• 한국기계가공학회지
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• 제21권7호
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• pp.98-104
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• 2022

Circular sawing and milling are general machining processes used for routing fiber-reinforced plastics (FRP). In this study, the productivity and cutting quality of a circular saw and flat endmill were compared. As a result, the productivity of the circular saw was approximately ten times higher than that of the endmill for the same tool life, and the burr size of the circular saw was 14 times smaller than that of the flat-end mill. The spectrogram analysis of the cutting sound also showed that the acoustic emission of the circular saw was more uniform than that of the flat end mill. Circular sawing is thus a more suitable process for the straight cutting of pultrusion FRP than a flat endmill.

• 한국입자에어로졸학회지
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• 제15권4호
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• pp.159-171
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• 2019

The cap-and-trade system against the air pollutants in the Seoul Metropolitan Area (SMA), Korea has been implemented since 2008 and will be implemented other areas in Korea on 2020. In this study, to identify the outcome and effectiveness of the cap-and-trade system in the SMA, (1) the rate of change for NOx and SOx emissions, (2) differences between the real emission and allocated amount, and (3) the status of trading are reviewed. It was found that the NOx and SOx emissions from the sources under the cap-and-trade system decreased in the SMA but the reduction was mainly due to the reduction of fuel usage not related to the system. It was found that the average percentage of annual emission in the SMA to the allocated amount between 2008 and 2018 was 66.9% for NOx and 69.3% for SOx, respectively. It suggests that there was over allocation of the emission amounts. The average trading prices in the SMA were 0.193 $/kg for NOx and 0.128 $/kg for SOx, far lower than those in RECLAIM, 131.942 $/kg and 81.677 $/kg, respectively. It was suggested that (1) the cap system for NOx and SOx emissions should be implemented only for the area with high emission ratio from large point sources, (2) the trade system is not suitable for the effective implementation of the cap system, and (3) Korean government should not allow over allocation in order to ensure sound market function without delaying the introduction of technology.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2003년도 제21회 추계학술대회 논문집
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• pp.271-277
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• 2003

최근 환경 소음이 사회적인 문제로 대두되고 있는 가운데, 생활수준의 향상으로 저소음화에 대한 요구가 증가되고 있는 실정이다. 이와 같이 소음에 관한 일반인들의 관심이 높아지면서 생환주변에서 주요 소음원으로 지적되고 있는 회전기계, 특히 가전제품을 비롯한 유동관련 기계류의 소음을 낮추기 위한 노력이 절실히 요구되고 있다. 본 소평팬에 대한 연구에서는 음압 및 음향인텐시티를 이용하여 소음원을 해석하였다. 이때, 광센서를 이용한 축류형 팬의 동기화가 수행되어졌고, 팬 형상에서 정확한 소음원의 위치를 규명하기 위한 기록시간의 결정이 제안되어졌다. 소음 발생하는 위치를 규명하였고, 지향성 연구를 통하여 축류형 팬의 방사형태를 결정하였으며, 음의 흐름도를 가시화 하였다.

• 설비공학논문집
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• 제17권10호
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• pp.922-929
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• 2005

This paper compared ventilation performance between the sound roof tunnel with flat roof and the sound roof tunnel with gable roof. The ventilation rate of the sound roof tunnel is calculated by natural ventilation rate plus ventilation by vehicle. The roof type is divided by the shape of the roof and the ventilator location on the roof. The results between calculation and CFD on the ventilation rate are almost alike. The ventilation rate on the flat roof is $558.4\;m^3/s$ with mid-ventilator and $496.8\;m^3/s$ with left-right ventilator. The ventilation rate on the gable roof is $653.2\;m^3/s$ with mid-ventilator and $611.6\;m^3/s$ with left-right ventilator. The ventilation rate of soundproof with gable roof is higher than that with flat roof. The ventilation rate and with mid-ventilator is higher than that with left-right ventilator the soundproof roof. Therefore, the ventilation performance of soundproof roof depends on the roof shape and ventilator location on the roof.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2011년도 정기 학술대회
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• pp.419-423
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• 2011

AE는 다른 비파괴 검사방법과 달리 가동 상태에서 구조물의 결함이 발생 및 성장을 검출 할 수 있으며, 연속 검사가 가능하다는 장점으로 인하여 대형 구조물의 안정성 평가에 널리 이용되고 있다. 하지만 AE는 20kHz부터 20MHz 사이에 발생하는 음파를 감지하기 위해 센서를 사용하며, 이 센서의 감도에 따라 결과가 달라질 가능성이 존재한다. 이에 본 연구에서는 STS 304와 SS400 강재에 인장실험을 실시하여, 강재의 균열 신호를 탐지하고자 한다. 인장실험에는 스테인리스강 및 탄소강 시편을 준비하였고, 감도가 다른 센서를 이용하여 동일한 인장실험을 실시하였다. 그리고 균열이 발생하는 13개의 신호 파라미터에 대해 군집분석을 실시하여 4가지 종류의 군집으로 분류하였다. 또한 기무가설을 이용한 통계분석을 통해 두 시험편이 다르지 않다는 것을 증명하였다. 이 결과를 바탕으로 본 실험에서 얻은 Waveform이 재료의 균열신호라는 신뢰성을 확인할 수 있었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회
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• pp.743-748
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• 2010

The stability forecasting of rock slope is more difficult than soil slope because catching the sign of failure in monitoring is not easy and deformation of the rock is small in failure process. But in the rock slope, there is small deformation like crack propagation in rock itself and it accumulates gradually in failure process. If it is possible to detect the small change in the rock slope, we can know the failure time exactly. Because the individual signal is gathered in the acoustic emission monitoring, it is possible to monitoring the slope if many sound signal is accumulated. Detection test of acoustic emission was performed. Uniaxial, two types of bending test, and two plane shear test were done with various cement paste sample. Wave propagation velocity of uniaxial test sample was increased with curing time. Wave Analysis give us the result that there is a AE sign signal before the failure, the AE count is suddenly increased. And frequency level 125kHz before failure is changed to level 200-250kHz after failure. In two plane shear test we can catch the AE signal and can know the failure type from wave shape. Monitoring test site is tunnel slope in Hongcheon but special signal is not collected.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2010년도 춘계학술대회 논문집
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• pp.48-48
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• 2010

Sound quality and NVH-issues(Noise, Vibration and Harshness) of vehicles has become very important for car manufacturers. It is interpreted as among the most relevant factors regarding perceived product quality, and is important in gaining market advantage. The general sound quality of vehicles was gradually improved over the years. However, today the development cycles in the automotive industry are constantly reduced to meet the customers' demands and to react quickly to market needs. In addition, new drive and fuel concepts, tightened ecological specifications, increase of vehicle classes and increasing diversification(increasing market for niche vehicles), etc. challenge the acoustic engineers trying to develop a pleasant, adequate, harmonious passenger cabin sound. Another aspect concerns the general pressure for reducing emission and fuel consumption, which lead to vehicle weight reductions through material changes also resulting in new noise and vibration conflicts. Furthermore, in the context of alternative powertrains and engine concepts, the new objective is to detect and implement the vehicle sound, tailored to suit the auditory expectations and needs of the target group. New questions must be answered: What are appropriate sounds for hybrid or electric vehicles? How are new vehicle sounds perceived and judged? How can customer-oriented, client-specific target sounds be determined? Which sounds are needed to fulfil the driving task, and so on? Thus, advanced methods and tools are necessary which cope with the increasing complexity of NVH-problems and conflicts and at the same time which cope with the growing expectations regarding the acoustical comfort. Moreover, it is exceedingly important to have already detailed and reliable information about NVH-issues in early design phases to guarantee high quality standards. This requires the use of sophisticated simulation techniques, which allow for the virtual construction and testing of subsystems and/or the whole car in early development stages. The virtual, testing is very important especially with respect to alternative drive concepts(hybrid cars, electric cars, hydrogen fuel cell cars), where complete new NVH-problems and challenges occur which have to be adequately managed right from the beginning. In this context, it is important to mention that the challenge is that all noise contributions from different sources lead to a harmonious, well-balanced overall sound. The optimization of single sources alone does not automatically result in an ideal overall vehicle sound. The paper highlights modern and innovative NVH measurement technologies as well as presents solutions of recent NVH tasks and challenges. Furthermore, future prospects and developments in the field of automotive acoustics are considered and discussed.

• International Journal of Control, Automation, and Systems
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• 제1권1호
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• pp.101-110
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• 2003

This paper introduces an identification method for nonlinear models in the form of rule-based Fuzzy-Neural Networks (FNN). In this study, the development of the rule-based fuzzy neural networks focuses on the technologies of Computational Intelligence (CI), namely fuzzy sets, neural networks, and genetic algorithms. The FNN modeling and identification environment realizes parameter identification through synergistic usage of clustering techniques, genetic optimization and a complex search method. We use a HCM (Hard C-Means) clustering algorithm to determine initial apexes of the membership functions of the information granules used in this fuzzy model. The parameters such as apexes of membership functions, learning rates, and momentum coefficients are then adjusted using the identification algorithm of a GA hybrid scheme. The proposed GA hybrid scheme effectively combines the GA with the improved com-plex method to guarantee both global optimization and local convergence. An aggregate objective function (performance index) with a weighting factor is introduced to achieve a sound balance between approximation and generalization of the model. According to the selection and adjustment of the weighting factor of this objective function, we reveal how to design a model having sound approximation and generalization abilities. The proposed model is experimented with using several time series data (gas furnace, sewage treatment process, and NOx emission process data from gas turbine power plants).

• 천문학회보
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• 제42권2호
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• pp.54.1-54.1
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• 2017

Intrinsic alignments (IA), the coherent alignment of intrinsic galaxy orientations, can be a source of a systematic error of weak lensing surveys. The redshift evolution of IA also contains information about the physics of galaxy formation and evolution. We present the first measurement of IA at high redshift, z~1.4, using the spectroscopic catalog of blue star-forming galaxies of the FastSound redshift survey, with the galaxy shape information from the Canada-Hawaii-France telescope lensing survey. The IA signal is consistent with zero with power-law amplitudes fitted to the projected correlation functions for density-shape and shape-shape correlation components, $A_{\delta+}=-0.0040\pm 0.0754$ and $A_{++}=-0.0159\pm 0.0271$, respectively. These results are consistent with those obtained from blue galaxies at lower redshifts (e.g., $A_{\delta+}=0.0035_{-0.0389}^{+0.0387}$ and $A_{++}=0.0045_{-0.0168}^{+0.0166}$ at z=0.51 from the WiggleZ survey), suggesting no strong redshift evolution of IA. The upper limit of the constrained IA amplitude corresponds to a few percent contamination to the weak-lensing shear power spectrum, resulting in systematic uncertainties on the cosmological parameter estimations by $-0.035<\Delta \sigma_8<0.026$ and $-0.025<\Delta \Omega_{\mathrm m}<0.019$.

• 한국물환경학회지
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• 제22권5호
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• pp.807-814
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• 2006

Sapkyo Lake Watershed occupies about 19.3% of total area of Chungnam Province, and it is necessary to make a plan of counter-measure for the maintenance of public waterbody sound as well as to ensure water resources due to urbanization and industrialization in this area so densely populated and excessively developed. Conventionally water quality management has been enforced by concentration-based system which is not considered the carrying capacity of receptors, hence there are no proper measures for the prevention of an excessive pollutant load over a waterbody. So even though emission sources abide by the conventional permission regulation, then the quantity of wastewater is increased continuously and encountered water shortage to use finally. Therefore this research focused on the review of introduction of total water quality management system in Sapkyo Lake watershed to maintain public waterbody sound and to ensure water resources. By doing this research in introduction of the system in advance, it can contribute to establish the methodology on systematic water quality management. Also the application of this system in Sapkyo Lake watershed can promote the sustainable development of the area by harmonizing the environment and regional economy ultimately.