• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.5
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• pp.116-125
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• 2014

Pyrolysis oil (PO), derived from biomass through fast pyrolysis process have the potential to displace significant amounts of petroleum fuels. The PO derived from wood has been regarded as an alternative fuel to be used in diesel engines. However, the use of PO in a diesel engine is very limited due to its poor properties like low energy density, low cetane number, high acidity and high viscosity of PO. Therefore, one of the easiest way to adopt PO to diesel engine without modifications is blended with other fuels that have high centane number. However, PO that has high amount of polar chemicals is immiscible with non polar hydrocarbons of diesel or biodiesel. Thus, to stabilize a homogeneous phase of diesel/biodiesel-PO blends, a proper surfactant should be used. Nevertheless, PO which was produced from different biomass type have varied characteristics and this complicates the selection of a suitable additive for a specific PO-diesel emulsion. In this regard, a more simple approach such as the use of a co-solvent like ethanol or butanol to induce a more stable phase of the PO-diesel mixture could be a promising alternative. In this study, a diesel engine operated with diesel/biodiesel-PO-butanol blends was experimentally investigated. Performance and gaseous & particle emission characteristics of a diesel engine were examined under the engine loads of IMEP 0.2 ~ 0.8MPa.

• Journal of Conservation Science
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• v.36 no.2
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• pp.103-111
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• 2020

To compare the cleaning effect of solvents such as water and ethanol used to clean lacquer relics, the components extracted with various solvents were analyzed. A freshly dried lacquer sample and a lacquer sample exposed to ultraviolet radiation for 24 days were treated with water, ethanol, acetone, and hexane, and the dissolved material was detected by pyrolysis-gas chromatography-mass spectrometry. The amount extracted was significantly higher in acetone and ethanol than in hexane, a nonpolar solvent. Water, a highly polar solvent, was relatively efficient for extracting low-molecular-weight materials. After experiencing 24 days of ultraviolet radiation, the lacquer exhibited a significant increase of extracted materials compared with the nonexposed one. This may be due to the degradation of the urushiol chain in the form of polymers, resulting in the formation of low-molecular-weight polar substances, including dicarboxylic acids. In addition to the deterioration status of lacquer relics, such solvent extraction properties will be a crucial consideration in selecting the appropriate cleaning solvent.

• Macromolecular Research
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• v.14 no.2
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• pp.179-186
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• 2006

In the present work, low density polyethylene (LDPE)/aliphatic polyester (APES)/organoclay ternary nanocomposites were prepared. In particular, the effect of a compatibilizer, polyethylene-graft-maleic anhydride (PE-g-MAH), on the morphology and properties of the ternary nanocomposites was investigated. LDPE/APES/organoclay nanocomposites were prepared through melt intercalation method using two different kinds of organoclay. The dispersibility of silicate clays in the nanocomposites was investigated by X-ray diffraction and atomic force microscopy. The ternary nanocomposites showed higher tensile properties than the LDPE/APES blend did. The dispersibility and properties of nanocomposites containing Cloisite 30B were better than those of the nanocomposites containing Cloisite 20A. Unlike Cloisite 20A, hydroxyl groups in the intercalants in Cloisite 30B interlayer underwent a certain polar interaction with the carboxyl group of APES, favoring the intercalation of APES chains and the formation of LDPE/APES/Closite 30B nanocomposites. However, the introduction of the polar hydroxyl groups also enhanced the interaction with the silicate surface at the same time, thereby rendering somewhat difficult the replacement of the surface contacts by LDPE chains, and impeding the extensive intercalation and further exfoliation of Cloisite 30B in the LDPE/APES matrix. The compatibilizer enhanced the intercalation of the polymer chain inside the clay gallery and thus improved the mechanical properties of the ternary nanocomposites. Rheological measurements of the nanocomposites via frequency sweep experiment indicated a certain interaction between the clay platelet and the polymer molecules in the melted state.

• Ocean and Polar Research
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• v.29 no.1
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• pp.33-42
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• 2007

To obtain the overall distribution patterns and characteristics of the East Sea Intermediate Water (ESIW), the historical data obtained by the Japan Maizuru Marine Observatory (MMO) and the Korea Ocean Research and Development Institute (KORDI) were analyzed. To obtain water characteristics of the ESIW on isopycnal surfaces, temperature, salinity and dissolved oxygen were interpolated at every 0.01 interval of potential density. And then the interpolated values were averaged at the same potential density. This potential density average method preserved the salinity minimum layer more clearly compared to the depth average method. The potential density(${\sigma}_{\theta}$) range of the ESIW was $26.9{\sim}27.3$. The representative potential density of the ESIW was found to be 27.2, because the characteristics of the ESIW was clear at this density. From the horizontal distributions of physical properties on the isopycnal surface of $27.2{\sigma}_{\theta}$ it is suggested that the low salinity ESIW circulates anticlockwise over the whole basin with the high salinity intermediate water. The low salinity intermediate water extended from the northwestern part to the east along the sub-polar front and to the Ulleung Basin along the east coast of Korea.

• Journal of Astronomy and Space Sciences
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• v.34 no.4
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• pp.245-250
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• 2017

As a part of collaborative efforts to understand ionospheric irregularities, the Korea ionospheric scintillation sites (KISS) network has been built based on global positioning system (GPS) receivers with sampling rates higher than 1 Hz. We produce the rate of TEC index (ROTI) to represent GPS TEC fluctuations related to ionospheric irregularities. In the KISS network, two ground-based GPS sites at Kiruna (marker: KIRN; geographic: $67.9^{\circ}$ N, $21.4^{\circ}$ E; geomagnetic: $65.2^{\circ}$ N) and Chuuk (marker: CHUK; geographic: $7.5^{\circ}$ N, $151.9^{\circ}$ E; geomagnetic: $0.4^{\circ}$ N) were selected to evaluate the ROTI value for ionospheric irregularities during the occurrence of the 2015 St. Patrick's Day storm. The KIRN ROTI values in the aurora region appear to be generally much higher than the CHUK ROTI values in the EIA region. The CHUK ROTI values increased to ~0.5 TECU/min around UT=13:00 (LT=23:00) on March 16 in the quiet geomagnetic condition. On March 17, 2015, CHUK ROTI values more than 1.0 TECU/min were measured between UT=9:00 and 12:00 (LT=19:00 and 22:00) during the first main phase of the St. Patrick's Day storm. This may be due to ionospheric irregularities by increased pre-reversal enhancement (PRE) after sunset during the geomagnetic storm. Post-midnight, the CHUK ROTI showed two peaks of ~0.5 TECU/min and ~0.3 TECU/min near UT=15:00 (LT=01:00) and UT=18:00 (LT=04:00) at the second main phase. The KIRN site showed significant peaks of ROTI around geomagnetic latitude=$63.3^{\circ}$ N and MLT=15:40 on the same day. These can be explained by enhanced ionospheric irregularities in the auroral oval at the maximum of AE index

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.5
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• pp.870-878
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• 2008

The level of security of most sensor nodes that comprise the sensor networks is low, but because of the low computing power and small storage capacity, it is even very difficult to apply a security algorithm efficiently to the sensor nodes. Therefore, preventing the join of an illegal node to a sensor network is impossible, and the transmitting information is easily exposed and overheard when the transmitting algorithm of the sensor node is hewn. In this paper, we propose a group key management scheme for the sensor network using polar coordinates, so that the sensor nodes can deliver information securely inside a cluster and any illegal node is prevented from joining to the cluster where a sensor network is composed of many clusters. In the proposed scheme, all of the sensor nodes in a cluster set up the authentication keys based on the pivot value provided by the CH. The intensive simulations show that the proposed scheme outperforms the pair-wise scheme in terms of the secure key management and the prevention of the illegal nodes joining to the network.

• Journal of the Korean Society of Safety
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• v.39 no.1
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• pp.9-15
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• 2024

Hydrogen-based electricity and transportation systems are widely recognized as sustainable power sources. However, the low ignition energy of hydrogen, only 1/10th that of conventional fossil fuels, poses a safety concern involving the risk of ignition due to electrostatic discharge from facility workers. Therefore, anti-static systems are imperative for hydrogen-based electricity facilities. To address this, we propose a reliable conductive rubber mat (CRM) to ensure the safety of these facilities. Unlike conventional anti-static floors that utilize conductive paint (CP), the CRM features a uniform distribution of conductive components in chemically and mechanically stable rubber. As a result, the CRM is unyielding to polar solvents (such as ethanol and hydrosulfuric acid) and non-polar solvents (like mineral oil) without increasing its resistance. Moreover, the CRM can withstand mechanical stress. Consequently, the human-body voltage of workers on the CRM would be sufficiently low enough to protect them from hydrogen explosions, thereby enhancing overall safety.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.5 no.2
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• pp.200-211
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• 1995

This study was designed to evaluate the effects of temperature and humidity on the sampling efficiency of mixed organic vapors of l,2-DCE, benzene, and MIBK by 3 different types of diffusion monitors. Independent variables used for the study were temperatures ($25^{\circ}C$, $35^{\circ}C$), humidities (30%, 80%), and vapor concentrations (low, medium, and high). In addition, vapor concentrations measured by the traditional charcoal tube method were used as reference values and were compared with those of by diffusion monitors. The results were as follows: 1. The desorption efficiencies(DE) of 1,2-DCE and benzene from charcoal tubes and from diffusion monitors ranged from 98% to 105%. In contrast, the DEs of MIBK from charcoal tubes and diffusion monitors except DM1 ranged from 71% to 85%. The DE of MIBK from DM1 was 98%. 2. No statistically significant differences of 1,2-DCE concentrations and the sampling efficiencies regardless of temperatures and humidities studied between charcoal tube and 3 diffusion monitors were found. 3. At 80% humidity, increasing frequencies of 1,2-DCE breakthrough at higher temperature and higher vapor concentration measured by charcoal tubes were observed. 4. No statistically significant difference of benzene concentrations were found between charcoal tube and diffusion monitors except DM3. The sampling efficiencies of DM3 were statistically significantly lower at all experimental conditions except the $35^{\circ}C$ and 30% humidity condition. 5. No statistically significant difference of MIBK concentrations were found between charcoal tube and diffusion monitors except DM3. The sampling efficiencies of DM3 were statistically significantly higher at higher humidity conditions regardless of temperature. Although statistically not significant, sampling efficiency of MIBK showed positive correlation with humidity while negative correlation with concentration was observed. 6. For sampling 1,2-DCE and benzene, no significant variations of concentrations among three diffusion monitors regardless of temperature and humidity conditions were found. For MIBK sampling, however, wide variations with increasing humidity among diffusion monitors were obtained. In conclusion, this study suggests that diffusion monitors will be a reasonables substitute for the traditional charcoal tubes for sampling non-polar organic vapors at temperature and humidity conditions studied. For polar organic vapors, use of an alternative desorption solution other than CS2 is recommended because of its low desorption efficiency. In addition, since variable among diffusion monitors for polar organic vapors particularly at higher humidity conditions were observed, further study is recommended of the effects of humidity on the performance of diffusion monitors.

• Journal of Astronomy and Space Sciences
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• v.19 no.1
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• pp.75-88
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• 2002

The climatological characteristics of the polar ionosphere is examined in terms of the ionospheric conductance and electric field. For this purpose, 109 days of measurements from the Sondrestrom incoherent scatter radar are utilized. By combining these two quantities, it is possible to deduce the overhead ionospheric current distributions. The ionospheric current density thus obtained is compared with the corresponding ground magnetic disturbance. Also examined is the effect of the field-aligned current on the ground magnetic disturbance, particularly on the D component Several interesting climatological characteristics about the ionosphere over the Sonderstrom are apparent from this study. (1) The conductance distribution is mainly due to solar EUV radiation during day-time On the other hand, the conductance distribution during the night-time is very low. (2) The conductance distribution one. the polar cap region during the day-time is controlled mostly by the solar EUV radiation, while it is extremely low during night-time wish the Hall and Pedersen conductances being 1.6 and 1.2 siemen, respectively (3) The region of the maximum N-S electric field tend to locate in the dayside sector. The E-W component of the electric field is stronger than that over Chatanika (4) The E-W auroal inospheric current (J/sub E/) is more important in the sunlit hemisphere than the night hemisphere. And a strong southward current is noted in the prenoon sector (5) There is a significant correlation between the overhead ionospheric current and the simultaneously observed ground magnetic disturbance. However, the assumption for the infinite sheet current approximation is far from realistic, underestimating the current density. And the correlation between ${\Delta}H$ and J/sub E/ is higher than the one between ${\Delta}D$ and J/sub N/ , indicating that field-aligned current affects significantly ${\Delta}D$.

• Polymer(Korea)
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• v.39 no.2
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• pp.338-345
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• 2015

Poly(phenylene oxide) (PPO) and polyether imide (PEI) were sulfonated and aminated to create sulfonated poly(phenylene oxide) (SPPO) and aminated polyether imide (APEI), respectively. Characterization of the SPPO and APEI were performed via measurements of FTIR, thermogravimetry (TGA), swelling degree, ion exchange capacity (IEC), and ion conductivity. Next, the surfaces of these membranes were modified by surface fluorination at room temperature. The surface fluorinated SPPO and APEI membranes underwent characterization again for the mentioned measurements to determine any differences. The 3 types of bi-polar membranes were prepared by varying the IEC of the APEI at a fixed SPPO IEC value, which were applied to the low and high NaCl concentration of feed solution at the different current density, respectively. The hypochlorite concentration derived from the surface fluorinated membranes was dependent on the IEC of the APEI and ranged from 491 to 692 ppm at $80mA/m^2$. At low current density of $5mA/m^2$, the hypochlorite concentrations ranged from 18 to 28 ppm for the 4 hrs surface fluorinated membranes and their durability increased greatly.