• Journal of the Korea Society of Computer and Information
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• v.27 no.5
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• pp.101-107
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• 2022

Modeling and simulation is a technique used for operational verification, performance analysis, operational optimization, and prediction of target systems. Discrete Event System Specification (DEVS) of this representative technology defines models with a strict formalism and stratifies the structures between the models. When the atomic DEVS models operate with an intention different the target system, the simulation may lead to erroneous decision-making. However, most DEVS systems have the exclusion of the model test or provision of the manual test, so developers spend a lot of time verifying the atomic models. In this paper, we propose a script-based automated test system for accurate and fast validation of atomic models in Python-based DEVS. The proposed system uses both the existing method of manual testing and the new method of the script-based testing. As Experimental results in our system, the script-based test method was executed within 24 millisecond when the script was executed 10 times consecutively. Thus, the proposed system guarantees a fast verification time of the atomic models in our script-based test and improves the reusability of the test script.

• Journal of the Korea Society of Computer and Information
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• v.27 no.12
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• pp.209-217
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• 2022

Naval CMS(Combat Management System) is linked to various sensors and weapon equipment and use DDS(Data Distribution Service) for efficient data communication between ICU(Interface Control Unit) Node and IPN(Information Processing Node). In order to use DDS, software in the system communicates in an PUB/SUB(Publication/Subscribe) based on DDS topic. If the DDS messages structure in this PUB/SUB method does not match, problems such as incorrect command processing and wrong information delivery occur in sending and receiving application software. To improve this, this paper proposes a DDS message structure integrity verification method. To improve this, this paper proposes a DDS message structure integrity verification method using a hash tree. To verify the applicability of the proposed method to Naval CMS, the message integrity verification rate of the proposed method was measured, and the integrity verification method was applied to CMS and the initialization time of the existing combat management system was compared and the hash tree generation time of the message structures was measured to understand the effect on the operation and development process of CMS. Through this test, It was confirmed that the message structure verification method for system stability proposed in this paper can be applied to the Naval CMS.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.05a
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• pp.186-188
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• 2021

The architecture named IDPS is a design concept of web-based integrated platform for heterogeneous naval combat system, which accomplishes efficiency(decreasing complexity) of diagnosis process and reduces time to diagnose system. Each type of surface vessel has its own diagnostic processes and applications, and that means it also requires its own diagnostic engineer(inefficiency in human resource management). In addition, man-based diagnostic causes quality issues such as difference approach of log analysis in accordance with engineer skills. Thus In this paper, we designed integrated diagnostic platform named IDPS with simplified common process regardless of type of surface vessel and we reinforced IDPS with status decision algorithm(SDA) that judges current software status of vessel based on gathered lots of logs. It will enable engineers to diagnose system more efficiently and to use more resources in utilizing SDA-analyzed diagnostic results.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.5A
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• pp.631-639
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• 2008

This paper reports the mode shapes of Seohae cable-stayed bridge extracted by TDD technique. In order to record total 72 acceleration points in the vertical direction of the bridge deck, a custom made data acquisition system with LAN communication has been especially developed and a set of ambient vibration tests has been conducted. For the measured acceleration responses, total twenty four mode shapes up to 2Hz has been extracted by TDD technique. The extracted mode shapes include many new modes that have not been identified in the current on-line health monitoring system installed in the bridge. It is confirmed that TDD technique is the most effective in extracting the high resolution mode shapes on a particularly long span bridge.

• Journal of Aerospace System Engineering
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• v.18 no.2
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• pp.56-63
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• 2024

As the safety of unmanned vehicles continues to improve, their usage in urban environments, which are full of obstacles such as buildings, is expected to increase. When numerous unmanned vehicles are operated in such environments, an algorithm that takes into account mutual collision avoidance, as well as static and dynamic obstacle avoidance, is necessary. In this paper, we propose an algorithm that handles task assignment and path planning. To efficiently plan paths, we construct a grid-based map and derive the paths from it. To enable quick re-planning in dynamic environments, we focus on reducing computational time. Through simulation, we explain obstacle avoidance and mutual collision avoidance in small-scale problems and confirm their performance by observing the entire mission completion time (Makespan) in large-scale problems.

• Journal of the Korea Society of Computer and Information
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• v.29 no.3
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• pp.107-116
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• 2024

In this paper, we analyze the performance of MicroVM when running AI applications on an edge computing environment and whether it can replace current container technology and traditional virtual machines. To achieve this, we set up Docker container, Firecracker MicroVM and KVM virtual machine environments on a Raspberry Pi 4 and executed representative AI applications in each environment. We analyze the inference time, total CPU usage and trends over time and file I/O performance on each environment. The results show that there is no significant performance difference between MicroVM and container when running AI applications. Moreover, on average, a stable inference time over multiple trials was observed on MicroVM. Therefore, we can confirm that executing AI applications using MicroVM instead of container or heavy-weight virtual machine is suitable for an edge computing.

• The Journal of the Acoustical Society of Korea
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• v.13 no.6
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• pp.75-82
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• 1994

The ray paths and travel times of sound wave in the ocean depend on the physical properties of the propagating media. Ocean Acoustic Tomography(OAT), which is inversely estimate the travel time variations between fixed sources and receivers the physical properties of the corresponding media can he understood. To apply ocean survey technology by using the OAT, the tomographic procedure requires forward problem that variation of the travel times be identified with the variability of the medium. Also, received signals must be satisfied the necessary conditions of ray path stability, identification and resolution in order for OAT to work. The canonical ocean has been determined based on the historical data and its travel time and ray path are used as reference values. The sound speed of canonical ocean in the East Sea is about 1523 m/s at the surface and 1458 m/s at the sound channel axis(400m). Sound speeds in the East Sea are perturbed by warm eddy whose horizontal extension is more than 100 km with deeper than 200 m in depth scale. In this study, an acoustic source and receiver are placed at the depth above the sound channel axis, 350 m, and are separated by 200 km range. Ray paths are identified by the ray theory methed in a range dependent medium whose sound speeds are functions of a range and depth. The eigenray information obtained from interpolation between the rays bracketing the receiver are used to simulate the received signal by convolution of source signal with the eigenray informations. The source signal is taken as a 400 Hz rectangular pulse signal, bandwidth is 16 Hz and pulse length is 64 ms. According to the analysis of the received signal and identified ray path by using numerical model of underwater sound propagation, simulated signals satisfy the necessary conditions of OAT, applied in the East Sea.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.9C
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• pp.836-841
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• 2002

Packet scheduling is an essential function to guarantee a quality of service by differentiating services in the Internet. Scheduling algorithms that have been suggested so far can be devided into Round-Robin methods and Fair Queueing methods Round-Robin methods have the advantage of high-speed processing through simple implementations, while Fair Queueing methods offer accurate services. Fair queueing algorithms, however, have problems of computational overheads and implementation complexity as their schedulers manage the states of every flow. This paper suggests a new method in which each flow performs the calculation in a distributed way to decide the service order. Our algorithm significantly reduces the scheduler's computational overheads while providing the same level of accuracy with the previous Fair Queueing algorithms.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2003.10a
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• pp.87-90
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• 2003

정밀한 위치결정에 사용되는 GPS는 초기 군사목적을 벗어나 자동차, 선박, 비행기 등의 항법은 물론 측량분야, 지각 및 구조물의 변위 감시, 우주, 통신, 국방 분야 등 매우 광범위한 분야에서 활용되고 있으며, 그 이용도가 급속히 증가하는 추세이다. 그러나 GPS 관측값은 부정오차와 정오차 등 많은 오차를 포함하고 있기 때문에 이를 소거하거나 최소화하여야 한다. GPS 오차는 크게 위성궤도나 위성시간 오차등 위성에 관련된 오차, 수신기 잡음이나 다중경로 등 수신기 관련 오차, 그리고 대류권이나 전리층에 의한 전파 오차로 구분할 수 있다. 이들 오차들은 대부분 차분방법과 수학적 알고리즘에 의해 소거되거나 최소화되지만, 다중경로와 수신기 잡음은 소거하거나 축소할 수 없다. 다중경로는 관측당시의 수신기 주변환경에 따라 바뀌기 때문에 수학적으로 소거할 수 없으며, 수신기 잡음은 수신기 내부의 노이즈로 인하여 발생하기 때문에 소거하기가 상당히 어렵다. 본 연구에서는 다중경로에 의한 GPS 기선변화를 알아보기 위해서 여러 조건하에서 정적 GPS 측량을 실시하였다. 먼저 정확한 좌표를 알고 있는 한 점에 GPS를 설치하고 다른 두 대의 GPS을 임의 점에 설치하였고, 이들 두 GPS 중에 하나의 수신기에 다중경로 환경을 설정하였다 정적 GPS 관측시 기선에 어떠한 변화가 오는 파악하기 위해서 기선처리와 망조정을 통해 기선길이와 좌표값을 산출하였다. 이러한 다중경로 실험은 구조물 모니터링 등 mm 정확도를 요구하는 GPS 측량에 유용하게 사용될 수 있을 것이다.

• Aerospace Engineering and Technology
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• v.13 no.1
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• pp.142-152
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• 2014

This paper analyzes the conjunction events of Korea satellites by year or kind of satellite using CSM, which is provided by JSpOC. If multiple CSM for single conjunction event are available, consistency analysis is performed using minimum range of CSM. And this paper presents the contact analysis results with space objects if there is a radar system in Korea. The effectiveness of Korea's radar system is analyzed by calculating the access time or frequency with space objects. Furthermore, we investigate the radar systems of other space agencies and find the specific parameter depending on the operating environment. Using this information, we define the requirements of radar system, which is appropriate the Korea.