• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.3
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• pp.127-138
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• 2016

Diesel vehicles should be equipped with urea-selective catalytic reduction(SCR) system as a high-performance catalyst, in order to reduce harmful nitrogen oxide emissions. In this study, a three-dimensional Eulerian-Lagrangian CFD analysis was used to numerically predict the multiphase flow characteristics of the urea-SCR system, coupled with the chemical reactions of the system's transport phenomena. Then, the numerical spray structure was modified by comparing the results with the measured values from spray visualization, such as the injection velocity, penentration length, spray radius, and sauter mean diameter. In addition, the analysis results were verified by comparison with the removal efficiency of the nitrogen oxide emissions during engine and chassis tests, resulting in accuracy of the relative error of less than 5%. Finally, a verified CFD analysis was used to calculate the interanl flow of the urea-SCR system, thereby analyzing the characteristics of pressure drop and velocity increase, and predicting the uniformity index and overdistribution positions of ammonia.

• Journal of the Korea Institute of Building Construction
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• v.18 no.5
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• pp.419-427
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• 2018

The purpose of this study is to recycle steel slag generated from the iron producing process and to use steel slag as a construction material which is currently landfilled Steel slag is subjected to aging treatment due to the problem of expansion and collapse when it reacts with water. The Slag Atomizing Technology (SAT) method developed to solve these problems of expanding collapse of steel slag. In this study, experimental study on the emergency repair mortar using the reducing slag, electric arc furnace slag and silicon manganese slag manufactured by the SAT method is Reduced slag was shown an accelerated hydration when it was replaced with rapidly-setting cement, and the rate of substitution was equivalent to 15%. It is shown that the electric furnace oxide slag is equivalent to 100% of the natural aggregate, and it can be replaced by 15-30% when the silicon manganic slag is substituted for the electric furnace oxide slag. With the above formulation, it was possible to design the rapidly repair mortar for road use. These recycling slags can contribute on achieving sustainability of construction industry by reducing the use of cement and natural aggregates and by reducing the generation of carbon dioxide and recycling waste slag.

• Korean Journal of Food Science and Technology
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• v.50 no.2
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• pp.172-178
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• 2018

The sterilization rates were investigated to develop effective pretreatment methods of garlic and ginger using antimicrobial agents and blanching. Antibacterial components in chopped garlic and ginger, such as allicin, ginger, and shogaol, exhibited an antibacterial effect that reduced bacteria by a factor of $10^1(CFU/g)$. The total number of bacteria in garlic and ginger was decreased by $10^1(CFU/g)$ after individually soaking in 1% (w/w) citric acid, calcium oxide and 200 ppm sodium hypochlorite solution for 1 h, respectively. When chopped garlic and ginger were immersed in 1% (w/w) calcium oxide solution for 1 h, the bactericidal effect was increased by $10^4-fold$. Total cells with thermoduric bacteria exhibited a $10^3-10^4-fold$ reduction after heating for 30-40 s at $90-95^{\circ}C$. The combination of soaking in 200 ppm sodium hypochlorite solution and blanching at $95^{\circ}C$, 40 s showed $10^1-fold$ decrease in total number of cells compared to blanching in whole ginger.

• Applied Chemistry for Engineering
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• v.5 no.2
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• pp.327-336
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• 1994

The synergistic effects in mechanical mixture catalysts of Mo-V-O and metal oxide were investigated for the selective oxidation of acrolein. The metal oxides used are $SnO_2$, ${\alpha}-Sb_2O_4$, $WO_3$, ${\alpha}-Al_2O_3$, CuO, $MnO_2$, $Cu_2O$, MgO, CoO, and ZnO. Mechanical mixtures of Mo-V-O plus $SnO_2$ or ${\alpha}-Sb_2O_4$ had resulted in higher conversion of acrolein and higher yield of acrylic acid than Mo-V-O. The origin of the synergy is attributed to the cooperation of Mo-V-O and $SnO_2$ or ${\alpha}-Sb_2O_4$, in which $SnO_2$ or ${\alpha}-Sb_2O_4$ forms dissociated oxygens at their oxygen vacancies and transports them to Mo-V-O. $Cu_2O$, MgO, CuO, and $MnO_2$, increased conversion of acrolein but decreased yield of acrylic acid. CoO and ZnO inhibited the catalytic performance of Mo-V-O. The different role of these metal oxides is explained in terms of their oxidation-reduction properties.

• Korean Journal of Agricultural and Forest Meteorology
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• v.21 no.4
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• pp.307-316
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• 2019

In the agricultural sector, greenhouse gas emissions vary depending on the interaction of all ecosystem changes such as soil environment, weather environment, crop growth, and anthropogenic farming activities. Agricultural sector greenhouse gas emissions resulting from many of these interactions are highly variable. Uncertainty-based evaluation that defines the interval with confidence level of greenhouse gas emission and absorption is necessary to take account of the variance characteristics of individual emissions, but research on uncertainty evaluation method is insufficient. This study aims to decide on the effect of reducing N₂O emissions from upland soils using an uncertainty-based approach. An uncertainty-based approach confirmed whether there was a difference between confidence intervals in the 5 different fertilizer treatment groups to reduce greenhouse gas emissions. Unlike the statistically significant test with three repetition averages, the uncertainty-based approach method estimated in this study is able to estimate the confidence interval considering the distribution characteristics of the emissions, such as the dispersion characteristics of individual emissions. Therefore, it is considered that the reliability of emissions can be improved by statistically testing the variance characteristics of emissions such as the uncertainty-based approach. It is hoped that the direction of the uncertainty-based approach for the effect of reducing greenhouse gas emissions in agriculture will be helpful in the future development of agricultural greenhouse gas emission reduction technology, adaptation to climate change, and further development of sustainable eco-social system.

• Journal of Life Science
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• v.27 no.7
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• pp.783-789
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• 2017

Malus melliana (Hand.-Mazz.) Rehder (M. melliana) is a Chinese plant that belongs to the Rosaceae family. There have been no previous reports regarding its bioactivity. In this study, the anti-oxidative and anti-inflammatory activities of M. melliana ethanol extract (MMEE) were evaluated using a 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging activity assay, reactive oxygen species (ROS) scavenging activity assay, nitric oxide (NO) inhibitory activity assay, and the analysis of related protein expressions through Western blot hybridization. MMEE showed potent scavenging activity against DPPH, similar to ascorbic acid, a well-known anti-oxidative agent, which was used as a positive control. MMEE also inhibited hydrogen peroxide-induced ROS in RAW 264.7 cells. Moreover, MMEE induced the expression of an anti-oxidative enzyme, heme oxygenase 1, and its upstream transcription factor, nuclear factor E2-related factor-2, in a dose-dependent manner. On the other hand, MMEE was associated with a reduction in NO production, which was induced by the lipopolysaccharide treatment of RAW 264.7 cells. The expression of inducible nitric oxide synthase, which is the upstream regulator of NO production, was also inhibited. Taken together, these results suggest that MMEE has anti-oxidative and anti-inflammatory properties, thus appearing to be a potential anti-oxidant and anti-inflammatory agent. The further identification of active compounds that confer the biological activities of MMEE may be necessary.

• Polymer(Korea)
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• v.36 no.5
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• pp.656-661
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• 2012

The palladium nanoparticles were self-assembled to make Pd-POSS using POSS-$NH_3{^+}$ (polyhedral oligomeric silsesquioxane) as a crosslinker. Graphene oxide (GO) was produced by the reaction of graphite under a strong acid and oxidizer and poly(acrylic acid) (PAA) was covalently grafted on the surface of graphene to make PAA-grafted graphene through the radical polymerization of acrylic acid and GO along with a reduction process under $NaBH_4$. The nanocomposites of Pd-POSS and PAA-grafted graphene were fabricated via ionic interactions between positively charged Pd-POSS and negatively charged PAA-grafted graphene. Pd-POSS nanoparticles were attached to the surface of PAA-grafted graphene through ionic interactions. The thermal stability of Pd-POSS/PAA-grafted graphene was higher than that of PAA and PAA-grafted graphene. The composition, structure, surface morphology, and thermal stability of the Pd-POSS/PAA-grafted graphene were studied by FE-SEM, AFM, TEM, FTIR, and TGA.

• Food Science and Preservation
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• v.14 no.4
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• pp.419-424
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• 2007

Fruits and vegetable extracts are well-known as healthy foods. Such foods have been used as herbal medicines or traditional therapies for centuries. To assess biological activities in grapes, we examined the immunomodulating activities of water extracts from four kinds of grapes (cultivars Kyoho, Delaware, Campbell, and Niagara). We explored possible antioxidant and anticancer activities using antioxidant assays such as the 1,1-diphenyl-2-picrylhydrazyl (DPPH) reduction assay, the ferric iron reducing ability of plasma (FRAP) assay, a cell proliferation assay, an NO inhibition assay, a wound healing assay, and an IL-4/IL-13 elicitation assay. Methanol extracts of grapes were tested. The results showed that each grape extract had potent antioxidant activities. The grape extracts increased cell proliferation and NO production activities in tumor cell lines. IL-4 and IL-13 cytokine levels were decreased in mouse primary spleen cells by treatment with any extract. These results suggest that grape extracts can be used as biomaterials with immunomodulating activities.

• Polymer(Korea)
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• v.38 no.6
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• pp.687-693
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• 2014

Poly(ether-block-amide) 1657 (PEBAX 1657) blended membranes with molecular weight 400 poly(ethylene glycol) (PEG 400) were prepared and their permeability was tested for the gases $N_2$, $O_2$, $CH_4$, $CO_2$, and $SO_2$ by the time-lag method. The permeation characteristics were investigated in terms of diffusivity and solubility, which are dominant factors for gas transport. With the addition of PEG 400, the permeability of all the gases increased and also the ideal selectivity for several pair gases was enhanced. In particular, selectivity for $CO_2/N_2$ ranged from 53.2 (pristine PEBAX 1657 membrane) to 84.1 (50% PEG 400 added), for $SO_2/CO_2$ from 38.9 to 50.7, and for $CO_2/CH_4$ from 17.7 to 31.4. The increase of both permeability and selectivity is mainly because of the increase of solubility of the gases, especially $CO_2$ and $SO_2$. To obtain durability against water vapor, glutaraldehyde (GA) was added to the PEBAX 1657/PEG 400 blended membranes. As a result, permeability decreased owing to a reduction of the free volume and ether oxide units, which are the main factors in elevating the permeability for the blended membranes, and selectivity decrease however; we believe that the durability of the resulting membranes would be increased.

• Journal of the Korean Vacuum Society
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• v.12 no.4
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• pp.239-250
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• 2003

The reliability degradation phenomena in the SiGe hetero-junction bipolar transistor (HBT) are investigated in this review. In the case of the SiGe HBT the decrease of the current gain, the degradation of the AC characteristics, and the offset voltage are frequently observed, which are attributed to the emitter-base reverse bias voltage stress, the transient enhanced diffusion, and the deterioration of the base-collector junction due to the fluctuation in fabrication process, respectively. The reverse-bias stress on the emitter-base junction causes the recombination current to rise, increasing the base current and degrading the current gain, because hot carriers formed by the high electric field at the junction periphery generate charged traps at the silicon-oxide interface and within the oxide region. Because of the enhanced diffusion of the dopants in the intrinsic base induced by the extrinsic base implantation, the shorter distance between the emitter-base junction and the extrinsic base than a critical measure leads to the reduction of the cut-off frequency ($f_t$) of the device. If the energy of the extrinsic base implantation is insufficient, the turn-on voltage of the collector-base junction becomes low, in the result, the offset voltage appears on the current-voltage curve.