• Journal of Institute of Control, Robotics and Systems
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• v.18 no.10
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• pp.970-976
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• 2012

In this paper, a single LRF has been used to produce a 3D map for the mobile robot navigation. The 2D laser scanners are used for mobile robots navigation, where the laser scanner is applied to detect a certain level of area by the straight beam. Therefore it is limited to the usages of 2D obstacle detection and avoidance. In this research, it is designed to complement a mobile robot system to move up and down a single LRF along the yaw axis. During the up and down motion, the 2D data are stacked and manipulated to build a 3D map. Often a single LRF data are mixed with Gaussian and impulse noises. The impulse noises are removed out by the hybrid median filter designed in this research. The 2D data which are improved by deleting the impulse noises are layered to build the 3D map. Removing impulse noises while preserving the boundary is a main advantages of the hybrid median filter which has been used widely to improve the quality of images. The effectiveness of this hybrid median filter for rejecting the impulse noises has been verified through the real experiments. The performance of the hybrid median filter is evaluated in terms of PSNR (Peak Signal to Noise Ratio) and the processing time.

• International Journal of Aerospace System Engineering
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• v.3 no.1
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• pp.25-29
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• 2016

This paper highlights the performance of an impulse turbine which is a part of turbopump in a liquid rocket first stage engine. The turbopump, currently under development at Korea Aerospace Research Institute, has an impulse type turbine with 12 nozzles and a single rotor. The impulse turbine can archive high specific power with the low gas flow rates. The supersonic impulse turbine with a single rotor can make a simple structure. High-pressure gases are converted into the dynamic energy with flows through the 12 nozzles and drive the rotor to make the power for the pumps. The turbine test was performed in the high-pressured turbine test facility with air gas instead of burned gas. A hydraulic dynamometer was used to absorb the power from the turbine and control the rotational speed and torque. The test points were at several pressure ratios with 7 different rotational speeds. Results showed the efficiency was highest at the design pressure ratio. The efficiency was insensitive to the pressure ratio variation than the rotational speed. It was a typical characteristic in an impulse turbine.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.12
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• pp.1183-1187
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• 2011

In this paper, an optimal FIR (Finite-Impulse-Response) filter is proposed for discrete time-varying state-space models. The proposed filter estimates the current state using measured output samples on the recent time horizon so that the variance of the estimation error is minimized. It is designed to be linear, unbiased, with an FIR structure, and is independent of any state information. Due to its FIR structure, the proposed filter is believed to be robust for modeling uncertainty or numerical errors than other IIR filters, such as the Kalman filter. For a general system with system and measurement noise, the proposed filter is derived without any artificial assumptions such as the nonsingular assumption of the system matrix A and any infinite covariance of the initial state. A numerical example show that the proposed FIR filter has better performance than the Kalman filter based on the IIR (Infinite- Impulse-Response) structure when modeling uncertainties exist.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.05a
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• pp.404-406
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• 2013

An image edge has been utilized as preprocessing procedure in various field such as object detection, object recognition. there are Sobel, Prewitt, Roberts, Laplacian as conventional edge detection methods. existing methods are implement is simple, but edge detection characteristics is insufficient in impulse noise area. Therefore, to compensate the defect of conventional methods, in this paper, an edge detection algorithm using modified mask is proposed.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.3
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• pp.261-265
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• 2013

The purpose of this study was to evaluate noise level exposures at different locations such as the left and right ears of the shooter, control room, waiting soldier location and drill ground. For this study, we visited two military rifle ranges and took measurements with a sound level meter (3M Quest SoundPro TM) at five different locations with values of Peak (dB(A)) and Max (dB(A)). The highest peak value of impulse noise level averaged 150.4 dB(A), ranging from 149.6 to 150.5 dB(A) at both the left and right ear sides. This result was significantly different between both left and right ear side locations and at other locations such as the control room, waiting soldier location, and drill ground (P < 0.001). Frequency of impulse noise exposure level showed that the left ear of shooter had the highest frequency (20 times) at over 150 dB(A). This study confirmed that there is a need for proper controls to reduce the amount of impulse noise exposure at military rifle ranges.

• Journal of Environmental Health Sciences
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• v.39 no.4
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• pp.354-359
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• 2013

Objectives: The purpose of this study was to investigate exposure levels to K2 rifle noise at a military rifle range among soldiers in training, the left and right ears of shooters, and control managers in the day and night times. Methods: For this study, we visited military rifle ranges and measured the noise of a K2 rifle with a sound level meter (3M Quest SoundPro$^{TM}$) at four different locations with values of Peak (dB(A)) and Max (dB(A)). Results: The highest peak value of impulse noise level averaged 150.4 dB(A), ranging from 149.7 to 150.5 dB(A) at the left-ear side. Impulse noise levels in the daytime were also recorded as higher than during the night. This result was significantly different between daytime and nighttime locations, such as soldier training, right ear of shooter, and control manager (P < 0.001). Conclusion: This study confirmed that there is a need for proper management of impulse noise at military rifle ranges.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.959-962
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• 2012

In the process of image acquisition, transmission and storage, image degradation occurs due to various reason, the mainly reason is noise. To restore basic methods used images of impulse noise pollution by SM, AF, CWMF. In this paper, using the modified filter to remove impulse noise. The method consists of detection and noise filtering of the noise signal. For a non-noise signal is intact, the noise signal is filtered according to the algorithm. And then through the simulation is compared with known basic methods, with PSNR as judged by reference.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.765-767
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• 2013

Modern societies need image processing technology as mobile phones, computers and multimedia etc. are supplied, and image signal processing is now applied in many fields. However, images are damaged by impulse noise from various sources; to restore the damaged images from impulse noise standard median filter has been used as a typical method, but it makes errors at edge area lowering image quality. Therefore, in this paper average filter algorithm, in which mask is processed with multiple partition to remove impulse noise, is proposed. Simulation showed that the proposed method is superior in noise removal property to the existing ones.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.770-772
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• 2013

Edges on the images are widely used in preprocessing in various areas including recognition and detection of the object. As generally known edge detection methods, there is a method using mask and these methods are Sobel, Prewitt, Roberts, Laplacian operator and etc. Implementation of these existing edge detection methods is simple. However, when processing the impulse noise added images, the properties of edge detection is not sufficient. Accordingly, in order to compensate for the weakness of existing edge detection methods and to detect strong edges on the images which were damaged by impulse noise, the edge detection algorithm using transformed mask was proposed in this paper.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.7
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• pp.1734-1739
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• 2014

Currently, with the rapid development of the digital age, multimedia-related image devices become popular. However, images are susceptible to corruption in processing image data due to the impulse noise and active researches have been conducted to restore these images. This paper, in order to restore the damaged images in impulse noise environments, suggested an image restoration algorithm which applies weights depending on spatial distance between directionality and pixel by focusing on damaged pixels. Additionally, this algorithm was compared with existing methods by using the PSNR (peak signal to noise ratio) as the objective standard to judge whether there were improved effects.