• International Journal of Railway
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• 제4권1호
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• pp.19-27
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• 2011

Many studies for improving the railway vehicle's performance and comfort such as speed, weight and noise are currently in progress. Improving the structural characteristics of the vehicle for greater noise insulation is considered important for reducing disturbance due to noise, but measuring transmission loss entails large costs. This study explores an alternative method for estimating and measuring the railway vehicle's transmission loss that involves on applying the numerical analysis coupled with scaled reverberation chamber measurement. The transmission loss measurement using scaled reverberation chamber was performed after the compensation value was found through 1mm thickness(1t) specimen. For numerical analysis, a commercially available acoustics solver VA ONE was used. The proposed method is found to lead to transmission loss measurement comparable to the measurements based on large-scale reverberation chamber. Thus, it can be argued that a reliable method has been developed for measuring railway vehicle's transmission loss.

• 한국소음진동공학회논문집
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• 제21권10호
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• pp.967-974
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• 2011

The direct and indirect PFBEM(power flow boundary element method) for the treatment of the 3 dimensional multi-domain problems are proposed to predict the acoustic energy density in medium to high frequency ranges. In the proposed method, the equation is derived in a matrix form by considering coupled relationships of the power flow at the interface of given domains. The proposed method can successfully obtain the analytical solutions for the problems of coupled cubes and the small-scale reverberant chamber. Then the experiment is carried out to obtain STL(sound transmission loss) by using small-scale reverberant chamber and the results are compared with analysis results.

• 한국자동차공학회논문집
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• 제8권5호
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• pp.86-95
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• 2000

A modified spray impingement model has been developed, which is assessed against experiments for the impinging sprays on the small combustion chamber at various gas pressures. To investigate spray behaviors in the diesel combustion chamber, a transparent constant-volume chamber is made which is similar to the combustion chamber of the real diesel engine. The chamber is pressurized by N2 gas from 0 bar to 20 bar to find the effects of ambient pressures. The behaviors of spray injected into this chamber and dispersed after impingement on the cylinder wall is measured two-dimensionally using laser sheet Mie scattering method. The physical submodels have been properly modified to improve the prediction capability of original KIVA code to describe the spray behaviors after impingement on the curved cylinder wall. In terms of spray dynamics and evolution. numerical results give qualitatively good agreements with experimental data.

• KIEAE Journal
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• 제2권3호
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• pp.55-62
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• 2002

While cognition about an environment pollution becomes important recently, the intense pollution measures about an indoor air environment is required. In the case of building indoor environment, over 80% of modem people is living in building and these days an interest of building interior materials which becomes a reason for indoor environmental pollution in public house, office, is increasing. An experimental measurement method of this study is as follows. (1) American EPA TO-17, ASTMD5116-97, measurement method in VOCs experiment of Japanese closet industrial association (2) 2.4-DNPH cartridge method in HCHO experiment, based on American EPA TO-11 and measurement method of Japanese closet industrial association (3) standard compound is analyzed by using HPLC after solvent extraction process (4) paint and furniture are selected as measurement objects (5) we also made small chamber to grasp an emission characteristic of HCHO and VOCs and to get an environment-amicable forecast model through it, then we developed the model which can forecast emission rate by chamber experiment.

• 한국가구학회지
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• 제15권2호
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• pp.1-17
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• 2004

This paper attempted to review measuring methods of formaldehyde emission from wood-based panel products. Methods included for the discussion were desiccator methods, extraction method, and various chamber methods. First, the procedures and testing conditions of 24-hour desiccator method was critically reviewed, and an improvement of this method was proposed to meet international standards. Two different small chamber methods ($20\ell$ and $1m^3$ chamber methods) were also compared in terms of their advantages and disadvantages. In addition, the regulation levels of formaldehyde emission of wood-based composite panels were compared for different countries. The selection of a reference method of measuring formaldehyde emission of wood panel products should consider the ease of conducting test and cost required. Results should be exchangeable for different methods.

• Journal of Advanced Marine Engineering and Technology
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• 제25권2호
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• pp.395-402
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• 2001

The gasoline engine tends to high performance, fuel economy, small-sized. Therefore, it is necessary to solve the problems on thermal load, abnormal combustion, etc, in the engine, Thine film instantaneous temperature measurement probe was made. And the manufactural method of probe was established. The instantaneous surface temperatures in the constant volume combustion chamber were measured by this probe and the heat flux was obtained by Fourier analysis. The authors measured the wall temperature of combustion chamber and computed the heat flux through the cylinder wall in order to understand the combustion characteristics depending on height of probe. For achieving this goal, the thin film instantaneous temperature probe was developed for analyzing the instantaneous surface wall temperature and unsteady heat flux on the constant volume combustion chamber.

• Journal of Korean Society for Atmospheric Environment
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• 제17권E2호
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• pp.61-70
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• 2001

In recent years there have been growing interests in the potential environmental effects of global climate change. Of specific interests is the role that climate change may play in altering natural volatile organic compound.(NVOC) emissions from trees and the subsequent impact of this perturbation on air quality and ozone formation. A novel vegetation enclosure chamber method was designed and constructed of Tedlar in order to estimate more accurate and precise NVOC emission rates of either small whole plants or the branches of large trees. The enclosure chamber was initially tested in the laboratory and also successfully evaluated in the field. Overall precision for this enclosure was estimated as RSD<10%(n=9). The overall errors associated with the enclosure method in a laboratory system might be relatively small (say<$\pm$15%); however, they might be rather large(say$\pm$40%) in a field-based system. Two consecutive samples were collected on each sampling day from the two pine species during the test period. Slash pine studies showed that the absolute percentage difference between the first and second samples varied from 0.33 to 29%. The percent differences between consecutive emission for loblolly pines varied from 0.74 to 24.2%.

• 한국토양비료학회지
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• 제28권2호
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• pp.183-190
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• 1995

논포장에서 배출되는 메탄가스를 측정하기 위하여 간이폐쇄정태 chamber법을 이용하여 대표적인 시료를 채취할 수 있도록 chamber내 시료채취 높이, 시료채취시 시간간격, 하루중 시료 채취시간을 검토하였다. 1. 대표적인 시료채취를 위한 chamber내 높이는 65cm이었고 chamber 하반부에서 시료가 균일하게 섞이도록 DC fan을 추가로 설치할 필요성이 인정되었다. 2. 시간경과에 따른 chamber내 메탄농도의 변화 및 기온의 변화에서 보면 시료채취를 개시하여 30분이내에 시료를 채취하는 것이 바람직하였다. DC fan으로 chamber내부의 공기가 섞이도록 하는 것은 대표적인 시료를 얻기 위한 것 뿐 아니라 chamber내열평형을 이루어 시료(試料) 채취기간중(採取期間中) 식물(植物)의 생리적(生理的) 활성(活性)에 최소한(最小限)의 변화를 주는 방법으로 판단되었다. 3. 하루중 대표적인 메탄 배출량을 나타내는 오전 9시~12시에 시료를 채취하여 분석하되 부득이한 경우에는 또 하나의 평균적인 배출량을 나타내는 오후 6시~8시의 시료를 채취하여 분석하여도 가능할 것으로 판단되었다. 4. 수도주간(水稻株間)진 토양(土壤)에서 메탄 배출을 측정하는데 사용하는 소형의 chamber는 토양을 교란할 수 있으므로 설치한 후 최소한 6시간이 경과되어야 chamber내 메탄농도가 주위의 메탄 농도로 회복되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.76-81
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• 2012

In-process evaluation equipment for the prominent discrete tone (PDT) emitted by small motors or actuators such as HDD(Hard Disk Driver), ODD(Optical Disk Driver) or linear motors has been developed and estimated on the basis of Prominence Ratio (PR) method in ECMA 74. Correlation of the evaluation equipment was performed in comparison with the method by ECMA 74 in anechoic chamber. Coherent function between two systems was applied in order to compensate traceability of ECMA 74 in anechoic chamber. Usability of the developed system with estimated Gage R&R shall be approved with real samples in the mass production line.

• 대한디지털의료영상학회논문지
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• 제12권1호
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• pp.51-58
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• 2010

Ionization chambers often exhibit a stem effect, caused by interactions of radiation with air near the chamber end, or with dielectric in the chamber stem or cable. In this study measured stem effect correction factor for length of ionization chamber from medical linear accelerator recommend to with the use of stem correction method. For a model of the Farmer-type chamber, were used to calculate the beam quality correction factor. These interactions contribute to the apparent measured exposure. Additionally, it needs to consider ionization chamber use of small volume and stem effect of cable by a large field. Linear accelerator generated photons energy and increased dose repeatedly measured by using stem correction method. Stem effect was dependence of the energy and increases with photon energy conditions improved of beam quality. In conclusion, stem effect correction factor was measured within 0.4% calculated according to the exposures stem length and also supposed to determined below 1% of another stem correction method.