• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.333-334
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• 2016

Recently, with the development of technology for the virtual reality services, the virtual reality technology has been to use various application services. However, because it is difficult to secure a non-Augmented Reality Virtual Reality in this case it has a vision problem that can be fixed in a service only, not removable. In this paper, we propose a technique of application iBeacon signal by applying the technology of the indoor location-based service using a virtual reality system described in iBeacon ensure the mobility in a virtual space, and can detect the collisions with other moving objects.

• Journal of Navigation and Port Research
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• v.45 no.5
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• pp.231-237
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• 2021

Enhancing the performance of maritime wireless communication has been highlighted by the issue of cell planning in the sea area because of lack of an appropriate Propagation Loss Model (PLM). To resolve the cell planning issue in vast sea areas, it was essential to develop the (PLM) matching the intended sea area. However, there were considerable gaps between the prediction of legacy PLMs and field measurement in propagation loss and there was a need to develop the adjusted PLM (A-PLM). Therefore, cell planning was performed on this adjusted model, including modification of the base station's location, altitude, and antenna azimuth to meet the quality objectives. Furthermore, in order to verify the availability of the cell planning, Communication Service Quality Monitoring System (CS-QMS) was developed in the LTE-Maritime project to collect LTE signal quality information from the onboard equipment at regular intervals and to ensure that the service quality was high enough to satisfy the goals in each designated grid. As a result of verification, the success rate of RSRP was 95.7% for the intensive management zone (IMZ) and 96.4% for the interested zone (IZ), respectively.

• Current Optics and Photonics
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• v.3 no.5
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• pp.466-472
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• 2019

A system for continuous-wave coherent Doppler lidar (CW lidar), made up of all-fiber structures and a coaxial transmission telescope, was set up for wind measurement in Hefei (31.84 N, 117.27 E), Anhui province of China. The lidar uses a fiber laser as a light source at a wavelength of $1.55{\mu}m$, and focuses the laser beam on a location 80 m away from the telescope. Using the CW lidar, radial wind measurement was carried out. Subsequently, the spectra of the atmospheric backscattered signal were analyzed. We tested the noise and obtained the lower limit of wind velocity as 0.721 m/s, through the Rayleigh criterion. According to the number of Doppler peaks in the radial wind spectrum, a classification retrieval algorithm (CRA) combining a Gaussian fitting algorithm and a spectral centroid algorithm is designed to estimate wind velocity. Compared to calibrated pulsed coherent wind lidar, the correlation coefficient for the wind velocity is 0.979, with a standard deviation of 0.103 m/s. The results show that CW lidar offers satisfactory performance and the potential for application in wind measurement.

• Journal of Korean Society of Water and Wastewater
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• v.35 no.1
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• pp.15-25
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• 2021

In this study, a method of leakage detection was proposed to locate leak position for a reservoir pipeline valve system using wavelet coherence analysis for an injected pressure wave. An unsteady flow analyzer handled nonlinear valve maneuver and corresponding experimental result were compared. Time series of pressure head were analyzed through wavelet coherence analysis both for no leak and leak conditions. The leak information can be obtained through either time domain reflectometry or the difference in wavelet coherence level, which provide predictions in terms of leak location. The reconstructed pressure signal facilitates the identification of leak presence comparing with existing wavelet coherence analysis.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.4
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• pp.245-250
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• 2022

As location-based services using the Global Navigation Satellite System (GNSS) are diversified, concerns about the vulnerability of GNSS to radio disturbance and deception are also growing. Accordingly, countries that own and operate GNSS, such as the United States, Russia, and Europe, are also developing additional navigation systems that can compensate for GNSS' weaknesses. Among them, an R-Mode system that transmits navigation signals using an infrastructure that transmits differential GNSS (DGNSS) information using signals from the medium frequency band currently in operation is being developed in Europe and Korea. Since 2020, Korea has improved four DGNSS transmission stations, including Chungju, Eocheongdo, Palmido, and Socheongdo, to transmit R-Mode signals and test navigation performance in some parts of the West Sea. In this paper, we intend to establish a testbed for measuring the distance of R-Mode signals currently being transmitted and analyze the results. It is confirmed that the distance measurement performance varies depending on the antenna type, diurnal variation, and propagation path of the signal.

• International journal of advanced smart convergence
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• v.9 no.4
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• pp.1-7
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• 2020

This study is a study on the development of AEBS test scenarios for traffic accidents in Korea, and was compared and analyzed using the Traffic Accident Analysis Program. To ensure the safety of passengers and pedestrians in traffic accidents, the number of cars equipped with ADAS is increasing rapidly at all car manufacturers in each country. For traffic accidents used in this study, the domestic traffic accident database (ACCC) produced by SAMSONG was used. Domestic traffic accidents differ from overseas traffic accidents in terms of road type, signal system, driver's seat location and number of vehicles. ACCC databases, which supplemented and reinforced these differences, built a database based on the PC-CRASH program. In the study, we analyze the types of accidents to develop comparative scenarios for each type of road and collision type of traffic accidents. When the road types of traffic accidents in Korea were divided into five types and the collision types were divided into six, it was confirmed that the most types of FRONT-SIDE crashes appeared at the intersection. It is expected that the frequency of possible traffic accidents and collision types can be predicted according to the road type in the accident database, we that it can be used as an AEBS test scenario development suitable for the domestic road environment.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.1
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• pp.41-49
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• 2021

In electronic warfare, beamforming using multiple antennas is applied for effective transmission of electronic attack signals. In order to perform an electronic attack against multiple threats using the same frequency resource, it is necessary to apply a multi-beam transmission algorithm that has been studied in wireless communication systems. For electronic attacks against multiple threats, this paper presents an MMSE(Minimum Mean-Squared Error) beam-forming technique based on the prior location information of threats and an optimization method for power allocation. In addition, the performance of the proposed method is evaluated and received signals of multiple threats are compared and analyzed.

• Journal of the Korea Institute of Military Science and Technology
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• v.24 no.2
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• pp.165-174
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• 2021

This study describes a method of measurement and verification of array manifold of uniform circular array antenna applicable to multistatic Passive Coherent Location(PCL) system using FM broadcasting. In an environment of outdoor test where FM broadcast signals are scattered, array manifold measurement methods using network analyzer and multi-channel digital receiver are introduced. Also, the descriptions and solutions for the test limits of each measurement method and the considerations affecting the measurement accuracy are presented. In addition, to verify the validity of the measured array manifold, the gain and phase difference were compared with the array manifold data obtained by EM simulation, and the effectiveness and accuracy of the measured array manifolds were compared and analyzed by estimating the direction of arrival of the FM broadcast signal received from the multistatic PCL system.

• Design & Manufacturing
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• v.15 no.4
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• pp.51-56
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• 2021

Piercing is the process of shearing a circular hole in sheet metal, whose high shear force makes it difficult to secure the durability of tools. In addition, uneven clearance between tools due to poor alignment of the piercing punch causes accelerated die wear and breakage of the tool. This study reviewed the feasibility of in-situ determining alignment failure during the piercing process by analyzing the signal deviation of a bolt-type piezo sensor installed inside the tool whose alignment level was controlled. Finite element analysis was performed to select the optimal sensor location on the piercing tool for sensitive detection of process signals. A well-aligned piercing process results in uniform deformation in the circumferential direction, and shearing is completed at a stroke similar to the sheet thickness. Afterward, a sharp decrease in shear load is observed. The misaligned piecing punch leads to a gradual decrease in the load after the maximum shear load. This gradual decrease is due to the progressive shear deformation that proceeds in the circumferential direction after the initial crack occurs at the narrow clearance site. Therefore, analyzing the stroke at which the maximum shear load occurs and the load reduction rate after that could detect the misalignment of the piercing punch in real-time.

• Journal of Positioning, Navigation, and Timing
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• v.11 no.3
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• pp.199-208
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• 2022

Inertial Navigation System (INS)/Global Navigation Satellite System (GNSS) integrated navigation system can be used for land vehicle navigation. When the GNSS signal is blocked in a dense urban area or tunnel, however, the problem of increasing the error over time is unavoidable because navigation must be performed only with the INS. In this paper, Non-Holonomic Constraints (NHC) information is utilized to solve this problem. The NHC may correct some of the errors of the INS. However, it should be noted that NHC information is not applicable to all areas within the vehicle. In other words, the lever arm effect occurs according to the distance between the Inertial Measurement Unit (IMU) mounting position and the NHC effective point, which causes the NHC condition not to be satisfied at the IMU mounting position. In this paper, an INS/GNSS/NHC integrated navigation filter is designed, and this filter has a function to compensate for the lever arm effect. Therefore, NHC information can be safely used regardless of the vehicle's driving environment. The performance of the proposed technology is verified through Monte-Carlo simulation, and the performance is confirmed through experimental test.