• 한국음향학회지
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• 제42권6호
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• pp.565-571
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• 2023

사후확인제 도입으로 현장에서의 바닥충격음 성능 측정이 의무화되고, 평가 방법이 변경되었다. 제도 변화에 따른 바닥충격음 성능 변화를 추적하기 위해서는 변경된 평가방법에 따라 중량충격음 특성이 어떻게 나타나는지에 대한 연구가 필요하다. 본 연구에서는 평면과 바닥구조가 동일한 하나의 아파트 건물에 위치한 59세대를 대상으로 충격원 및 평가지표에 따라 단일수치평가량을 결정하는 주파수 대역의 기여율을 분석하였다. 단일수치평가량에 따른 주파수대역별 기여도 산출방법이 상이하여 단순 비교는 어려우나, 사후확인제 도입 이전 평가방법(뱅머신 측정 및 L'_i,Fmax,AW으로 평가)에서는 63 Hz가 미치는 기여율은 평균 80.8 %로 나타났으며, 125 Hz가 미치는 기여율은 평균 19.2 %으로 나타났다. 현행 평가방법(고무공 측정 및 L'_iA,Fmax으로 평가) 에서는 기여율은 50 Hz ~ 80 Hz에서 평균 33.1 %, 100 Hz ~ 160 Hz에서 평균 58.7 %, 200 Hz ~ 315 Hz에서 평균 6.9 %, 400 Hz ~ 630 Hz에서 평균 1.3 %으로, 63 Hz 대역의 기여도가 낮아진 것으로 나타났다. 이 결과는 대상 공동주택에 대한 사례 분석 내용으로, 더 다양한 공동주택에 대한 측정 데이터를 분석할 필요가 있다.

• 한국식품과학회지
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• 제41권6호
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• pp.603-608
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• 2009

이 연구에서는 사과 홍로의 향 성분들을 분석하고 기여도를 평가하였다. 사과는 시중에서 유통 중인 홍로를 선택하여 헤드스페이스를 형성시킨 후 $25^{\circ}C$에서 1시간 보관하여 분석을 실시하였다. 향기의 분석은 먼저 관능검사법으로 사과의 복합향기를 측정하고, GC/FID/Olfactometry를 사용하여 개별향기로 분리하였을 때 복합향기의 향기가 검출되는지 확인한 뒤 GC/MS를 이용하여 향기성분을 분석하였다. 향기성분의 기여도는 향기를 수치화하기 위하여 향기지속 시간과 향기강도를 고려하여 향기 값을 계산하여 평가하였다. 향기성분의 분석과 기여도 평가를 통하여 사과의 향에 영향을 주는 향기유발성분의 기여율(%)을 구할 수 있었다. 그 결과 기여율(%)이 가장 높게 나타난 물질은 acetic acid(23%), 1-hexanol(16%), butyl ethanoate(13%), 2-methyl-butyl butanoate (9%) 등 4개의 물질로 나타났다. 이 물질은 관능검사법으로 평가한 복합향기와도 일치하며 향기평가요원들이 가장 많이 인지한 향기이기도 하다. 이것으로 이 물질이 사과의 향을 결정짓는 중요한 인자로 작용한다는 것을 알 수 있었다. 이 물질의 생성 메커니즘을 파악하게 된다면 새로운 사과의 품종 개발에 있어 주요한 영향을 미칠 것이며 소비자의 구매만족도를 향상시킬 수 있을 것이다.

• 한국철도학회논문집
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• 제12권2호
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• pp.260-266
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• 2009

위험도분석은 철도사고해석에 주로 사용되는 이론이다. 위험도 분석의 목적은 전설공사전체 과정에서 주요사고부 사고요인과 잠재적인 원인 및 기여정도 등을 조사 분석하는 것이다. 본 논문은 건설공사 현장에서 발생하는 사고원인과 패턴을 분석하고 사고빈도와 심각도를 고려한 위험도 지수를 계산하여 상대적인 위험도 평가를 제공하고자 하는 것이다. 이를 기반으로 사고 위험도 지수의 일관성을 유도하고 위험도 평가를 위한 정량적인 기준을 제공하고자 하였다.

• 한국소음진동공학회논문집
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• 제19권4호
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• pp.347-354
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• 2009

Frequency analysis is one of the most useful way to analyze response signal for the purpose of grasping the dynamic characteristics of system through Fourier transformation. Although it is very effective way for frequency analysis, it is hard to analyze out a specific sound or vibration component which is correlated with others. In this thesis, source contribution analysis tool for NI-PXI equipment is developed with LabVIEW using coherences of MISO(multiple-input single-output) model. For the purpose of examining propriety of developed tool, simulation is performed with several correlated signals that have different frequency range. After checking the OCF(ordinary coherence function) and PCF(partial coherence function) of the each signal for concerned frequency domain, an experiment is conducted on an evaporator that cause the principal noise of a refrigerator. This developed tool will be expected to build up more convenient and serviceable measurement system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.694-698
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• 2006

This paper presents an optimal design process using beads on a body panel to improve interior noise of a passenger vehicle. Except modification of structural members, it is difficult to find effective countermeasures that can work for the intermediate frequency range from 100 Hz to 300 Hz which lies between the booming and low medium frequency. In this study, it is a major goal to find additional counter-measures for this intermediate frequency range by performing optimal design of beads on body panels. The proposed method for design optimization consists of 4 sub-steps, that is, a) problem definition, b) cause analysis, c) countermeasure development and d) validation. The objective function is minimization of interior noise level. The major design variables are the geometrical shape of a bead and combination of beads on the critical panels. Sensitivity analysis and optimization are performed according to the predefined process for an optimal design. It is verified that the proposed design decreases the level of noise transfer function above 5 dB.

• 한국안전학회지
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• 제33권5호
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• pp.157-163
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• 2018

This paper describes design improvement to a research rector for safety enhancement using Probabilistic Safety Assessment (PSA). This PSA under reactor design was undertaken to assess the level of safety for the design of a research reactor and to evaluate whether it is probabilistically safe to operate and reliable to use. The scope of the PSA reported here is a Level 1 PSA, which addresses the risks associated with the core damage. The technical objectives of this study were to identify accident sequences leading to core damage and to derive design improvement from the dominant accident sequences through the sensitivity analysis. The AIMS-PSA and FTREX were used for the this PSA of the research reactor. The criterion for inclusion was all sequences with a point estimate frequency greater than a truncation value of 1.0E-14/yr. The final result indicates a point estimate of 6.79E-05/yr for the overall Core Damage Frequency (CDF) attributable to internal initiating events for the research reactor under design. Based on the dominant accident sequences from the PSA, the seven kinds of sensitivity analysis were performed and some design improvement items were derived. When the five methods to improve the safety were all applied to the reactor design and emergency operating procedure, its risk was reduced to about 1.21E-06/yr from 6.79E-05/yr. The contribution of LOCA and LOEP with high CDF were significantly reduced by the sensitivity analysis. The safety of the research reactor was well improved and the risk was reduced than before adapting the design improvement gotten from the sensitivity analysis. The present study indicated that the research reactor has the well-balanced safety in regard to each initiating event contribution to CDF. The PSA methodology is very effective to improve reactor safety in a conceptual design phase and especially, Risk-informed design(RID) is very nice way to find the deficiencies of research reactor under design and to improve the reactor safety by solving them.

• 대한지역사회영양학회지
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• 제13권5호
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• pp.701-712
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• 2008

The purpose of the present study was aimed to identify dish items applicable in developing dish?based food frequency questionnaire (DFFQ) for a hypertension study of Koreans. The 24-hour recall data of 4,401 subjects aged $20{\sim}65$ years from the 2001 Korean National Health and Nutrition Examination Survey were used for the analysis. Logistic regression model was used to identify the nutrient related with hypertension. Energy, fiber, sodium, calcium, carotene, vitamin B1 and vitamin C were associated with hypertension. Selection the top 30 dish items for these seven nutrients was performed based on their degree of contribution in supplying nutrients in terms of the cumulative percent contribution (cPC), as well as on their degree of explanation for between?person variation, in terms of the cumulative regression coefficient (cMRC). Rice supplied 43% of total energy consumption. Korean cabbage and radish kimchi were two major sources of sodium and it also covered the 27% of between person variation of sodium intake. Soybean paste soup and single item of orange?colored fruits supplied 43% of total vitamin C intake for Koreans and it covered the almost 79% of between person variation among the Korean population. Korean cabbage kimchi was the major source of fiber, calcium, sodium, carotene, and vitamin C for Koreans. In summary, the top 30 selected dish items supplying the 78% to 89% of the 7 nutrients. Those items also covered the 79% to 94% of between person variation of the 7 nutrients consumption. Therefore, the selected 30 dish items in each categories of nutrient could be applicable in developing dish based food frequency questionnaire for hypertension study.

• 한국소음진동공학회논문집
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• 제26권1호
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• pp.97-103
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• 2016

The sensitivity of interior noise that the passengers perceive is comparatively high in the train, and structure-borne and air-borne types of noises come into the train. In this paper, to analyze contributions of these noise sources operational transfer path analysis(OTPA) is used. OTPA has some advantages of executing the contribution rates of several sources simultaneously, and in this work, 29 points are measured while running. Transfer functions between reference measurement points and response measurement points are calculated by the singular value decomposition(SVD) and Principal component analysis(PCA) method, and the frequency characteristics of the noise source are successfully derived. Also the interior noise is predicted and compared with measurement data to show the reliability.

• Steel and Composite Structures
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• 제10권4호
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• pp.349-360
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• 2010

Three dimensional free vibrations analysis of functionally graded fiber reinforced cylindrical shell is presented, using differential quadrature method (DQM). The cylindrical shell is assumed to have continuous grading of fiber volume fraction in the radial direction. Suitable displacement functions are used to reduce the equilibrium equations to a set of coupled ordinary differential equations with variable coefficients, which can be solved by differential quadrature method to obtain natural frequencies. The main contribution of this work is presenting useful results for continuous grading of fiber reinforcement in the thickness direction of a cylindrical shell and comparison with similar discrete laminate composite ones. Results indicate that significant improvement is found in natural frequency of a functionally graded fiber reinforced cylinder due to the reduction in spatial mismatch of material properties and natural frequency.

• Smart Structures and Systems
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• 제16권1호
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• pp.213-222
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• 2015

Early detection and precise location of leakage is of great importance for life-cycle maintenance and management of municipal pipeline system. In the past few years, acoustic emission (AE) techniques have demonstrated to be an excellent tool for on-line leakage detection. Regarding the multi-mode and frequency dispersion characteristics of AE signals propagating along a pipeline, the direct cross-correlation technique that assumes the constant AE propagation velocity does not perform well in practice for acoustic leak location. This paper presents an improved cross-correlation method based on wavelet transform, with due consideration of the frequency dispersion characteristics of AE wave and the contribution of different mode. Laboratory experiments conducted to simulate pipeline gas leakage and investigate the frequency spectrum signatures of AE leak signals. By comparing with the other methods for leak location identification, the feasibility and superiority of the proposed method are verified.