• Transactions of the Korean Society of Mechanical Engineers B
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• v.36 no.4
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• pp.371-376
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• 2012

The experimental test was conducted for a heavy-duty DME bus in JE-05 exhaust gas test mode using a chassis dynamometer, exhaust gas analyzers, and a PM measurement system. The heavy-duty DME bus was not equipped with after-treatment systems such as DOC or DPF. The dynamic behavior, emission characteristics, and fuel economy of the bus were investigated with an 8.0-liter, 6-cylinder conventional diesel engine. The results showed that the dynamic behavior in DME mode was almost the same as in diesel mode. However, there was little difference among the two operation modes for $NO_x$ and CO emissions. THC emissions were lower for DME mode than for diesel mode. Also, the amount of PM emissions was remarkably lower than for the diesel mode because DME contains a greater amount of oxygen than diesel. The data showed that $CO_2$ emissions were almost similar in the two modes but fuel economy (calculated using heating value) was lower for DME mode than for diesel mode.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.7
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• pp.749-755
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• 2011

The performance and emission characteristics of a CNG (compressed natural gas) engine were experimentally investigated under different natural gas compositions. The engine specifications were as follows: 6606 cc, turbo, lean-burn-type; its ignition timing was fixed for the fuel gas with a HHV (higher heating value) of 10454 kcal/$Nm^3$. The experimental results showed that when the HHV of the fuel gas was changed from 10454 kcal/$Nm^3$ to 9811 kcal/$Nm^3$ and 9523 kcal/$Nm^3$, the average power reductions were 3.2 % and 3.4 % (1.5 % and 2.1 %, respectively, with A/F control switched off), respectively, and the average thermal-efficiency reductions were 1.1 % and 1.5 % (1.5 % and 2.1%, respectively, with A/F control switched off), respectively. The emissions of $CO_2$, CO, and $NO_x$ decreased as the HHV of the fuel gas was lowered. On the other hand, the emissions of THC (total hydrocarbon) were not consistent, and the extent of change in their emissions was small.

• Journal of Korean Society of Transportation
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• v.34 no.5
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• pp.377-393
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• 2016

Vehicle emissions have been known as a critical factor to give a negative impact on the public health. In particular, particulate matters(PM) and NOx are highly related with respiratory diseases such as asthma. This study aimed at analyzing spatio-temporal patterns of PM and NOx generated from urban freeway traffic. MOVES, which is a well-known emission analysis tool presented by US Environmental Protection Agency(EPA), was applied to estimate PM and NOx based on traffic volume and speed data obtained from Seoul Outer Ring Expressway during January~June, 2012. K-means clustering analysis was used for categorizing the Level of Vehicle Emissions(LOVE) to support more systematical identification of the significance of emissions. Then, spatio-temporal analyses of estimated emissions were conducted by LOVE. Finally, this study proposed a set of strategies to reduce both PM and NOx to enhance public health based on analysis results.

• Journal of the Korean earth science society
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• v.22 no.6
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• pp.480-490
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• 2001

The soil-air exchange processes of Hg were investigated from the Hari area of Kang Hwa Island during the late March 2001. In the course of our study, we determined the concentration gradients of Hg and combined these gradient data with micrometeorological components to derive its fluxes. Results of our study indicate that the concentration levels of Hg in the study area are notably lower than those typically found in urbanized areas of Korea. However, the computed fluxes were seen to be significantly larger for relatively remote areas, reaching over 200 ng/m$^2$/hr. Comparison of environmental conditions shows that the concentrations of most pollutant species including NO$_X$ and PM were significantly higher during emission, while meteorological conditions were characterized by high temperature and low humidity. Results of correlation analysis also indicate that such pollutants as hydrocarbons, nitrogen oxides, and PM generally exhibit strong positive correlations with Hg-related parameters during emission events, while such relationships were reversed during dry deposition events. The results of our present study suggest the possibility that the concentrations and fluxes of total gaseous Hg observed during deposition events can be influenced by the processes that are also important for the fine, rather than coarse, size fraction of particles.

• Advances in aircraft and spacecraft science
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• v.1 no.3
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• pp.311-330
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• 2014

Environmental impact of aircraft emissions can be addressed in two ways. Air quality impact occurs during landings and takeoffs while in-flight impact during climbs and cruises influences climate change, ozone and UV-radiation. The aim of this paper is to investigate airports related local emissions and fuel consumption (FC). It gives flight path optimization model linked to a dispersion model as well as numerical methods. Operational factors are considered and the cost function integrates objectives taking into account FC and induced pollutant concentrations. We have compared pollutants emitted and their reduction during LTO cycles, optimized flight path and with analysis by Dopelheuer. Pollutants appearing from incomplete and complete combustion processes have been discussed. Because of calculation difficulties, no assessment has been made for the soot, $H_2O$ and $PM_{2.5}$. In addition, because of the low reliability of models quantifying pollutant emissions of the APU, an empirical evaluation has been done. This is based on Benson's fuel flow method. A new model, giving FC and predicting the in-flight emissions, has been developed. It fits with the Boeing FC model. We confirm that FC can be reduced by 3% for takeoffs and 27% for landings. This contributes to analyze the intelligent fuel gauge computing the in-flight fuel flow. Further research is needed to define the role of $NO_x$ which is emitted during the combustion process derived from the ambient air, not the fuel. Models are needed for analyzing the effects of fleet composition and engine combinations on emission factors and fuel flow assessment.

• Particle and aerosol research
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• v.6 no.2
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• pp.51-59
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• 2010

ZnO quantum dots embedded in a silica matrix without agglomeration were synthesized from $TEOS:Zn(NO_3)_2$ solutions in one-step process by aerosol-gel method. It was successfully demonstrated that the size of ZnO Q-dots could be controlled from 2 to 7 mm verified by a high resolution transmission electron microscope observation. The line scanning energy dispersive X-ray spectroscopy(EDS) revealed that the Q-dots existed preferentially inside SiO2 sphere when Zn/Si < 0.5. However, the Q-dots distributed homogeneously all over the sphere when Zn/Si > 1.0. Blue-shifted UV/Vis absorption peak observation confirmed the quantum size effect on the optical properties. The photoluminescence(PL) emission peaks of the powders at room temperature were consistent with previous reports in the following aspects: 1) PL characteristics are dominated by two peaks of deep-level defect-related emissions at 2.4 - 2.8 eV, 2) the first defect-related peak at 2.4 eV was blue shifted due to the quantum size effect with decreasing the concentration of $Zn(NO_3)_2$(decreasing the size of ZnO q dots). More interestingly, the existence of surface-exposed ZnO q dots affects greatly the second defect PL peak at 2.8 eV.

• Journal of Korean Neurosurgical Society
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• v.56 no.5
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• pp.431-435
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• 2014

A fifty-year-old female non-smoker with no other specific medical history visited our institute. She complained of axial back pain with no other neurological deficit. Chest X-ray, chest computed tomography (CT) scan, CT-guided needle aspiration biopsy, whole-body positron emission tomography, spine CT and spine magnetic resonance image findings suggested NSCLC with epidermal growth factor receptor (EGFR) mutation, multiple brain metastases, and two isolated metastases to the T3 and L3 vertebral bodies. She underwent chemotherapy with gefitinib ($Iressa^{TM}$) for NSCLC and gamma knife surgery for multiple brain metastases. We performed a two-staged, total en bloc spondylectomy of the T3 and L3 vertebral bodies based on several good prognostic characteristics, such as the lack of metastases to the appendicular bone, good preoperative performance status, and being an excellent responder (Asian, never-smoker and adenocarcinoma histology) to EGFR inhibitors. Improved axial back pain after the surgery enabled her to walk with the aid of a thoracolumbosacral orthosis brace on the third postoperative day. Her Karnofsky performance status score (KPS) was 90 at the time of discharge and has been maintained to date 3 years after surgery. In selected NSCLC patients with good prognostic characteristics, we suggest that locally curative treatment such as total en bloc spondylectomy or radiosurgery should be emphasized to achieve longer term survival for the selected cases.

• Korean Journal of Materials Research
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• v.25 no.2
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• pp.95-99
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• 2015

$NiAl_2O_4$ nanoparticle was synthesized by a reverse micelle processing for inorganic pigment. $Ni(NO_3)_2{\cdot}6H_2O$ and $Al(NO_3)_3{\cdot}9H_2O$ were used for the precursor in order to synthesize $NiAl_2O_4$ nanoparticles. The aqueous solution, which consisted of a mixing molar ratio of Ni/Al, was 1:2 and heat treated at $800{\sim}1100^{\circ}C$ for 2h. The average size and distribution of synthesized $NiAl_2O_4$ powders are in the range of 10-20 nm and narrow, respectively. The average size of the synthesized $NiAl_2O_4$ powders increased with an increasing water-to-surfactant molar ratio and heating temperature. The crystallinity of synthesized $NiAl_2O_4$ powder increased with an increasing heating temperature. The synthesized $NiAl_2O_4$ powders were characterized by X-ray diffraction analysis(XRD), a field emission scanning electron microscopy(FE-SEM), and a color spectrophotometer. The properties of synthesized powders were affected as a function such as a molar ratio and heating temperature. Results indicate that synthesis using a reverse miclle processing is a favorable process to obtain $NiAl_2O_4$ spinels at low temperatures. The procedure performed suggests that this new synthesis route for producing these oxides has the advantage of being fast and simple. Colorimetric coordinates indicate that the pigments obtained exhibit blue colors.

• Korean Journal of Materials Research
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• v.21 no.8
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• pp.468-475
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• 2011

[ $LaMeO_3$ ](Me = Cr, Co) powders were prepared using the polymeric precursor method. The effects of the chelating agent and the polymeric additive on the synthesis of the $LaMeO_3$ perovskite were studied. The samples were synthesized using ethylene glycol (EG) as the solvent, acetyl acetone (AcAc) as the chelating agent, and polyvinylpyrrolidone (PVP) as the polymer additive. The thermal decomposition behavior of the precursor powder was characterized using a thermal analysis (TG-DTA). The crystallization and particle sizes of the $LaMeO_3$ powders were investigated via powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and particle size analyzer, respectively. The as-prepared precursor primarily has $LaMeO_3$ at the optimum condition, i.e. for a molar ratio of both metal-source (a : a) : EG (80a : 80a) : AcAc (8a) inclusive of 1 wt% PVP. When the as-prepared precursor was calcined at $700^{\circ}C$, only a single phase was observed to correspond with the orthorhombic structure of $LaCrO_3$ and the rhombohedral structure of $LaCoO_3$. A solid-electrolyte impedance-metric sensor device composed of $Li_{1.5}Al_{0.5}Ti_{1.5}(PO_4)_3$ as a transducer and $LaMeO_3$ as a receptor has been systematically investigated for the detection of NOx in the range of 20 to 250 ppm at $400^{\circ}C$. The sensor responses were able to divide the component between resistance and capacitance. The impedance-metric sensor for the NO showed higher sensitivity compared with $NO_2$. The responses of the impedance-metric sensor device showed dependence on each value of the NOx concentration.

• Restorative Dentistry and Endodontics
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• v.38 no.3
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• pp.134-140
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• 2013

Objectives: There has been a growing interest in glass ceramic systems with good esthetics, high fracture resistance and bonding durability, and simplified fabrication techniques using CAD/CAM. The aim of this study is to compare flexural strength before and after heat treatment of two lithium disilicate CAD/CAM blocks, IPS e.max CAD (Ivoclar Vivadent) and Rosetta SM (Hass), and to observe their crystalline structures. Materials and Methods: Biaxial flexural strength was tested according to ISO 6872 with 20 disc form specimens sliced from each block before and after heat treatment. Also, the crystalline structures were observed using field-emission scanning microscopy (FE-SEM, Hitachi) and x-ray diffraction (XRD, Rigaku) analysis. The mean values of the biaxial flexural strength were analyzed by the Mann-Whitney U test at a significance level of p = 0.05. Results: There were no statistically significant differences in flexural strength between IPS e.max CAD and Rosetta SM either before heat treatment or after heat treatment. For both ceramics, the initial flexural strength greatly increased after heat treatment, with significant differences (p < 0.05). The FE-SEM images presented similar patterns of crystalline structure in the two ceramics. In the XRD analysis, they also had similar patterns, presenting high peak positions corresponding to the standard lithium metasilicate and lithium disilicate at each stage of heat treatment. Conclusions: IPS e.max CAD and Rosetta SM showed no significant differences in flexural strength. They had a similar crystalline pattern and molecular composition.