mhz의 클럭 속도로 작동하나, 총 100 Hz 내외의 16비트 계측 신호에 대해 추가적으로 FFT 등의 주파수 변환 신호 처리를 수행하기에는 연산 능력이 부족하였다. 한편, 주파수 분석의 주기를 1분 단위로 할 경우 처리해야할 정보의 크기는 $100{\times}60{\times}5{\times}2Byte$ 이므로 1분 내에 해당 연산을 종료할 수 있는 추가의 연산 장치가 필요하였다. 계측과 주파수 도메인 변환 연산을 동시에 수행하기 위하여 1 Ghz의 연산능력을 가진 ARM A9 계열의 초소형 멀티코어 AP인 NanoPi Neo Air(Friendlyarm, Guangzhou, China)을 선정하였다. 4개의 코어를 각각 계측, Median 필터링, Smoothing 연산, FFT 분석에 사용하여 1분 단위, 2분 단위, 5분 단위의 주파수 분석을 동시에 수행하였다. 병렬 연산 라이브러리는 오픈 소스인 MPICH(www.mpich.org)를 이용하였다. 상대적으로 여유있는 자원을 보유하고 코어를 실시간으로 결정하여 다수의 모돈 개체 동시 모니터링을 위한 네트워크 연결 역할을 동시에 수행하도록 하였다. 1주일 내외의 요인 실험 수행 결과, 약 70 Mbyte의 데이터가 축적이 되었으며, 1분 단위, 2분 단위, 5분 단위의 주파수 도메인 변환 후 결과를 동시에 취득할 수 있었다. 일부 주파수 도메인 상의 파워 밀도 값이 모돈의 행동 특성에 분석에 유효한 정보를 제공함을 발견하였다. 모돈사 내 현장 보급이 가능한 초소형 AP와 멀티 코어 기반 병렬 처리 기법을 이용한 현장 진단 시스템 개발 연구를 지속적으로 수행할 것이다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.9
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• pp.731-743
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• 2020

The hypersonic glide vehicle ascends to a high altitude by a rocket booster, separates it from the booster, and glides at a hypersonic speed of Mach 5 or higher at an altitude of about 30~70 km, changing its direction in the atmosphere. Since it moves on an unpredictable flight path rather than a parabolic trajectory, it is difficult to intercept with current missile defense systems. The U.S. conducted HTV-2 and AHW flight tests in the early 2010s to confirm the possibility of hypersonic gliding flights, and recently it has been developing hypersonic glide vehicle systems such as LRHW and ARRW. China has conducted several flight tests of the DF-ZF (WU-14) glide vehicle since 2014 and has been operating it with DF-17 missiles. Russia has conducted hypersonic glide vehicle research since the former Soviet Union, but it has repeatedly failed, and recently it has been successfully tested with the Avangard (Yu-71) glide vehicle mounted on the SS-19 ICBM. In this paper, the characteristics, flight test cases, and development trends of hypersonic glide vehicles developed or currently being developed in the United States, China, Russia, Japan, India, and Europe are reviewed and summarized.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.5
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• pp.382-391
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• 2009

Atmospheric speciated mercury concentrations including total gaseous mercury (TGM) and reactive gaseous mercury (RGM) were measured in Chuncheon from March 2006 to November 2008. Average concentrations were 2.10 ${\pm}$ 1.50 ng/$m^3$ and 3.00 ${\pm}$ 3.14 pg/$m^3$ for TGM and RGM, respectively. RGM concentrations were higher during daytime than nighttime probably because of high photochemical activities. We found that RGM concentration considerably increased as ozone increased when fog occurred, indicating that ozone was the important oxidant for $Hg^0$ in aqueous phase. TGM concentration showed positive correlations with CO and $PM_{10}$ which can transport in long-range, but there was no correlation with $NO_2$. Considering that major source of mercury is combustion process, this result showed that local sources did not significantly impact on TGM concentration in Chuncheon. Five-day backward trajectories were calculated for the samples representing high and low concentrations of TGM, and determined that industrialized area of China including Shenyang and Beijing influenced TGM concentrations in Chuncheon.

• Journal of the Korea Computer Graphics Society
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• v.23 no.3
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• pp.105-113
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• 2017

This paper presents a novel on-line trajectory optimization framework based on automatic time warping, which performs the time warping of a reference motion while optimizing character motion control. Unlike existing physics-based character animation methods where sampling times for a reference motion are uniform or fixed during optimization in general, our method considers the change of sampling times on top of the dynamics of character motion in the same optimization, which allows the character to effectively respond to external pushes with optimal time warping. In order to do so, we formulate an optimal control problem which takes into account both the full-body dynamics and the change of sampling time for a reference motion, and present a model predictive control framework that produces an optimal control policy for character motion and sampling time by repeatedly solving the problem for a fixed-span time window while shifting it along the time axis. Our experimental results show the robustness of our framework to external perturbations and the effectiveness on rhythmic motion synthesis in accordance with a given piece of background music.