• Proceedings of the Korea Air Pollution Research Association Conference
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• 2000.11a
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• pp.136-138
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• 2000

The vehicle emissions of primary air pollutants are described by the emission factor (EF), defined as the emitted mass (g) of a compound per distance (km) and vehicle. The EF can be determined by exhaust measurements from single vehicles in dynamometric tests. However, the EF of a large number of vehicles has to be measured to obtain the representative results for actual road traffic emissions. Road traffic emissions can also be determined by exhaust measurements of driving vehicles or in tunnel measurements. (omitted)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2001.11a
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• pp.257-258
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• 2001

대기중 PM의 물리ㆍ화학적 특성은 발생 원의 종류에 따라 큰 차이가 있으며, 발생원에서 직접 배출된 1차 생성입자(Primary particles)와 가스상 물질이 물리ㆍ화학적 반응에 의하여 성장되거나 생성ㆍ변환되어 1차 생성입자와는 전혀 다른 2차 생성입자(Secondary particles)로 황산염, 질산염 및 유기물질 등이 있다. (중략)

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2008.04a
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• pp.706-707
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• 2008

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.15 no.10
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• pp.795-801
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• 2003

The primary object of this study is to obtain a basic knowledge of heat transfer enhancement mechanism as affected by temperature driven Marangoni convection. Experiments is achieved to visualize the enhanced heat transfer phenomena by the effect of Marangoni convection through the laser holographic interferometry. Also Nusselt Number is introduced for the relation of Marangoni Number.

• 한국연소학회:학술대회논문집
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• 2015.12a
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• pp.177-180
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• 2015

The chemical aspects of primary reference fuel (PRF)/air mixture under RCCI conditions are investigated to provide fundamental insights into the ignition characteristics of RCCI combustion. Chemical explosive mode analysis (CEMA) is adopted to understand the ignition process of the lean PRF/air mixture by identifying controlling species and elementary reactions at different locations and times.

• Journal of radiological science and technology
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• v.40 no.1
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• pp.71-78
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• 2017

Scattered radiation is inherent phenomenon of x-ray, which occurs to the subject (or patient). Therefore it cannot be avoidable but also interacts as serious noise factor because the only meaningful information on x-ray radiography is primary x-ray photons. The purpose of this study was to quantify scattered radiation for various shooting parameters and to verify the effect of anti-scatter grid. We employed beam stopper method to characterize scatter to primary ratio. To evaluate effect on the projection images calculated contrast to noise ratio of given shooting parameters. From the experiments, we identified the scattered radiation increases in thicker patient and smaller air gap. Moreover, scattered radiation degraded contrast to noise ratio of the projection images. We find out that the anti-scatter grid rejected scattered radiation effectively, however there were not fewer than 100% of scatter to primary ratio in some shooting parameters. The results demonstrate that the scattered radiation was serious problem of medical x-ray system, we confirmed that the scattered radiation was not considerable factor of dig ital radiog raphy.

• Smart Structures and Systems
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• v.25 no.1
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• pp.65-80
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• 2020

In order to protect a structure over its full life cycle, a novel tuned mass damper (TMD), the so-called semi-active eddy current pendulum tuned mass damper (SAEC-PTMD), which can retune its frequency and damping ratio in real-time, is proposed in this study. The structural instantaneous frequency is identified through a Hilbert-Huang transformation (HHT), and the SAEC-PTMD pendulum is adjusted through an HHT-based control algorithm. The eddy current damping parameters are discussed, and the relationship between effective damping coefficients and air gaps is fitted through a polynomial function. The semi-active eddy current damping can be adjusted in real-time by adjusting the air gap based on the linear-quadratic-Gaussian (LQG)-based control algorithm. To verify the vibration control effect of the SAEC-PTMD, an idealized linear primary structure equipped with an SAEC-PTMD excited by harmonic excitations and near-fault pulse-like earthquake excitations is proposed as one of the two case studies. Under strong earthquakes, structures may go into the nonlinear state, while the Bouc-Wen model has a wild application in simulating the hysteretic characteristic. Therefore, in the other case study, a nonlinear primary structure based on the Bouc-Wen model is proposed. An optimal passive TMD is used for comparison and the detuning effect, which results from the cumulative damage to primary structures, is considered. The maximum and root-mean-square (RMS) values of structural acceleration and displacement time history response, structural acceleration, and displacement response spectra are used as evaluation indices. Power analyses for one earthquake excitation are presented as an example to further study the energy dissipation effect of an SAECPTMD. The results indicate that an SAEC-PTMD performs better than an optimized passive TMD, both before and after damage occurs to the primary structure.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.23 no.3
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• pp.222-228
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• 2013

Objectives: The indoor air quality of newly-built (NC) and remodeled (RC) school classrooms was assessed. The primary aim was to show correlations between volatile organic compounds (VOCs) and formaldehyde (HCHO) pollutant levels. Methods: This study investigated the indoor air concentrations of VOCs and HCHO at 26 sites of newly built and 68 sites of remodeled classrooms located in South Gyeongsang Province between 2010 and 2012. VOCs in the indoor air were determined by adsorbent tube (Tenax TA) and automatic thermal desorption coupled with GC-MS analysis. Target analytes were five VOCs: benzene, toluene, ethylbenzene, xylene, and styrene. HCHO was collected with a 2,4-DNPH cartridge and analyzed by HPLC. Conclusions: This study estimated that indoor VOCs and HCHO concentrations in the classrooms were mainly affected by interior building materials and classroom equipment. For proper indoor air quality in schools, classroom air should be improved through reduction of hazardous materials by adequate ventilation, selecting environmental friendly materials, etc.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.468-472
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• 2005

In this paper, the static and dynamic stiffness of the air bearing stage for micro-micro machine tool are examined experimentally. For stiffness and precision concerns, air bearing stages are adapted for 3-axis micro-milling machine which is size of $200x200\;mm^2$. The air bearings in the stage are preloaded by permanent magnets to achieve desired bearing clearance and stiffness for vertical direction. As the stiffness of the air bearing is primary interests, static stiffness test were performed on XY stage in Z direction and Z column in Y direction. Dynamic test were performed on XY stage and Z column, respectively. Both static and dynamic tests were performed in different air pressure conditions. The vertical stiffness of XY stage is about 9 N/ pm where Y stiffness of Z column is much smaller as $1\;N/{\mu}m$ because of the large moment generated by Y force on the column.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.7
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• pp.409-416
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• 2009

On 21st century, global warming is the most serious environmental problem threatening the existence of lives on the earth. One of the serious reasons of this nature phenomena was due to the greenhouse effect by carbon dioxide mainly produced with the combustion process of hydro-carbon fuel. and it is mostly produced. In the high oil prices age, intensification of energy efficiency promotion in the building sector is required. Windows are dominating large percentage whole building loads, and are regarding as the primary target of energy efficiency. The purpose of this research is on the obtaining of the renewable energy source in the skyscrape buildings in the metropolitan area. The air movement is happens due to the atmospheric pressure differences in the air. Due to this simple physical theory, it is easily expected to obtain the useful renewable nature energy through the high -raised vertical air stack installed in a tall building. However, there is one problem that should be resolved which is called air-hole effect in the sky -scrape buildings.