• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.5
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• pp.458-467
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• 1991

In this paper, the cause of linear prediction error is analysed and the theoretical basis for nomalizing the format bandwidth to 0is given and its validity is verified. The formant and bandwidth in relation to the position of the poles of AR filter are measured for an alaysis of the relation between the pole position and the formant bandwidth. By changing the glottis reflection coefficient to 1. the pole position and the formant bandwidth. By changing the glottis reflection coefficient to 1. the effect of the glottis is eliminated and as the result a new linear preiction coefficients are obtained by normalizing the formant bandwidth of the signal to 0. since these coefficients are symmetrical, the standard deviation is larger than the coefficients with fixed glottis reflection coefficient. The bit rate for speech coding can be reduced by a factor of 2 without any loss of information. Through computer simulation, recognition rate of 96.7% is botained by using the proposed algorithm in recognizing 5 Korean vowels in noisy environment.

• Explosives and Blasting
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• v.27 no.1
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• pp.47-52
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• 2009

Blasting is necessary for excavation processes since more than 70% of korean land is consist of mountains. The vibration and noise accompanied by blasting processes usually bring about public complaints. Blasting patterns are chosen by economical efficiency, stability and construction conveniency. However, there are many alternatives without control to settle the popular complaint. To prevent those alternatives, standard blasting method for design and construction were suggested by MLTM (Ministry of Land, Transport and Maritime Affairs) in 2006. However, standard blasting pattern of MLTM was designed in a lump irrespective of types of rocks. Economical loss may occur by ignoring the characteristics of rocks for the applications to the rocks with low intensity, such as shale, or containing many joint. We deduced some economical progresses by performing test blasting with adjusted drilling spacing and length of burden considering the characteristics of local rock. This paper suggests the start of case studies for different applications. Economic improvement can be expected by applying those results deduced from case studies to design and construction.

• Journal of Sensor Science and Technology
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• v.13 no.6
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• pp.479-487
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• 2004

The prevention of noise induced hearing loss is very important, because there is no treatment for it. There are some kinds of devices for hearing protection, and those are effective in preventing a noise induced hearing loss. However, people often resist the use of hearing protection devices because it is difficult to have a conversation. Therefore, a hearing protection device is must effective not only in hearing protection but also in preserving communication ability. In this paper, we proposed a small acoustic filter for ITE type noise protector to solving the problem about the difficulties of conversation. That is applied a principle of acoustic filters that have been used for a muffler of automobiles, guns, and etc. To find out the sound transmission characteristic at the eardrum, we regarded an acoustic filter and external ear canal as a coupled system. So, we simulated the coupled system with OrCad, and experimented with a designed acoustic filter and a 2 cc coupler which has the same transmission characteristic as the external ear canal has. We confirmed that it is possible to adjustment acoustic transmission characteristics through simulation of electrical model for acoustic filter and external ear and experiments using designed small acoustic filters.

• Journal of the Korean Society for Railway
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• v.20 no.4
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• pp.440-447
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• 2017

Spectrum level for the acoustic roughness of wheels and rail surface should be periodically maintained under the limitation of ISO to reduce rolling noise of railway vehicles. Thus, in maintaining railway track, displacement sensor-based measuring devices are broadly used to measure the surface roughness and to perform spectral analysis. However, these measuring devices cause unexpected measuring errors since the displacement sensors are fixed at moving platforms and the main frame produces pitching motion during measurement. To increase the accuracy of the measured values, this paper has investigated the effects of design variables such as wheel base, additional wheels, and elastic deformation of wheels on the surface roughness and acoustic roughness spectrum.

• The Journal of the Acoustical Society of Korea
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• v.39 no.4
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• pp.237-245
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• 2020

In decades, active sonar, which transmits signals and detects incident signals reflected by underwater targets, has been significantly studied since passive sonar in Anti-Submarine Warfare (ASW) detection performance becomes lowered, as underwater threats become their radiated noise reduced. In general, active sonar using Hull-Mounted Sonar (HMS) adjusts vertical tilt (depression) and sequentially transmits multiple Linear Frequency Modulation (LFM) subpulses which have non-overlapped bands, i. e. 1 kHz ~ 2 kHz, 2 kHz ~ 3 kHz, in order to reduce shadow zones. Recently, however, Generalized SFM (GSFM), which is generalized form of SFM, is proposed, and it is confirmed that subpulses of GSFM have orthogonality among each other depending on setting of GSFM parameters. Hence, in this paper, we applied GSFM to active target detection using HMS to improve the performance by the signal processing gain obtained from enlarged bandwidths of GSFM subpulses compared to those of LFM subpulses. Through simulation, we verified that when the number of subpulses is three, the matched filter gain of GSFM is approximately 5 dB higher than that of LFM.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.2
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• pp.6-13
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• 2017

This study examines the effect of the type and number of orifices in an in-line mixer to improve the mixing performance and pressure loss. Recently, in-line non-power-consuming mixers have been increasingly used to complement mechanical mixers, which have a long dwell time, noise, excessive energy consumption, and high maintenance costs. An in-line mixer with an orifice for efficient mixing in water treatment was examined by numerical analysis using the commercial code FLUENT. The flow characteristics of pressure loss and velocity distribution within the mixer and the mixing efficiency were compared with and without the orifices. The CFD results show that the mixing efficiency was improved, but the pressure loss was increased by the in-line mixer with an orifice. A sensitivity study was also done on the principal parameters.

• Journal of the Korean Magnetics Society
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• v.21 no.5
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• pp.167-173
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• 2011

Underwater static magnetic field signature for the naval ship has been widely used as the detonating source of the influence mine system because it is possible to make an accurate target detection in the near field although the magnetic field falls off relatively fast with distance in comparison with the underwater radiated noise signal. In this paper, we describe the prediction results about the underwater static magnetic field by the ferromagnetic hull, the internal structures and the main on-board equipment for the target vessel using the commercial FEM software. Also we analyze the degaussing effectiveness for the target vessel through the degaussing coils arrangement.

• Journal of Sasang Constitutional Medicine
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• v.33 no.3
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• pp.161-170
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• 2021

Introduction Hand eczema is dermatitis that occurs on the hand and fingers. In this case, the patient had chronic hand eczema that had relapsed for 3 years, worsened for 6 months, and did not improve even with standard dermatological treatment. We report significant improvement of the patient with chronic hand eczema, diagnosed with Soeunmin Greater Yin Symptomatology based on Sasang Constitutional Medicine. Methods We prescribed herbal medicine, Sibimigwanjung-tang(十二味寬中湯), and the western medications were continued throughout the treatment period. To evaluate the treatment progression, we observed objective and subjective symptoms and took pictures of the patient's hands. Results At the first time of the outpatient visit, the patient complained of pain, oozing, scaling and severe itching even though she had taken dermatological medication for over 6 months. After 8 weeks of Korean medicine treatment, most symptoms showed improvement, and after about 47 weeks of treatment, the symptoms maintained 90% improvement even after stopping western medications and herbal medications. Conclusion The patient in this case showed a significant improvement of chronic hand eczema and the improvements have been maintained even stopping western medications and herbal medications during follow-up for 15 weeks. In addition, the patient showed improvement and maintenance of general conditions as well as skin-related symptoms. In this case, we can concern the effect of the Sasang Constitutional Medicine focused on treating the patient's general pathology as well as the patient's chief complaint at chronic hand eczema not responding to standard dermatological treatment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.542-545
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• 2022

Recently, the Act on the Punishment of Severe Disasters has drawn attention to the construction environment. A common way to check the safety management of the construction site is for workers to check the site with their own eyes. However, this method is inevitably affected by the limitations of workers' abilities, resulting in fatigue and reduced work efficiency. For this reason, it cannot be an efficient method. Thus, we intend to help the working environment and construction site safety through this study, by proposing an efficient ICT safety management system that can supplement the above methods. In this paper explain the design of the access management system using RFID and the field information monitoring method through noise sensors and fine dust sensors. In addition, we propose a system that can prevent accidents between heavy equipment and people with a PIR sensor, and prevent safety accidents by grasping the slope of the building being worked through a gyro sensor.

• Journal of the Korean Geotechnical Society
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• v.22 no.5
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• pp.69-81
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• 2006

The micropile, which is a kind of the in-situ manufactured pile with small diameter of $150\sim300mm$, is constructed by installing a steel bar or pipe and injecting grout into a borehole. The application fields of micropile are being gradually expanded in a limited space of down-town area, because the micropile has various advantages with low vibration and noise in method and compact size in machine, etc. Mostly, the micropile has been applied to secure the safety of structures, depending on the increment of bearing capacity and the restraint of displacement. The micropile is expected to be used in various fields due to its effectiveness and potentiality in the future. The model test, focused on the interaction between micropile and soil in this study, was carried out. The micropile is installed in a soil adjacent to footing (concept of 'soil reinforcement'). With the test results and soil deformation analysis, the reinforcement effect (relating to bearing capacity and settlement) was analysed in a qualitative and quantitative manner, respectively. Consequently, it is expected that we nay demonstrate the improvement of an efficiency and application in the design and construction of micropile.