• Water for future
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• v.22 no.4
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• pp.415-415
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• 1989

자연재해연구는 인간.자연환경 관계를 연구하는 학문이다. 금세기초 환경결정론, 환경가능주의, 그리고 인지에 의한 행동과학주의로 연구 Paradigm이 변화.발전되어 오며서 지리학에서도 이러한 이론적 방법론의 바탕위에 인간-자연환경 관계를 설명하려고 노력했다. 1920년대 초 Barrow가 인간생태학 개념을 발표, 1950, 1960년대 이에 영향받은 White, Kate와 Burton 같은 미국의 자연재해지리학자들은 미국에서 홍수재해문제를 인간적응, 특히 "인식"의 역할에 중점을 두어 재해지역에서 자원이용과 이의 관리문제를 연구하였다. 1970년대 들어오면서 재해의 양상, 적응방법등이 연구되고, 또한 적응의 여러 비교연구가 있었으며, 사회성과 관련 사회학적 연구 접근과 다양한 레벨의 케이스 Study 또한 이루어졌다. 오늘날의 자연재해연구는 일반재해연구로 발전하여 핵반응, 각종산업.교통재해, 화학물질 및 환경오염문제, 각종 소음공해, 폭발물 사고 등 참으로 여러 종류의 사회문제가 재해연구의 대상이 되었고, 근래에는 약물중독, 성폭행, 그리고 복잡한 현대사회에서 제기되는 정신질환까지 일종의 재해문제로 다루어 지리학내에서 연구되고 있다. 이와같이 연구의 많은 변환.발전과 함께 처음 Academic한 연구로 시작된 재해문제 연구가 이에 관심을 같는 여러분야 즉, 경제.사회, 심리학자, 토지이용개발자, 보험, 은행, 부동산업자 재해와 관련있는 민간단체, 정부기관, 정책실행기관등이 참여하는 공동연구가 활발히 행하여지고 있다. 최근에는 "세계 자연재해 감소 10개년 계획"이라는 Program을 미국이 주동이 되어 국제적인 기구로 만들어 관심있는 여러국가의 과학자, 재해연구가, Engineer, 정부관계자들이 참여 서로 정보와 지식의 교환, 세계의 개발.재개발에 대한 계획, 재해감소의 교육훈련등 다채로운 Project을 가지고 세계 자연재해 감소를 위하여 공동연구의 노력을 하려는 움직임이다. 세계의 권위있는 재해통계에 의하면 한국이 매년 자연재해로 인하여 100만명당 1,000명이 희생되는 나라로 방글라대시, 이란, 중남미와 페루, 과태말라, 동남아시아의 뉴기니와 나란히 중진개발도상국으로 몇안되는 나라의 하나로 들어있는 것을 볼 때 유감이 아닐수 없다. 우리나라는 하루빨리 이러한 자연재해로부터 아까운 생명과 재산을 잃어버리고 있는 고통과 문제를 해결하려는 민간.정부차원에서 관심을 기울이고 우선 기본적인 연구의 기틀을 마련하는 제도적 장치와 분위기가 아쉽다고 않을 수 없다.와 분위기가 아쉽다고 않을 수 없다.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.7
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• pp.948-955
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• 2017

Currently, porous materials (e.g., mineral wool) are the core materials used in offshore plant panels, but in spite of their superb acoustic performance, these items must be replaced for environmental reasons. A honeycomb structure is widely used throughout the industry because of its high strength-to-weight ratio. However, research in terms of noise and vibration is minimal. An acoustic study should be conducted by taking advantage of honeycomb structures to replace porous materials. In this study, a simulation was performed assuming that a honeycomb panel is a superposition of symmetric mode and antisymmetric mode. Reliability was verified by comparing a simulation results based on a theory with a experimental results, and the possibility of the panel as a core material was evaluated by studying the sound insulation characteristics of a honeycomb. As the panel thickness increased, the coincidence frequency shifted to low frequency. As the angle between horizontal line and oblique wall and cell-size decreases, the sound insulation performance is improved. And as the cell-wall thickness increased, the sound insulation performance improved.

• Journal of Drive and Control
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• v.18 no.1
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• pp.1-8
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• 2021

This paper presents research on methods for the reduction of forklifts' noise level for the increased comfort and safety of its operator. A cooling fan with a high air volume flow rate installed in the forklift acts as an important design parameter which efficiently cools the heat exchanger system, helping to transfer internal heat from the engine room to the outdoors with both transmitted and diffracted opening noises. The cooling fan contributes significantly to both the forklift's emitted sound power and the operator room's noise level, thereby necessitating research on the forklift's reduction of acoustic power level and transmission. A noise analysis for various fan models with a biomimetic design based on eagle-wing geometry was conducted. In addition to the acoustic power generation, the aerodynamic performance of the cooling blade is also strongly influenced by the design of airfoil distribution, thereby requiring optimization. The cooling fans were fabricated and installed in the forklift in order to check the efficacy of the forklift engine's cooling, and the final version of the fan was measured for its ability to lower acoustic power level and cool the engine room. This study explains the aerodynamic and acoustic features of the designed fans with the use of BEM analysis and forklift test results.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.3
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• pp.405-411
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• 2020

Recently, studies on underwater communication, related to the development of underwater resources, disaster monitoring and defense, have been actively carried out. In the design of wireless communication systems, path loss is the most important information to derive a link budget that is required to guarantee communication reliability by calculating received power level for the given communication link. The underwater acoustic channel have different characteristics according to geographical location and relevant environmental factors such as water temperature, depth, wave height, algae, and turbidity. Subsequently, many research institutes aiming to develop underwater acoustic communication systems are researching actively on the underwater acoustic channels in various sea areas. In Korea, however, studies on the path loss of the acoustic channel are still insufficient. Therefore, in this study, the path loss of the acoustic channel are studied based on measurement data of the at-sea experiment conducted at Geohae-do, southern sea of Korea.

• The Journal of the Acoustical Society of Korea
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• v.30 no.2
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• pp.92-99
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• 2011

In Japan, bang machine has been considered to have problems about not only the impact force and frequency response which are different from the real impact sources such as children's jumping and running, but also damage in the wooden structure housing. Therefore, a new impactor for lower impact force to prevent demage in wooden structure housing was developed. The impact ball was adopted as the second standard impact source in JIS A 1418-2 and ISO 140-11. In the present study, floor impact sounds generated by impact ball with drop heights in four floors of mock-up building of Building Research Institute (BRI) similar to typical Japanese wooden structure housing were investigated and also compared to jumping sound. The results show that Impact ball sound dropped at 10 cm to 30 cm was most similar to jumping sound. And The impact sound levels at 250 and 500 Hz were more sensitive to drop height than other lower frequencies. The error that may occur from the difference of height of 10 cm up and down based on the standard drop height caused by the impact ball operated by human hands was approx. 1 dB or less only in its value of characteristic, but it must be carefully taken into Impact ball in the Korea Standard.

• Journal of radiological science and technology
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• v.38 no.4
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• pp.403-410
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• 2015

The purpose of this study was to investigate the problems of a signal to noise ratio measurement using a two region measurement method that is conventionally used when using a multi-channel coil and a parallel imaging technique. As a research method, after calculating the standard SNR using a single channel head coil of which coil satisfies three preconditions when using a two region measurement method, we made comparisons and evaluations after calculating an SNR by using a two region measurement method of which method is problematic because it is used without considering the methods recommended by reputable organizations and the preconditions at the time of using a multi-channel coil and a parallel imaging technique. We found that a two region measurement method using a multi-channel coil and a parallel imaging technique shows the highest relative standard deviation, and thus shows a low degree of precision. In addition, we found out that the difference of SNR according to ROI location was very high, and thus a spatial noise distribution was not uniform. Also, 95% confidence interval through Blend-Altman plot is the widest, and thus the conformity degree with a two region measurement method using the standard single channel head coil is low. By directly comparing an AAPM method, which serves as a standard of a performance evaluation test of a magnetic resonance imaging device under the same image acquisition conditions, an NEMA method which can accurately determine the noise level in a signal region and the methods recommended by manufacturers of a magnetic resonance imaging device, there is a significance in that we quantitatively verified the inaccurate problems of a signal to noise ratio using a two region measurement method when using a multi-channel coil and a parallel imaging technique of which method does not satisfy the preconditions that researchers could overlook.