• Journal of Advanced Navigation Technology
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• v.26 no.5
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• pp.319-324
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• 2022

If radio interference occurs or there is no navigation device, radio navigation of high-speed moving object becomes impossible. Nevertheless, if there are multiple ground stations and precise range measurement between the high-speed moving object and the ground station can be secured, it is possible to estimate the position of moving object. This paper proposes a position estimation method using high-precision TDOA measurement generated using TLM signal. In the proposed method, a common error of moving object is removed using the TDOA measurements. The measurements is generated based on TLM signal including SOQPSK PN symbol capable of precise timing synchronization. Therefore, since precise timing synchronization of the system has been performed, the timing error between ground stations has a very small value. This improved the position estimation performance by increasing the accuracy of the measured values. The proposed method is verified through software-based simulation, and the performance of estimated position satisfies the target performance.

• Journal of IKEEE
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• v.28 no.2
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• pp.174-179
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• 2024

In this work, we introduce a complementary metal-oxide semiconductor(CMOS)-based integrated circuit(IC) measurement set-up for quantum computer control and read-out using a cryogenic refrigerator. CMOS circuits have to operate at extremely low temperatures of 3 to 5 K for qubit stability and noise reduction. The existing cryogenic measurement system is liquid helium quenching, which is expensive due to the long-term use of expendable resources. Therefore, we describe a cryogenic measurement system based on a closed cycle refrigerator (CCR) that is cost-free even when using helium gas for long periods of time. The refrigerator capable of reaching 4.7 K was built using a Gifford-Mcmahon(G-M) type cryocooler. This is expected to be a cryogenic refrigerator set-up with excellent price competitiveness.

• Journal of Korean Society of Rural Planning
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• v.30 no.3
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• pp.75-84
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• 2024

This study developed the procedure and method for the accuracy assessment of unmanned boat survey data, based on the reservoir water depth data of Misan Reservoir, measured by the manned and unmanned boats in 2009 by Korea Rural Community Corporation. In the first step, this study devised the method to extract the contour map of NGIS data in AutoCAD to generate easily the reservoir boundary map used to set the survey range of reservoir water depth and to test the survey accuracy. The surveyed data coordinate systems of the manned and the unmanned boat were also unified by using ArcGIS for the standards of accuracy assessment. In the accuracy assessment, the spatial correlation coefficient of the grid maps of the two measurement results was 0.95, showing high pattern similarity, although the average error was high at 78cm. To analyze in more detail assessment, this study generated randomly the 3,250m transverse profile route (PR), and then extracted grid values of water depth on the PR. In the results of analysis to the extracted depth data on PR, the error average difference of the unmanned boat measurements was 73.18cm and the standard deviation of the error was 55cm compared to the manned boat. This study set these values as the standard for the correction value by average shift and noise removal of the unmanned boat measurement data. By correcting the unmanned boat measurements with these values, this study has high accuracy results, the reservoir water depth and surface area curve with R² = 0.97 and the water depth and storage volume curve with R² = 0.999.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.6
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• pp.809-818
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• 2019

Since January 1, 2020, the International Maritime Organization (IMO) has put in place strong regulations to reduce air pollution caused by ships by lowing the upper limit of ship fuel oil sulfur content from 3.5% to 0.5% for ships passing through all sea areas around the world. Although it is important to reduce air pollutants by using fuel oil with low sulfur content, reducing the amount of energy waste through the economic operation of a ship can also help reduce air pollutants. Ships can follow designated routes accurately even under the influence of noise using autopilot systems. However, regardless of their quality, the performance of these systems is af ected by noise; heading angles with added measurement noise from the gyroscope are input into the autopilot system and degrade its performance. A technique to solve these problems reduces noise effects through the application of a Kalman filter, which is widely used in condition estimation. This method, however, cannot completely eliminate the effects of noise. Therefore, to further improve noise removal performances, in this study we propose a better denoising method than the Kalman filter technique by applying a multi-layer perceptron (MLP) in forward direction motion and a Kalman Filter in rotation motion. Simulations show that the proposed method improves forward direction motion by preventing the malfunction of a rudder more so than merely using a Kalman Filter.

• Journal of Environmental Science International
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• v.13 no.1
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• pp.99-107
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• 2004

This research is to determine the level of environmental pollution at a blasting construction area which is the origin of noise, vibration, and suspended particle, and to compare the results with other domestic and international standard data. This experiment is also to find out the effects resulting from blasting construction and to propose a plan that can decrease environmental pollution. The blasting construction area is a factory site which is about one and half million square meter and sewage disposal plant is about ninety thousand square meter. Both were selected as the areas for the tests to be conducted in determination test. The test to determine the level of noise, vibration, and total suspended particle was conducted thirty times around the blasting construction area by comparing measurement results and numerical analysis. However, as the test was not conducted in the laboratory but in the actual blasting construction area, it was not possible to do the test with the same exact conditions each true. Therefore, the test was not ideal as conditions could change from test to test. For the most part, the level of noise was below the standard level of 70dB. Every vibration test was under the standard limitation. For example, a house, 200m away was tested for noise and vibration and the level was found to be under the 0.2 cm/sec which is the standard for specialty designed cultural sites., i.e very low level. Also a buried oil pipeline that was 30m away also marked under 2.0cm/sec which is the norm for an industrial area. However, if there were an oil pipeline under the house, the amount of charging gunpowder per hole should be decreased compared to the amount used in the test. The test result for suspended particles under the standard limitation which is 24hour average 300$\mu\textrm{g}$/㎥ at a distance from blasting wavelength, but at detonator, total suspended particle from the blast origin exceeded the standard limitation. If explosion occurs when it detonates in the hole, most of the energy would be absorbed in the crushing of rocks, but some remaining energy would make noises and vibration inevitable. So the important thing is how to minimize the environmental pollution from the blasting. There should be regulations in order that the standard limitation is not exceeded, and to decrease the environmental pollution from the blasting.

• Journal of the Institute of Electronics and Information Engineers
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• v.49 no.10
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• pp.202-208
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• 2012

Fetal heart rate monitoring is important information to assess fetal well-being. Non-invasive fetal ECG (electrocardiography) can be derived from maternal abdominal signal. And various promising signal processing methods have been introduced to extract fetal ECG from mother's composite abdominal signal. However, non-invasive fetal ECG monitoring still has not been widely used in clinical practice due to insufficient reliable measurement and difficulty of signal processing. In application of signal processing method to extract fetal ECG, it might be lower signal to noise ratio due to time varying white Gaussian noise. In this paper, time varying Kalman smoother is proposed to remove white noise in fetal ECG and its feasibility is confirmed. Wiener process was set as Kalman system model and covariance matrix was modified according to white Gaussian noise level. Modified error covariance matrix changed Kalman gain and degree of smoothness. Optimal covariance matrix according to various amplitude in Gaussian white noise was extracted by 5 channel fetal ECG model, and feasibility of proposed method could be confirmed.

• Proceedings of the KSEE Conference
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• 2006.10a
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• pp.167-184
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• 2006

There is cattle shed and house structure of a country village in the vicinity of the construction site. that is why the environmental effect evaluation on blasting had been done in advance to prevent any harm to those from the work. As the result, it is impossible to apply to the blasting method, and the Super wedge method, a kind of a rock-splitting method which there is no secondary breaking by a breaker of the methods breaking &excavating rock according to the classification of the blasting method by the ministry of construction & transpotation, applied to decrease noise and vibration, and to the work classification, the extent of noise and vibration measured with the instrument only for noise(SC-310c) and with the instrument only for vibration(BLASTMATE) respectively. A drilling, splitting, collecting, loading works at the closest point(about 10m) is barely possible on the consideration of vibration to the result of measurement, but carefulness needs on moving of equipment. On the case of noise, even drilling, collecting, loading work except splitting at the comparatively close point(about 20m) is difficult. So, the method breaking &excavating rock according to the classification of the blasting method by the ministry of construction & transpotation has to apply in consideration of noise level in accordance with the work processing.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.39 no.4
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• pp.269-275
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• 2003

In this paper, We examined auditory threshold and critical ratio of amberjack seriola dumerili, in the Jeju Island coastal waters, to find out hearing ability of the fish. The auditory threshold level, critical ratio and hearing index of amberjack were determinded by conditioning method using a sound coupled with electric shock in the condition of ambient noise or white noise in an experimental water tank. The audio-signals of pure tone and electric shock were from 80 HZ to 800 Hz and DC 7 V, respectively. Values for the critical ratios were calculated in terms of the masked thresholds using the noise projected to stable spectrum levels at all measurement frequencies of background noise. Masking noises were in the spectrum level range of 65 dB∼75 dB $(re 1{\mu}Pa\sqrt{Hz})$. The auditory thresholds of amberjack within the test the frequencies were most sensitive at 300HZ as 94.5 dB. The critical ratios of fishes ranged from 36.4 to 52.8 dB. The noise spectrum level that started masking was about 58∼72 dB within frequencies.

• Journal of Korean Society of Environmental Engineers
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• v.28 no.11
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• pp.1198-1206
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• 2006

We have carried out highway traffic noise prediction and measurement for 10 sites with representative road shapes and structures. A road traffic noise prediction model(NIER('99)) has been developed for environmental impact assessment in Korea. With the fitted regression analysis, the distribution ratio($R^2$) and Pearson correction coefficient(r) was 92.4% and 0.96 in $1^{st}$ floor, 38.7% and 0.66 in $3^{rd}$ floor, 42% and 0.65 in $5^{th}$ floor, 7.5% and 0.27 in $7^{th}$ floor, 28.4% and 0.53 in 10th floor, 35.6% and 0.60 in $13^{th}$ floor, 52.7% and 0.73 in $15^{th}$ floor, respectively. The measured values of the noise level except the 1st floor did not show a good agreement with the predicted noise level in the NIER('99) formula. Also, the NIER('99) formula demonstrated that the measured values weren't reasonably close to the predicted values, indicating the validity and adequacy of the predicted models with the fitted vs residual analysis in the 95% of confidence interval and 95% of predict interval. Using the equal variation on the basis of the residual vs fitted value, there was the significant difference for variation between $3^{rd}$ floor and $15^{th}$ floor except $1^{st}$ floor. The results suggested that the NIER('99) model obtained by the results according to the apartment floor must be improved and developed on the road traffic noise.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.197-200
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• 2008

A GNSS augmentation system provides precise position information using corrected GNSS pseudorange measurements. Common bias errors are corrected by PRC (Pseudorange Correction) between reference stations and a rover. However non-common errors (Ionospheric and Tropospheric noise error) are not corrected. Using position error variance this paper analyzes non-common errors (noise errors) of ionosphere and troposphere wet vapor.