• Journal of Mechanical Science and Technology
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• 제16권2호
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• pp.219-226
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• 2002

Natural gas is considered to be a promising alternative fuel for passenger cars, truck transportation and stationary engines providing positive effects both on the environment and energy security. However, since the composition of natural gas fuel varies with location, climate and other factors, it is anticipated that such changes in fuel properties will affect emission characteristics and performance of CNG (Compressed Natural Gas) engines. The purpose of the present study is to investigate the effects of the difference in gas composition on the engine performance and emission characteristics. The results show that THC (Total Hydrocarbon) decreases with increasing Wl (Wobbe Index) and MCP (Maximum Combustion Potential). On the other hand, it is observed that NOx slightly increases as Wl and MCP increase. The TLHV (Total Lower Heating Value of Intake) is proposed in this study as a potential index for compatibility of gas fuels in a CNG engine. There is a variation in power up to 20% depending on the composition of gas when the A/F ratio and spark timing are flexed for a specific gas fuel.

• Nuclear Engineering and Technology
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• 제55권12호
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• pp.4591-4596
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• 2023

Single-photon emission computed tomography SPECT image reconstruction methods have a significant influence on image quality, with filtered back projection (FBP) and ordered subset expectation maximization (OSEM) being the most commonly used methods. In this study, we proposed newly-designed adaptive non-blind deconvolution with a structural similarity (SSIM) index that can take advantage of the FBP and OSEM image reconstruction methods. After acquiring brain SPECT images, the proposed image was obtained using an algorithm that applied the SSIM metric, defined by predicting the distribution and amount of blurring. As a result of the contrast to noise ratio (CNR) and coefficient of variation evaluation (COV), the resulting image of the proposed algorithm showed a similar trend in spatial resolution to that of FBP, while obtaining values similar to those of OSEM. In addition, we confirmed that the CNR and COV values of the proposed algorithm improved by approximately 1.69 and 1.59 times, respectively, compared with those of the algorithm involving an inappropriate deblurring process. To summarize, we proposed a new type of algorithm that combines the advantages of SPECT image reconstruction techniques and is expected to be applicable in various fields.

• 천문학회지
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• 제27권1호
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• pp.81-102
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• 1994

We have decomposed the 11-cm radio continuum emission of the W51 complex into thermal and non-thermal components. The distribution of the thermal emission has been determined by analyzing HI, CO, and IRAS $60-{\mu}m$ data. We have found a good correlation between the 11-cm thermal continuum and the 60- 11m emissions, which is used to obtain the thermal and non-thermal 11-cm continuum maps of the W51 complex. Most of the thermal continuum is emanating from the compact H II regions and their low-density ionized envelopes in W51A and W51B. All the H II regions, except G49.1-0.4 in W51B, have associated molecular clumps. The thermal radio continuum fluxes of the compact H II regions are proportional to the CO fluxes of molecular clumps. This is consistent with the previous results that the total mass of stars in an H II region is proportional to the mass of the associated molecular clump. According to our result, there are three non-thermal continuum sources in W51: G49.4-0.4 in W51A, a weak source close to G49.2-0.3 in W51B, and the shell source W51C. The non-thermal flux of G49.5-0.4 at 11-cm is $\~28 Jy$, which is $\~25\%$ of its total 11-cm flux. The radio continuum spectrum between 0.15 and 300 GHz also suggests an excess emission over thermal free-free emission. We show that the excess emission can be described as a non-thermal emission with a spectral index ${\alpha}{\simeq}-1.0 (S_v{\propto}V^a)$ attenuated by thermal free-free absorptions at low-frequencies. The non-thermal source close to G49.2-0.3 is weak $(\~9 Jy)$. The nature of the source is not known and the reality of the non-thermal emission needs to be confirmed. The non~thermal shell source W51C has a 11-cm flux of $\~130Jy$ and a spectral index ${\alpha}{\simeq}-0.26$.

• 천문학회지
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• 제55권2호
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• pp.59-66
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• 2022

Stellar magnetic activity is important for formulating the evolution of the star. To represent the stellar magnetic activity, the S index is defined using the Ca II H+K flux measure from the Mount Wilson Observatory. Mg II lines are generated in a manner similar to the formation of Ca II lines, which are more sensitive to weak chromospheric activity. Mg II flux data are available from the International Ultraviolet Explorer (IUE). Thus, the main purpose of this study was to analyze the magnetic activity of stars. We used 343 high-resolution IUE spectra of 14 main-sequence G stars to obtain the Mg II continuum surface flux and Mg II line-core flux around 2,800 Å. We calculated S index using the IUE spectra and compared it with the conventional Mount Wilson S index. We found a color (B - V ) dependent association between the S index and the Mg II emission line-core flux. Furthermore, we attempted to obtain the magnetic activity cycles of these stars based on the new S index. Unfortunately, this was not successful because the IUE observation interval of approximately 17 years is too short to estimate the magnetic activity cycles of G-type stars, whose cycles may be longer than the 11 year mean activity cycle of the sun.

• 한국연소학회지
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• 제17권3호
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• pp.1-8
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• 2012

The CO emission characteristics of interacting hydrogen and methane partially premixed flames were numerically investigated. A counterflow geometry was introduced to establish interacting two partially premixed flames. An one-dimensional OPPDIF code was used to simulate the interacting flames. The GRI-v3.0 was used to calculate the chemical reactions. Emission index for CO(EICO) was evaluated to quantify the CO emitted from the interacting flames. The global strain rate and equivalence ratios for each flame(${\Phi}_{CH_4}$ and ${\Phi}_{H_2}$) were used as parameters to control the extent of interaction between two partially premixed flames. When ${\Phi}_{CH_4}$ was kept to stoichiometric condition and ${\Phi}_{H_2}$ was at rich condition, unburned H2 species of hydrogen flame was transported to the methane flame and affected reactions related with CO formation. When ${\Phi}_{CH_4}$ increased from a stoichiometry to rich condition while ${\Phi}_{H_2}$ was kept to stoichiometric condition, EICO increased initially, had a peak value at ${\Phi}_{CH_4}=1.5$ and decreased gradually. This could be elucidated with an analysis for the elementary reactions related with CO formation.

• KIEAE Journal
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• 제7권1호
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• pp.57-64
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• 2007

This study aims to propose appropriate evaluating method of noise emission from water supply and drain installations in apartment bathroom. The measurement procedure of water installations noise in apartment bathroom were established, so it is necessary to provide the evaluating method and criteria to improve the sound insulation performance of the apartment and to reduce the apartment dweller's unsatisfaction with the noise. Thus, this study reviewed the standards and evaluating methods about the water supply and drain installations noise of many other country. After measuring the noise emission from the installations in many apartment bathroom, The noise were evaluated dB(A), N, NC index, To induce the appropriate method, the coefficient of the correlation among the evaluated numbers were analyzed. As a result, the dB(A) method is most easy to evaluating and very high correlated with N and N index, So the dB(A) method is suitable to be adopted KS evaluating procedure of noise emission from water installations in apartment bathroom.

• 자원ㆍ환경경제연구
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• 제20권2호
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• pp.229-254
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• 2011

본 논문은 LMDI(Log Mean Divisia Index) 방법론을 이용하여 국내 제조업의 온실가스 배출에 대한 요인분해분석을 하였다. 국내 제조업의 온실가스 배출에 대한 요인분해는 크게 생산효과, 구조효과, 집약도효과, 에너지믹스효과, 배출계수효과 등 다섯 가지 요인으로 분해하였다. 1991년~2007년까지 국내 제조업의 온실가스 배출변화 요인을 분석한 결과를 보면 국내 제조업의 온실가스 배출은 대부분 생산효과에 의해서 증가하였다. 구조효과와 집약도는 온실가스 배출을 줄이는 역할을 하였으며, 구조효과보다는 집약도효과가 더 많이 온실가스 배출을 감소시키는 방향으로 작용하였다. 그리고 에너지믹스효과와 배출계수효과는 다른 효과들에 비해서 그 비중이 작지만 온실가스 배출 증감에 영향을 미치고 있다. 에너지믹스효과는 온실가스 배출 증가 요인으로 배출계수효과는 감소요인으로 작용하였다. 한편 시계열로 에너지 소비를 요인분해 해 본 결과 1998년 IMF 체제를 전후로 온실가스 패턴에 변화가 일어났다. IMF 체제 이후로 구조효과와 집약도효과에 의한 온실가스 감축이 IMF 체제 이전보다 더욱 두드러진 것이 특징이다. 2001년 이후 진행된 신고유가 시대를 맞이해서는 구조효과와 집약도효과가 더욱 촉진되었다.

• 자원ㆍ환경경제연구
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• 제19권2호
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• pp.243-282
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• 2010

본 연구는 1991년~2007년간 우리나라 전력산업의 탄소배출에 미치는 요인들과 영향의 정도를 전력 수요측면과 공급측면으로 나누어 요인분해분석을 수행하였다. 전력수요측면에서는 전력사용의 효율성 향상이 배출 감소에 주된 영향을 미치는 반면, 전력을 소비하는 산업의 구조 변화는 오히려 배출을 증가시키는데 기여했음을 확인하였다. 공급측면에서는 탄소배출에 미치는 주요 요인으로 연료혼합, 화력발전효율, 발전구조의 변화 등이 있었으며 분석 결과 전력수요의 증가와 화력발전의 구조 변화가 탄소배출을 증가시키는 주요한 요인으로 작용한 반면 연료효율성은 향상되어 배출을 감소시키는 역할을 한 것으로 나타났다. 이로써 전력산업의 온실가스 감축을 위해 수요차원에서는 전력사용의 효율성을 향상시키고 공급차원에서는 화력발전을 대체하면서 발전 및 배출 효율성을 향상시킬 수 있는 정책이 마련되어야 한다는 것을 알 수 있었다.

• Applied Science and Convergence Technology
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• 제25권1호
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• pp.1-6
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• 2016

Quantum dots (QDs) are considered as excellent color conversion and self-emitting materials for display and lighting applications. In this article, various technologies which can be used to realize white light emission with QDs are discussed. QDs have good color purity with a narrow emission spectrum and tunable optical properties with size control capabilities. For white light emission with a color-conversion approach, QDs are combined with blue-emitting inorganic and organic light-emitting diodes (LED) to generate white emission with high energy conversion efficiency and a high color rendering index for various display and lighting applications. Various device structures for self-emitting white QD light-emitting diodes (QD-LED) are also reviewed. Various stacking and patterning technologies are discussed in relation to QD-LED devices.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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• pp.247-250
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• 2001

We studied optical properties of SiON thin-film in the applications of optical waveguide. SiON thin-film was grown in $300^{\circ}C$ by PECVD(plasma enhanced chemical vapor deposition) system. The change of SiON thin-film composition and refractive Index was studied as a function of varying $NH_3$ gas flow rate. As $NH_3$ gas flow rate was increased, Quantity of N and refractive index were increased at the same time. By the results, we could form the SiON thin-film to use of a waveguide with refractive index of 1.6. We analyzed the conditions of the thin-film with FTIR(fourier transform infrared) and OES (optical emission spectroscopy). N-H bonding($3390cm^{-1}$ ) can be removed by thermal annealing. And we could observe the SiH bonding state and quantity by OES analysis in $SiH_4$