• Korean Journal of Materials Research
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• v.31 no.1
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• pp.16-22
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• 2021

In this study, quantum dot-sensitized solar cells (QDSSC) using CdSe/ZnS quantum dots (QD) of various sizes with green, yellow, and red colors are developed. Quantum dots, depending their different sizes, have advantages of absorbing light of various wavelengths. This absorption of light of various wavelengths increases the photocurrent production of solar cells. The absorption and emission peaks and excellent photochemical properties of the synthesized quantum dots are confirmed through UV-visible and photoluminescence (PL) analysis. In TEM analysis, the average sizes of individual green, yellow, and red quantum dots are shown to be 5 nm, 6 nm, and 8 nm. The J-V curves of QDSSC for one type of QD show a current density of 1.7 mA/㎠ and an open-circuit voltage of 0.49 V, while QDSSC using three type of QDs shows improved electrical characteristics of 5.52 mA/㎠ and 0.52 V. As a result, the photoelectric conversion efficiency of QDSSC using one type of QD is as low as 0.53 %, but QDSSC using three type of QDs has a measured efficiency of 1.4 %.

• Asian Journal of Innovation and Policy
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• v.11 no.1
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• pp.1-29
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• 2022

Climate action is at the top of the agenda in the international community, as demonstrated at the 2021 G7 Summit and the 2021 UN Climate Summit. Major developed countries are scrambling to make a transition to a green economy and create a new growth momentum. Following the Paris Climate Agreement in 2016, they focus on "carbon neutrality" as an effective means of tackling climate change. The Republic of Korea, a high-carbon economy, submitted its second Nationally Determined Contribution and announced carbon neutrality as a top policy priority. Accordingly, the country increases government budget in research and development (R&D) and science and technology (S&T) policies. Against this backdrop, this study analyzed policies on carbon-neutral S&T and R&D in major advanced countries. The analysis was made by identifying globally pending issues in carbon-neutral policies and climate technology. In addition, focus group interviews were conducted six times with 10 experts to come up with three R&D strategies and action plans for government-funded research institutes to achieve carbon neutrality. To be specific, the following measures were suggested. First, creative and innovative R&D programs are required to solve the problem of carbon emissions. Second, it is necessary to establish carbon neutrality policies and infrastructure which are sustainable to run and manage. Third, it is crucial to promote cooperation in climate technology based on excellence. In conclusion, the strategies proposed in this study are expected to provide directions and implications for policymakers, researchers, and scholars in science and technology to develop effective strategies to achieve national carbon neutrality.

• Korean Journal of Materials Research
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• v.33 no.7
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• pp.315-322
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• 2023

In the present work, we address the new route for the green synthesis of manganese dioxide (MnO₂) by an innovative method named the solution plasma process (SPP). The reaction mechanism of both colloidal and nanostructured MnO₂ was investigated. Firstly, colloidal MnO₂ was synthesized by plasma discharging in KMnO₄ aqueous solution without any additives such as reducing agents, acids, or base chemicals. As a function of the discharge time, the purple color solution of MnO₄^- (oxidation state +7) was changed to the brown color of MnO₂ (oxidation state +4) and then light yellow of Mn²⁺ (oxidation state +2). Based on the UV-vis analysis we found the optimal discharging time for the synthesis of stable colloidal MnO₂ and also reaction mechanism was verified by optical emission spectroscopy (OES) analysis. Secondly, MnO₂ nanoparticles were synthesized by SPP with a small amount of reducing sugar. The precipitation of brown color was observed after 8 min of plasma discharge and then completely separated into colorless solution and precipitation. It was confirmed layered type of nanoporous birnessite-MnO₂ by X-ray powder diffraction (XRD), fourier-transform infrared spectroscopy (FT-IR), and electron microscopes. The most important merits of this approach are environmentally friendly process within a short time compared to the conventional method. Moreover, the morphology and the microstructure could be controllable by discharge conditions for the appropriate potential applications, such as secondary batteries, supercapacitors, adsorbents, and catalysts.

• Journal of the Korean earth science society
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• v.34 no.3
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• pp.209-223
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• 2013

The purpose of this study was to estimate the contributed concentration of each emission source to $CH_4$ by verifying the simulated concentration of $CH_4$ in the Korean peninsula, and then to compare the $CH_4$ emission used to the $CH_4$ simulation with that of a box model. We simulated the Weather Research Forecasting-Community Multiscale Air Quality (WRF-CMAQ) model to estimate the mean concentration of $CH_4$ during the period of April 1 to 22 August 2010 in the Korean peninsula. The $CH_4$ emissions within the model were adopted by the anthropogenic emission inventory of both the EDGAR of the global emissions and the GHG-CAPSS of the green house gases in Korea, and by the global biogenic emission inventory of the MEGAN. These $CH_4$ emission data were validated by comparing the $CH_4$ modeling data with the concentration data measured at two different location, Ulnungdo and Anmyeondo in Korea. The contributed concentration of $CH_4$ estimated from the domestic emission sources in verification of the $CH_4$ modeling at Ulnungdo was represented in about 20%, which originated from $CH_4$ sources such as stock farm products (8%), energy contribution and industrial processes (6%), wastes (5%), and biogenesis and landuse (1%) in the Korean peninsula. In addition, one that transported from China was about 9%, and the background concentration of $CH_4$ was shown in about 70%. Furthermore, the $CH_4$ emission estimated from a box model was similar to that of the WRF-CMAQ model.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.253-259
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• 2012

Disposal of high amount of coal combustion by-products, such as fly ash and bottom ash, is of a great concern to the country, due to the huge treatment cost and land requirement. On the other hand, those coal-ash wastes are considered to have desirable characteristics that may improve physical, chemical, and biological properties of soils. Especially, compared with fly ash, bottom ash has a larger particle size, porous surface area, and usable amount of micronutrients. In the present study, we examined bottom as a soil amendment for mitigating $CO_2$ emission and enhancing carbon sequestration in soils fertilized with organic matter (hairy vetch, green barely, and oil cake fertilizer). Through laboratory incubation, $CO_2$ released from the soil was quantitatively and periodically monitored with an enforced-aeration and high-temperature respirometer. We observed that amendment of bottom ash led to a marked reduction in $CO_2$ emission rate and cumulative amount of $CO_2$ released, which was generally proportional to the amount of bottom ash applied. We also found that the temporal patterns of $CO_2$ emission and C sequestration effects were partially dependent on the relative of proportion labile carbon and C/N ratio of the organic matter. Our results strongly suggest that amendment of bottom ash has potential benefits for fixing labile carbon as more stable soil organic matter, unless the bottom ash contains toxic levels of heavy metals or other contaminants.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.65-65
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• 2015

In this talk, I will introduce two topics. The first topic is the polymer light emitting diodes (PLEDs) using graphene oxide quantum dots as emissive center. More specifically, the energy transfer mechanism as well as the origin of white electroluminescence in the PLED were investigated. The second topic is the facile synthesis of eco-friendly III-V colloidal quantum dots and their application to light emitting diodes. Polymer (organic) light emitting diodes (PLEDs) using quantum dots (QDs) as emissive materials have received much attention as promising components for next-generation displays. Despite their outstanding properties, toxic and hazardous nature of QDs is a serious impediment to their use in future eco-friendly opto-electronic device applications. Owing to the desires to develop new types of nanomaterial without health and environmental effects but with strong opto-electrical properties similar to QDs, graphene quantum dots (GQDs) have attracted great interest as promising luminophores. However, the origin of electroluminescence (EL) from GQDs incorporated PLEDs is unclear. Herein, we synthesized graphene oxide quantum dots (GOQDs) using a modified hydrothermal deoxidization method and characterized the PLED performance using GOQDs blended poly(N-vinyl carbazole) (PVK) as emissive layer. Simple device structure was used to reveal the origin of EL by excluding the contribution of and contamination from other layers. The energy transfer and interaction between the PVK host and GOQDs guest were investigated using steady-state PL, time-correlated single photon counting (TCSPC) and density functional theory (DFT) calculations. Experiments revealed that white EL emission from the PLED originated from the hybridized GOQD-PVK complex emission with the contributions from the individual GOQDs and PVK emissions. (Sci Rep., 5, 11032, 2015). New III-V colloidal quantum dots (CQDs) were synthesized using the hot-injection method and the QD-light emitting diodes (QLEDs) using these CQDs as emissive layer were demonstrated for the first time. The band gaps of the III-V CQDs were varied by varying the metal fraction and by particle size control. The X-ray absorption fine structure (XAFS) results show that the crystal states of the III-V CQDs consist of multi-phase states; multi-peak photoluminescence (PL) resulted from these multi-phase states. Inverted structured QLED shows green EL emission and a maximum luminance of ~45 cd/m2. This result shows that III-V CQDs can be a good substitute for conventional cadmium-containing CQDs in various opto-electronic applications, e.g., eco-friendly displays. (Un-published results).

• Journal of the Korea Organic Resources Recycling Association
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• v.20 no.3
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• pp.27-33
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• 2012

According to the statistics of the Ministry of Environment, the emission of sewage sludge is increased by 7~9% yearly. In the future, it will be increased continuously because of extension of sewage disposal plants, high class treatment for removing nitrogen and phosphorus. Until now, we have depended on reclamation for lots of quantity and some part has been treated by ocean emission. But, direct reclamation of organic waste will be prohibited and even ocean emission will be prohibited now, so the treatment of sludge is put on emergency alert. Bio-gas can be produced by applying anaerobic digestion method for the recycling or refuse derived fuel can be conducted by applying carbonization method. However, the process is difficult, causes bad smell and makes it the second waste, so it cannot be practical method in fact. This study applied a fluidized bed combustor for sewage sludge treatment technologies that can actually take advantage of key technologies in order to verify its purpose is to demonstrate selected. If applying the fluidized bed combustor, it can be easily utilized as the replaced resource of energy(fuel) in the countries whose energy resources are insufficient, like our country. Especially, if applying only original strengths of the fluidized bed combustor sufficiently, the sewage sludge can be treated simply, eco-friendly, sanitarily and economically. Particularly, it is verified as the energy technology suitable for government's green growth policy.

• Journal of the Korea Organic Resources Recycling Association
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• v.22 no.1
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• pp.40-48
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• 2014

Due to increasing greenhouse gas emissions, global warming and abnormal weather phenomena it has become important on a national level to keep a count of greenhouse gases being emitted. We want to take advantage of any selected area, as the basic data for the calculation of greenhouse gas emissions, Forest and Grassland, Paddy fields, and Fields(crops), Greenhouse(crops), Pig farm, Cattle farm, Farm household(populations, agricultural machinery) and Vehicle, the basic building blocks shots with a small amount of per-unit basis, the statistics calculated based on regional carbon emissions through the literature and experimental. Carbon absorption 772,960 ton C/year, amount of fixation 487,477 ton C/year, amount of emission 1,112,607 ton C/year were noted in Gimje-si, and amount of carbon absorption 55,559 ton C/year, amount of fixation 25,864 ton C/year, amount of emissions 58,355 ton C/year in Gongdeok-myeon, respectively. The carbon absorption at Hwangsan-ri is 25,107 ton C/year, fixation 4,301 ton C/year, and emission 20,330 ton C/year respectively. We were able to estimate the amount of carbon according to the specific characteristics of each unit village, then expanding it to a large-scale and comparative analysis, therefore we were able to obtain basic data on the national levels of carbon absorption.

• Korean Journal of Construction Engineering and Management
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• v.12 no.6
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• pp.110-119
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• 2011

Global warming caused by excessive greenhouse gas emission is causing climate change all over the world. In Korea, greenhouse gas emission from residential buildings accounts for about 10% of gross domestic emission. Also, the number of deteriorated multi-family housing complexes is increasing. Therefore, the goal of this research is to establish the bases to manage energy consumption continuously and methodically during MR&R period of multi-family housings. The research process and methodologies are as follows. First, research team collected the data on project characteristics and energy consumption of multi-family housing complexes in Seoul. Second, an ontology-based breakdown structure was established with some primary characteristics affecting the energy consumption, which were selected by statistical analysis. Finally, a predictive model of energy consumption was developed based on the ontology-based breakdown structure, with application of CBR, ANN, MRA and GA. In this research, PASW (Predictive Analytics SoftWare) Statistics 18, Microsoft EXCEL, Protege 4.1 were utilized for data analysis and prediction. In future research, the model will be more continuous and methodical by developing the web-base system. And it has facility manager of government or local government, or multi-family housing complex make a decision with definite references regarding moderate energy consumption.

• Journal of Environmental Policy
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• v.8 no.4
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• pp.95-124
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• 2009

This study aims to introduce greenhouse gas emission trading in Korea as a highly cost-effective mechanism for controlling emissions. The Basic Act on Low-Carbon Green Growth will cover methods of emissions allocation, national inventory, and trading systems (i.e. emissions trading platforms, national registry,and clearing and settlement platforms). The Korean emission scheme will be based on the Korean Climate Change Act proposed by the National Assembly and Government with a cap-and-trade scheme. The national allowances will be allocated by the hybrid system. To establish the national inventory, TRADEMARKS (Telemetering System) and emissions factors are effective for greenhouse gas emissions measurement. It will likewise be effective for the national registry to be implemented via a Korean Integrated Registry, the emissions trading platform via the KRX (Korean Exchange), and the clearing and settlement platform via the KSD (Korean Securities Depository). In other words, the KRX will manage product development and marketing for Korean Carbon Financial Instruments (including commodities, futures, and options contracts) listed and admitted to trading on the KRX. All emissions trades will be standardized and cleared by the KSD.